Model Test Paper

Bile juice is secreted by gall bladder present in the liver. It is released into the small intestine through the hepato-pancreatic duct. Bile juice helps in the digestion of food by helping in the digestion of fats. Bile juice contains two major components that are, bilirubin and biliverdin. Bile juice helps in digestion of food as:

1. Breaking down larger fat globules into smaller ones so, that pancreatic enzymes can act on it. This is called emulsification of fats.

2. It decreases the acidic nature of food coming out from the stomach (acidic due HCl) due to its alkaline nature due to, NaHCO₃ hence, decreasing the chances of acidity.

3. It helps in the activation of lipase.

Yes, the chromosome number of the zygote, embryonic cells, and adult of a particular organism is always constant because of mitosis/equational division and meiosis/reductional division.

This is done as follows gametes are formed by the meiosis during the process of gametogenesis. As a result chromosome gets reduced into half. When these gametes fuse, that is, at the time of fertilization, the number of chromosomes becomes equal to that in a somatic cell. After this, when cells multiply due to mitosis, the number of cells become consistent.

For example: In the case of humans, they contain 2n = 46 chromosomes in their somatic cell. Now when meiosis takes place, the number of chromosomes in gametes become n = 23. When fertilization takes place, the gametes fuse to form a zygote with ploidy n+n = 2n that is, 46 chromosome. Hence, maintaining the constancy in these three stages.

Modern Periodic Law states that the physical and chemical properties of elements are the periodic functions of their atomic number.

Number of groups = 18

Number of periods = 7

Four characteristics of images formed by a plane mirror are:

* Size of the object is always equal to the size of images formed.

* The image formed is virtual and erect.

* The image is laterally inverted.

* The distance between the object and mirror is equal to the distance between the mirror and image.

Charcoal is obtained from wood by burning the wood in a limited supply of oxygen. During this water along with the volatile components gets evaporated and charcoal is left behind as a residue.

Charcoal is considered a better fuel than wood because:

* Charcoal has the highest heat generation efficiency.

* Charcoal as compared to the wood produces less smoke.

* Charcoal leaves very less residue behind.

* Charcoal burns without flames.

i. When lead nitrate reacts with potassium iodide, it forms a yellow coloured precipitate of lead iodide along with potassium nitrate.

ii. This type of reaction is a double displacement reaction.

iii. [PbNO₃]₂ + 2KI → 2KNO₃ + PbI₂

Here,

PbNO₃ is lead nitrate.

KI is potassium iodide.

KNO₃ is potassium nitrate.

PbI₂ is lead iodide.

OR

i. X is Cu.

Y is CuO.

ii. This a redox chemical reaction. Here, copper gets oxidised by heating to copper oxide, and hydrogen reduces copper oxide back to copper.

iii. Cu + O₂ → 2CuO

CuO + H₂ → Cu + H₂O

A is NaHCO₃ used in the bakery.

B is Na₂CO₃ used in the removal of hardness.

C is CO₂ turns lime water milky.

2NaHCO₃ + O₂(HEATING) → Na₂CO₃ + CO₂ + H₂O

i. When elements are arranged in increasing order of their atomic number, elements repeat its property after certain elements, this repetition of the property is called periodicity of properties.

ii. Elements of the same group have the same properties because of:

1. A same number of valence electrons in the outermost shell.

2. Same valency

Examples: 1) In group 1 of alkali metals they all (Li, Na, K, Rb, Cs, Fr) have similar property due to the same number of valence electrons (equal to 1) and valency (equal to 1).

2) In group 17 of alkali metals, they all (F, Cl, Br, I ) have similar property due to the same number of valence electrons (equal to 7) and valency (equal to 1).

This plant will not live for long with leaves coated with Vaseline to block stomata because:

√ No photosynthesis takes place as no sunlight is received by the plant.

√ No transpiration as water is not able to evaporate or ooze out of stomata.

√ No respiration as no intake of carbon dioxide takes place.

OR

i. Fish respire with a specialized organ called gills. Gills are richly supplied with blood capillaries and readily absorb oxygen from water. When fish is taken out of the water, the walls of gills collapse. As a result, it is not able to take oxygen from air and hence, die due to oxygen deficiency.

ii. Aquatic organisms are those who live in water and breathe using oxygen dissolved in water. Terrestrial organisms are those who live on land and breathe oxygen directly from the atmosphere. As the amount of oxygen is less in water as compared to land, this is the reason why aquatic animal breathe faster than a terrestrial animal so that it can acquire more amount of oxygen.

i. a. Testis: It is responsible for the generation of sperms. Also, it is responsible for making testosterone (primary male sex hormone).

ii.Vas deferens: It transports mature sperm to the urethra.

iii. Urethra: It is responsible for ejaculation of sperm to the outside of the body when a male reaches orgasm.

iv. Prostrate gland: It provides fluidity to semen and helps in the nourishment of sperms.

Two common pubertal changes in the male are: Growing of facial hair and broadening of voice box that is, Adam’s apple which leads to hoarseness of voice.

Humans have two different types of sex chromosomes and hence, said to have heterogamy. Human male has chromosome XY and female has chromosome XX. That means, humans male have two types of gametes that is, X and Y and female has gametes with only X chromosome.

Now, if male gamete is having chromosome X fuses with ovum having chromosome X, this results into a female child.

And, if male gamete is having chromosome Y fuses with ovum having chromosome X, this results into a male child.

Male has 22 pairs of allosome and 1 pair of sex chromosome XY that is 44 + 2 = 46 chromosomes.

Female has 22 pairs of allosome and one pair of sex chromosome XX that is 44 + 2 = 46 chromosomes.

A number of chromosome of a particular organism is always constant because of mitosis/equational division and meiosis/reductional division.

This is done as follows gametes are formed by the meiosis during the process of gametogenesis. As a result chromosome gets reduced into half. When these gametes fuse, that is, at the time of fertilization, the number of chromosomes becomes equal to that in a somatic cell. After this, when cells multiply due to mitosis, the number of cells become consistent.

For example: In the case of humans, they contain 2n = 46 chromosomes in somatic cell. Now when meiosis takes place, the number of chromosomes in gametes become n = 23. When fertilisation takes place, the gametes fuse to form a zygote with ploidy n+n = 2n that is, 46 chromosome. Hence, maintaining the constancy in these three stages.

the Convex lens is a converging lens. It forms a virtual and erect image when the object lies between the optical center and focus.

(i) As, V = IR

If, I = 1A and R = 1Ω then, V = 1V

The difference of potential that would carry one ampere of current against one-ohm resistance.

(ii) According to the definition, the potential difference between two points is defined as the amount of work done in moving charge from one point to another.

So, Potential difference =

V =

For, work done = 100J and charge = 20C

V =

=

= 5J

OR

(i) I =

If, I = 1A and t = 1s then, q = 1C.

Coulomb is that amount of electric charge required by one ampere current in unit time.

(ii) I =

For, I is electric current, q is electric charge, and t is time.

Now, I = 200m A and t = 20min

200 × 10^-3 =

0.2 × 1200 = q

240C = q

Direction of current can be calculated by right-hand thumb rule.

According to this rule, thumb denotes the direction of current and fingers are curled in the direction where the magnetic field needs to be find out.

By this magnetic field at P is inside the paper and at Q is outside. Magnet field at Q is larger than at P as the distance is inversely proportional to the magnetic field.

(i) IONIC COMPOUND: (a) Formed due to the electrostatic force of attraction that is, electrovalent bond.

(b) Soluble in polar solvents like water as it readily forms ions but not soluble in non-polar solvents like benzene.

(c) Conduct electricity only in a molten state as it forms ions.

COVALENT COMPOUND: (a) Has covalent bond between constituents due to polarity.

(b) Soluble in non-polar solvents like benzene as it readily forms ions but not soluble in polar solvents like water.

(c) Does not conduct electricity.

(ii) There are two main methods of extracting metals from their ores:

* reduction with carbon

* electrolysis

The method used to extract a metal from their compounds depends upon the stability of its compound in the ore. And, the stability of the ore depends on upon the reactivity of the metal. The following diagram shows the brief methods for extraction.

(a) Metal M which is in the middle of the reactivity series –

The metals less reactive than carbon can be extracted from their ores by reduction.

For example, the extraction of lead from lead oxide:

(b) Metal N which is high up in the reactivity series –

Metals above carbon in the reactivity series must be extracted using electrolysis.
For example, when an electric current is passed through molten state or solution of sodium chloride, sodium metal deposited over the cathode.

Na⁺ + e− ⇒ Na

2Cl⁻ − e− ⇒ Cl2

2NaCl ⇒ 2Na + Cl2

Metals obtained from the process of electrolytic reduction are pure in form.

OR

(i) Roasting: When sulphide containing ore is heated for a long time in the presence of an excess of air to form a metal oxide, this method of converting sulphide containing ore into metal oxide in the presence of an excess of air is called roasting.

e.g.,

Calcination: When carbonate containing ore is heated for a long time in the absence of air it is converted into metal oxide. This method of converting carbonate containing ore into metal oxide is called calcination.

e.g.,

(ii)Write a chemical equation to illustrate the use of aluminum for joining cracked railway lines.

Thermite reaction used for the welding of rails (joining metals) called as thermite welding.

This is an exothermic reaction which includes the igniting aluminum and ferric oxide.

Fe₂O₃ (s) + Al (s) →Al₂O₃ + 2 Fe(l) + Heat

Iron obtained in this process is in a molten state.

(iii) Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure copper.

In the method of electrolysis, the rod of impure metal is taken as anode and rod of pure metal is taken as a cathode. The aqueous solution of a salt of, metal is used as an electrolyte. On passing electric current the anode dissolves in the electrolyte, and the same proportion of pure metal gets deposited on the cathode.

Refining of copper by electrolysis

Salt X is sodium ethanoate and the evolved gas is carbon dioxide.

The reaction is given below:

CH₃COOH + NaHCO₃ → CH₃COONa + H₂CO₃

Activity:

(a) Take a test tube and a bent tube.

(b) Take ethanoic acid and sodium bicarbonate solution in the test tube.

(c) Insert the bent tube in the cork and fit the cork at the mouth of the test tube.

(d) Fill lime water in the bent tube so that lime water is in the ‘U’ portion of this tube.

After some time; it is observed that the lime water turns milky. This confirms that the evolved gas is carbon dioxide. The diagram is given below:

Involuntary Action: These actions occur without the thinking of a person or his conscious.

The brain controls it.

Example: Churning of stomach, heartbeat.

Reflex action: Spontaneous action for any stimulus.

It is controlled by the spinal cord.

Example: knee-jerk when the hammer strikes knee.

OR

Signals in a synapse from the axonal end of one neuron to dendritic end of another neuron but not the reverse is because of the chemicals/ neurotransmitter released at the axonal end where electric signals get converted to chemical signals. These neurotransmitters from axonal end move towards dendrites of another neuron, and hence, the signal gets transmitted.

(i) Myopia or near sightedness where a person can see the objects near to him but cannot see farther objects distinctly.

CAUSES: 1. Decreases in focal length of the eye lens.

2. Elongation of the eyeball.

(ii) Human eye lens tends to adjust the focal length he/she can see this is called accommodation of eye lens. This accommodation lies between 25cm to infinity.

A person can’t focus at 10cm because it lies outside the range of accommodation and focusing on this length may have bad impact on eyes that is a strain.

A fuse in a circuit prevents damage to the appliances and the circuit due to overloading.

Importance of fuse: When the current exceeds the value of fuse rating, the fuse wire melts down as a result circuit gets broken up and current can’t move forward and hence, protecting the appliances.

Some harmful effects of agricultural practices on the environment are:

* The process of farming involves growing of a particular set of species as a result of which many other species may get eradicated. This leads to biodiversity loss.

* Availability of land for agriculture is done by deforestation that is, clearing of forests.

* Due to repeated farming nutrients are lost by soil which is called soil degradation, and gradually it leads to desertification that is, turning of fertile soil into a barren desert.

* Biodiversity loss and usage of groundwater results in a decrease of ground water level.

* Fertilisers and pesticides lead to soil pollution.

No change in the colour of pH paper takes place because sodium carbonate in solid does not have free ions. Change in colour only occurs when sodium carbonate would be in the aqueous form as free ions will be present which results in a change of colour.

Soft water when mixed with soap or detergent forms lather but hard water when mixed with soap water does not form lather but form scum, but with detergent, it forms a lather.

OR

CH₃COOH + NaHCO₃ → CH₃COONa + H₂CO₃ → CH₃COONa + H₂O + CO₂↑

CO₂ turns lime water milky.

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

In set up A, the water rise as the rubber cork perfectly seals the conical flask hence creating the vacuum but in set up B due to cotton plug as cotton cannot perfectly seal the flask, and air can pass through as a result water does not rise up as water needs perfect vacuum to rise up.

Type of asexual reproduction in which two individuals are formed from a single parent and parental identity is lost is binary fission.

First step: Elongation of nucleus and cytoplasm.

(i) Incident Ray

(ii) Angle of Deviation

(iii) Normal for emergent ray.

(iv) Emergent Ray

Potential energy = Current × Resistance

V = I × R

1.8V = 180m A × R

1.8V = 0.18A × R

= R

10Ω = R

In plants, xylem is a water-conducting tissue. The main work of xylem is that it moves water from minerals which are obtained from the soil. It transports water to the different parts of the plant.

If the xylem of a plant is removed:

i. Bending of leaves will be stopped due to the upward movement of water.

ii. Due to the absence of water (upward movement of water), plants will not remain for a long time, and this can cause the death of a plant.

Colonies of yeast fail to multiply in water, but multiple in sugar solution because:

i. In the presence of water, yeast is not able to multiply as there is no source of food for them.

ii. On the other hand, in the presence of sugar solution, yeast is able to multiply as sugar gives energy to yeast by providing food.

iii. In sugar solution, yeast can respire and as a result get multiplies.

i) The two criteria used by Mendeleev in creating his periodic table are:

a. Mendeleev arranged the elements according to their properties and in order of increasing atomic weights.

b. In the Mendeleev’s periodic table, vertical columns are called groups and horizontal rows are called periods.

ii) Mendeleev stated a periodic law. The law states that “Properties of elements are a periodic function of their atomic masses.”

i) The reflecting surface of a spherical mirror forms a part of a sphere. This sphere has a centre. This point is called the centre of curvature of the spherical mirror.

A ray is passing through the centre of curvature of a concave mirror after reflection is reflected along the same path. The light rays come back along the same path because the incident rays fall on the mirror along the normal to the reflecting surface.

Note:

ii) A ray of light from the object, parallel to the principal axis, after refraction from a convex lens, passes through the principal focus on the other side of the lens.

Biogas: In the anaerobic condition (absence of oxygen), the decomposition of waste in the form of cow dung, sewage, fruits and vegetable peels takes place. As a result, the formation of biogas takes place. The main constituent of biogas is methane. Biogas is made from:

i. First, to form a slurry, cow dung is aggregated with equal volumes of water.

ii. Then the formed slurry is decomposed by the microorganisms present in the form of waste.

iii. Then after decomposition, biogas is produced.

The two advantages of using the biogas are:

i. It has high calorific value.

ii. It is eco-friendly hence more preferable.

When an aqueous solution of HCl was taken in the beaker, and the circuit was closed, the bulb in the circuit began to glow, but it did not glow when the experiment was repeated with glucose solution because:

HCl is an acid which gets ionized into H⁺ and Cl^- ions. As we all know ions are the main responsible for the conduction of electricity. As a result, the circuit becomes complete, and bulb starts to glow.

On the other hand, glucose is not and acid. It does not get ionized because it is a carbohydrate and a covalent compound. As we know covalent compounds do not conduct electricity due to the absence of ions in them. Therefore, the bulb does not glow.

i) In the presence of NaOH, yes the bulb will glow because NaOH being a strong base gets ionized into Na⁺ and OH^- ions. These ions are responsible for the conduction of electricity. As a result, the bulb will start to glow.

ii) In the presence of NaCl, yes the bulb will glow because NaCl being a common salt gets ionized into Na⁺ and Cl^- ions. These ions are responsible for the conduction of electricity. As a result, the bulb will start to glow.

When 2 g of ferrous sulphate crystals were heated in a hard glass test tube, the following observations take place:

i) Hydrated ferrous sulphate crystals are light green in colour. They contain two water molecules. The chemical formula is FeSO₄.2H₂O. Ferrous sulphate crystals (FeSO₄.7H₂O) lose water when heated and the colour of the crystals changes. It then decomposes to ferric oxide (Fe₂O₃), sulphur dioxide (SO₂) and sulphur trioxide (SO₃). Ferric oxide is solid, while SO₂ and SO₃ are gases.

Thus, the colour changes from light green to brown.

ii) The liquid droplets on the cooler parts of the test tube are of water.

iii) Rotten type of odour is observed on heating ferrous sulphate crystals. This is due to the release of sulphur dioxide gas.

iv) When ferrous sulphate crystals are heated, give ferric oxide, sulphur dioxide and sulphur dioxide gas. The chemical reaction is given as:

2FeSO₄→ Fe₂O₃ + SO₂ + SO₃

v) In the reaction, we observe that a single reactant breaks down to give simpler products. This is a decomposition reaction.

i) No fixed position can be given to hydrogen in the Periodic Table. This was the first limitation of Mendeleev’s Periodic Table. He could not assign a correct position to hydrogen in his table because:

a. Hydrogen has 1 valence electron (electron in the outermost shell)

b. This means hydrogen belongs to halogen family I which every element has 1 electron in the outermost shell.

c. But hydrogen does not have the properties of the halogen family.

d. Sometimes hydrogen also behaves as alkali metals.

e. Due to so much confusion, no fixed position can be given to hydrogen.

ii) a. Atomic radius goes on decreasing while going from left to right in a period because of the following reasons:

i. Within a period, the atomic number increases one by one as a result nuclear charge increases.

ii. The outer electrons are adding in the same valence shell.

iii. Due to the increased nuclear charge, the attraction of electrons by the nucleus increases.

iv. Therefore, the size of the atom decreases with the increase in atomic number (number of protons).

b. Atomic radius goes on increasing down a group because:

i. Down a group, the atomic number increases one by one as a result nuclear charge increases.

ii. The outer electrons are adding in a new valence shell.

iii. Therefore, the distance between the outermost electron (valence electron) and the nucleus is also increasing

iv. Therefore, the size of the atom increases with increase in atomic number.

OR

i) Mendeleev left some gaps in his Periodic Table. Instead of looking upon these gaps as defects, Mendeleev boldly predicted the existence of some elements that had not been discovered at that time. Mendeleev named them by prefixing a Sanskrit numeral.

ii) In periodic table, the electronic configuration of elements while moving from left to right in a period increases but the number of shells remain same.

Human alimentary canal: The alimentary canal is a long tube extending from the mouth to the anus.

Oesophagus: From the mouth, the food is taken to the stomach through the food-pipe or oesophagus.

Gall bladder: It is located at below the liver. It stores the bile juice.

Pancreas: The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

Liver: It is very large gland and placed in the upper right side in the abdomen. It produces bile juice which is needed for the emulsification of fats.

OR

Excretory system: The excretory system includes the process of excretion. The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion.

The excretory system of human beings includes a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.

Aorta: It delivers the blood to the kidneys. Then this blood is filtered by the kidneys.

Vena Cava: It carries the deoxygenated blood.

Urinary bladder: It collects the waste excreted by the kidneys.

Urethra: It acts as the path between the urinary bladder and the external part of the body.

i) a. Implantation: The fertilised egg (zygote) starts dividing and form a ball of cells or embryo. The embryo is implanted in the lining of the uterus where they continue to grow and develop organs to become foetus. Hence the uterus prepares itself every month to receive and nurture the growing embryo. The lining thickens and is richly supplied with blood to nourish the growing embryo. This whole process is called implantation.

b) Placenta: The embryo or child in the womb gets nutrition from the mother’s blood with the help of a special tissue called placenta. This is a disc which is embedded in the uterine wall. It contains villi on the embryo’s side of the tissue. This provides a large surface area for glucose and oxygen to pass from the mother to the embryo. The developing embryo will also generate waste substances which can be removed by transferring them into the mother’s blood through the placenta.

ii) The sexual act always has the potential to lead to pregnancy. The average duration of human pregnancy is approximately about nine months.

Analogous organs: Analogous organs are the organs which have different structures but have similar functions.

For example Wings of an insect and wings of a bat

Homologous organs: Homologous organs are the organs which have different functions but have similar structures.

For example: Forelimbs of frog and forelimbs of human

The traits acquired by an individual during the lifetime are not inherited because an acquired trait involves a change in the non-reproductive tissue. These traits do not bring any change to the DNA. For example, a way of speaking, swimming, playing

Given: Lens is convex

Distance of the object from the lens (u) = -12cm

Focal length (f) = 8cm

Position of the image =?

To calculate position of the image, apply the lens formula:

•

•

•

•

• v = 24cm

Thus, the position of the image is 24cm.

A negative sign in the value of the magnification indicates that the image is real. A positive sign in the value of the magnification indicates that the image is virtual. Hence, to find the nature of the image, we will calculate magnification:

•

• m = -2

Thus, the nature of the image is real because magnification shows a negative value.

OR

Magnification: Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size.

It is usually represented by the letter (m). It is expressed as the ratio of the height of the image to the height of the object. The formula for magnification is given as:

Given: v = -40cm

u = -20cm

To calculate the focal length of the mirror, apply the formula:

•

•

•

•

Thus, the focal length of the mirror is -40/3.

When in an electrical circuit, a conductor of electricity induces a lot of currently more than its capability, then it is said that overloading of an electrical circuit has been taking place.

The two possible causes due to which overloading of an electrical circuit takes place are:

i. When a number of appliances are connected to a single socket, this causes overloading and can cause heating too.

ii. Overloading occurs when live and neutral wires come in direct contact with each other. This causes a short circuit too.

The two precautions that should be taken to avoid the overloading of the domestic electric circuit is:

i. To use thick wires instead of thin wires because thin wires cannot bear a current with overloading. On the other hand, thick wires have the capacity to bear current.

ii. Avoid connecting of number of appliances in the same socket.

Given: R₁ = 5Ω

R₂ = 10Ω

EMF = 6V

i) To obtain minimum current, we should connect the two resistors in series. To obtain maximum current, we should connect the two resistors in parallel.

ii) Calculation of strength of the total current in both the cases:

I case: Resistors in series

When several resistors are joined in series, then the total resistance (R_s) is equal to:

R_s = R₁ + R₂

• R_s = 5Ω + 10Ω = 15Ω

To calculate the flowing current (I), apply the Ohm’s law:

V = IR

•

• I = 0.4A

Thus, by connecting the resistors in series, the minimum current flowing is 0.4A.

II case: Resistors in parallel

When several resistors are joined in series, then the total resistance (R_P) is equal to:

•

•

•

To calculate the flowing current (I), apply the Ohm’s law:

V = IR

•

• I = 1.8A

Thus, by connecting the resistors in parallel, the maximum current flowing is 1.8A.

i) The compounds which are formed by the transfer of electrons from a metal to a non-metal are known as ionic compounds. Ionic compounds are also known as electrovalent compounds.

Examples: NaCl, CaCl₂

Melting and boiling points of ionic compounds are high because to break the attraction between the ions, a large amount of energy is needed for that.

ii) Aluminum is more active than iron, yet there is less corrosion of aluminum when both are exposed to air because:

a. Being more reactive, aluminum reacts with oxygen and forms a layer of aluminum oxide.

b. This protective layer prevents the aluminum from reacting with air.

c. Hence, less corrosion takes place.

d. On the other hand, iron is not able to form such layer, hence it gets corroded easily.

iii) Alloying (mixing of metals and non-metals) is a very good method for improving the properties of the metal. By alloying, we can get the desired properties. Solder is an alloy of lead and tin. Solder has a low melting point. Because of the low melting point, a solder helps to balance a good interaction between the two points of lower resistance. Due to this property, solder is used for welding electrical wires together.

iv) It is easier to obtain metal from its oxide, as compared to its sulphides. Therefore, before reduction, the metal sulphides must be converted into metal oxides. The sulphide ores are converted into oxides by heating strongly in the presence of excess air. This process is known as roasting.

The chemical reaction that takes place during roasting of zinc ores can be shown as:

2ZnS + 3O₂ + Heat → 2ZnO + SO₂

v) Tarnished copper vessels mean copper vessels which have a coating of green carbonate which is basic. To neutralize the effect of the base, an acid is needed. Hence, tamarind juice which is acidic in nature is used to neutralize the effect of tarnished copper vessels.

i) a. Oxidation reaction:

Carbon compounds can be easily oxidised on combustion. This is called an oxidation reaction. A chemical equation for a reaction in which alcohol (ethanol) is converted to carboxylic acid (acetic acid):

b. Addition reaction:

When unsaturated hydrocarbons add hydrogen in the presence of catalyses such as palladium or nickel to give saturated hydrocarbons. This process is called an addition reaction.

Industrial application: The above reaction is used in the hydrogenation of vegetable oils using a nickel catalyst. Vegetable oils generally have long unsaturated carbon chains.

c) Substitution reaction:

A reaction in which one type of atom or a group of atoms takes the place of another. Example: In the presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one. The chemical reaction is given as:

CH₄ + Cl₂→ CH₃Cl + HCl (in the presence of sunlight)

ii) Ethanol is an organic compound. It is a liquid at room temperature. Ethanol is commonly called alcohol. It is also used in medicines such as tincture iodine, cough syrups, and many tonics. Ethanol is also soluble in water in all proportions. Consumption of small quantities of dilute ethanol causes drunkenness.

When ethanol is heated at 443K with an excess of concentrated sulphuric acid, it gives an unsaturated hydrocarbon. The ethanol gets dehydrated to form ethane. The reaction is given as:

CH₃—CH₂OH + Hot conc. H₂SO₄→ CH₂=CH₂

EthanolEthene

The concentrated sulphuric acid can be regarded as a dehydrating agent which removes water from ethanol.

When the movement in plants is growth dependent then it is called tropic movement. It is a directional movement in response to stimulus. For example:

Phototropism- Movement towards the direction of light. Example: Movement of shoot of plant upwards towards light.

Auxin hormone is synthesized at the shoot tip. Plant shoot bend towards light during its growth because plant hormone named auxin is present at the tip of shoot.

It is a growth promoting hormone.

• The primary function of the auxin hormones is to elongate plant cells in the stem. Auxin by some mechanism breaks the bonds holding its cellulose fibers together. These broken bonds give the cell wall greater flexibility and expandability, so that more water can enter the cell by diffusion, causing the cell itself to elongate.

• Auxins are also responsible for adventitious root development, secondary growth in the vascular cambium,

• Inhibition of lateral branching, and fruit development. In fact, seedless fruits can be artificially created by applying synthetic auxin to plants; this causes fruit to develop even though fertilization (and thus seed formation) has not occurred.

It can be explained by help of this diagram. This kind of movement is induced by light. The stem mostly grows and turns towards the source of light, therefore it is said to be positively phototropic. Auxin distribution controls phototropism.

In 1, Sunlight strikes the plant from directly above. Auxin (pink dots) encourages growth straight up. In 2, 3, 4, Sunlight strikes the plant at an angle. Auxin is concentrated on one side, encouraging growth at an angle from the preceding stem. More growth of the stem on the shaded side is due to more accumulation of auxin on the shaded side than on the illuminated side.

This unequal distribution of auxins on the two sides may be due to following two reasons:

• Translocation of auxins from illuminated side to the shaded side.

Inhibition of auxin synthesis in the illuminated side (light side).

iii. The pathway of the reflex action is called Reflex arc. Reflex action is any spontaneous, involuntary and automatic response to a stimulus to protect us from harmful situations. For e.g. when a person touches a hot plate a sudden action leading to withdrawal of hand occurs in a certain manner, this path of manner determines the reflex arc.

The entire process of response to a peripheral nervous stimulation that occurs involuntarily is called a reflex action. It is defined as an inborn, involuntary mechanical response to stimuli. The reflex pathway comprises at least one afferent neuron and one efferent neuron appropriately arranged in a series. The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS. The efferent neuron then carries signals from CNS to the effector.

The sequences of events occurring when we step on a sharp object are:

• Nerve endings located in the leg identifies the irritant entered in the foot.

• Receptor sends the information or nerve impulse to the sensing (recognition) centre located in the brain stem.

• Brain stem sends instructions to the leg muscles for response.

• The muscle cells move by contraction and relaxation by utilizing the energy in the form of ATP. Muscle contraction is initiated by signals sent by the CNS to the muscle fibres. During contraction, the muscles fibres shorten, the muscle pulls on the ligaments that connect the bones and the movable body parts.

• Leg is moved apart from the sharp zone.

During relaxation the muscle fibres come to their original position. This movement of muscles cells or the muscle fibres results in the movement of the body parts.

The biggest difference between the two is that the nervous system uses electrical impulses to send signals through neurones, whereas the hormonal system uses chemical messengers transported into blood plasma to target cells. Transmission by the nervous system is short-lived but quick, whereas transmission by the hormonal system is long-lasting but takes much longer. This means that communication is faster when using the nervous system. In the nervous system, responses are localised - whereas in the hormonal system, they are widespread. Responses are often permanent in the hormonal system, but temporary and reversible in the nervous system.

• Nervous system is made of neurons whereas endocrine system is made of secretory cells called glands.

• In nervous system, the messages are transmitted in the form of electrical impulses whereas in endocrine system, the messages are transmitted in the form of chemicals called hormones.

OR

Human Brain: It is enclosed in cranium (brain box) and is protected by cerebrospinal fluid which acts as a shock absorber. Human brain has three major parts or regions: (a) Fore-brain (b) Mid Brain (c) Hind Brain.

They also have components:

âFore-brain

It is the most complex/specialized part of the brain.

(A)Cerebrum-

(i) Main thinking and largest part of the brain.

(ii) It has 3 main areas:

a) Sensory area- to receive impulses from sense organs via Receptors

b) Motor area- control voluntary movements.

c) Association areas- Reasoning, learning & intelligence.

(B) Thalamus – It relays sensory information to the Cerebrum.

(C)Hypothalamus- It forms the link between Nervous system & Endocrine system.

â Mid brain- It connects the fore-brain with the hind-brain. It is the portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation.

â Hind brain- Connects the Fore brain & Hind brain

a) Cerebellum – Controls & coordinates muscular movements, maintaining body posture and equilibrium.

b) Pons- Acts as a bridge between brain & spinal cord

c) Medulla oblongata- Controls involuntary actions like blood pressure, salivation, vomiting, etc.

Functionof cerebellum:

The cerebellum receives information from the sensory systems, the spinal cord, and other parts of the brain and then regulates motor movements. The cerebellum coordinates voluntary movements such as posture, balance, coordination, and speech, resulting in smooth and balanced muscular activity.

In case of damage to the cerebellum, while not causing paralysis or intellectual impairment, might lead to a lack of balance, slower movements, and tremors (shaking). Complex physical tasks would become unsteady and halting.

i. (a) Magnetic field is a quantity that has both direction and magnitude.

(b) The direction of the magnetic field is taken to be the direction in which a north pole of the compass needle moves inside it.

(c) Therefore, it is taken by convention that the field lines emerge from north pole and merge at the south pole (note the arrows marked on the field lines in the diagram). Inside the magnet, the direction of field lines is from its south pole to its north pole.

(d) Thus, the magnetic field lines are closed curves. The relative strength of the magnetic field is shown by the degree of closeness of the field lines. The field is stronger, that is, the force acting on the pole of another magnet placed is greater where the field lines are crowded (see diagram). No two field-lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.

(ii) Right Hand Thumb Rule

A convenient way of finding the direction of magnetic field associated with a current-carrying conductor is given in the diagram. Imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field, as shown in the diagram. This is known as the right-hand thumb rule.

OR PART

i. A coil of many circular turns of insulated copper wire

wrapped closely in the shape of a cylinder is called a solenoid. The pattern of the magnetic field lines around a current-carrying solenoid is shown in the diagram. One end of the solenoid behaves as a magnetic north pole, while the other behaves as the south pole. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.

ii.

The direction of the magnetic field as per the right-hand thumb rule is shown on the plane in the diagram. The direction is outwards the plane of the paper in the inner part of the loop and is directed inside the plane of the paper in the outer region of the loop.

It is given that a person is unable to see distinctly the words printed on a newspaper. This means person is not able to see the nearby objects clearly. The defect of vision the person is suffering from is hypermetropia.

i. This defect is also called as far-sightedness.

ii. A person with hypermetropia can see distant objects clearly but cannot see nearby objects distinctly.

iii. This is because the light rays from a close by object are focussed at a point behind the retina.

The possible causes of hypermetropia are:

i. The focal length of the eye lens is too long.

ii. The eyeball has become too small.

This defect can be correctedby using a convex lens of appropriate power. This is shown in the figure below:

i) Sustainable development: Sustainable development is a development which does not cause overuse of resources and fulfilling the needs of the present, but without cooperating with the ability of future generations to meet their own requirements and at the same time replacing the existing resources.

It is necessary because:

a. It increases economic growth. Conservation of resources rises the economic activities.

b. It enhances the quality of life by increasing the span of life.

c. Due to the development which are causing problems for human beings and our future generation too. Hence, sustainable development is necessary.

d. The concept of sustainable development encourages forms of growth that meet current basic human needs.

ii) Water harvesting: In water harvesting, the aim is to develop primary resources of land and water, to produce secondary resources of plants and animals for use in a manner which will not cause ecological imbalance. Water harvesting is an age-old concept in India.

The four benefits of water harvesting are:

i. Water harvesting increases the production and income of the watershed community.

ii. It moderates droughts and floods and increases the life of the downstream dam and reservoirs.

iii. It does not evaporate, but spreads out to recharge wells and provides moisture for vegetation over a wide area.

iv. The groundwater is also relatively protected from contamination by human and animal waste.

Less is the pH of a solution; more the solution is acidic in nature.

More is the pH of a solution; more the solution is basic in nature.

i) Among the solutions:

A = 3

B = 7

C = 12

D = 8

A is more acidic because its pH value is very less. On the other hand, C is more basic because its pH value is high.

ii) As the acidic nature increases, the concentration of hydrogen ions also increases. As the basic nature increases, the concentration of hydrogen ions decreases.

Hence the order of the given solutions in the decreasing order of their hydrogen ion concentration is given as:

A < B < D < C

When we add sodium bicarbonate to acetic acid, this produces sodium acetate, water and carbon dioxide gas is also released during the reaction. The chemical reaction is given as:

NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂

The presence of the carbon dioxide can be tested through passing limewater through it. If we pass the carbon dioxide gas through limewater [Ca(OH)₂], the whole limewater changes to a milky appearance. The reaction is given as:

Ca(OH)₂ + CO₂→ CaCO₃ + H₂O

While doing the experiment to show light is necessary for photosynthesis, the correct suggestion given by the students are:

i. The leaf should be boiled in alcohol with water bath to remove chlorophyll because alcohol is inflammable

ii. Transparent paper strip should be used instead of black paper strip.

iii. The plant should be destarched before starting the experiment.

i. The correct set-up for the experiment is as shown in the diagram. The points E, F mark the position of the allpins.

ii.

The justification is that the pins should be around 5- 10 cm. apart and the incident angles chosen should be common values so as to make the calculations easy.

By knowing the resistance of each bulb, we can know that which bulb will glow brighter. Higher the resistance, brighter the bulb will glow.

I case: Bulb A(60 W, 220V)

Given: Power = 60W

Voltage = 220V

To calculate the resistance by the formula V = IR, first, we need to find out the current flowing in the bulb. Apply the formula:

P = VI

•

• I = 0.27A

Now apply the formula:

V = IR

•

• R = 814.8 ohm

Thus, the resistance of the bulb A is 814.8 ohm.

II case: Bulb B(100 W, 220V)

Given: Power = 100W

Voltage = 220V

To calculate the resistance by the formula V = IR, first, we need to find out the current flowing in the bulb. Apply the formula:

P = VI

•

• I = 0.45A

Now apply the formula:

V = IR

•

• R = 488.8 ohm

Thus, the resistance of the bulb B is 488.8 ohm.

The resistance of the bulb A is higher. Hence it will glow more brighter than bulb B.

OR

It is given that in a voltmeter there are 20 divisions between the 0 mark and 0.5 V mark.

Given: Number of divisions = 20

Distance between the two marks = 0.5V – 0V = 0.5V

We need to find out the least count of a voltmeter.

Least count: The smallest measured value of any instrument is said to be the least count of that instrument. It is measured as:

• Least count of voltmeter = 0.025V

Thus, the least count of the given voltmeter is 0.025V.

This is possible because young stamens are not sexually mature.

Explanation: Stamens produce pollen grains only when they are sexually mature, i.e., older. Therefore dispersal, pollination, and fertilization don’t occur to produce the fruit.

Root hair

Explanation: Root hairs are minute hair-like structures on the roots of plants. They help in respiration and absorption of water and minerals from the soil. As we know the soil is full of air spaces. The root hairs are a means for this air to enter into the root through its thin cell walls. The carbon dioxide produced as a by-product also diffuses out from the root hairs. Hence exchange of gases happens successfully.

i. Na and K -Alkaline Metals

F and Cl- Halogens

Explanation: Na and K of group 1 are called alkaline metals and share the same properties. They are highly metallic and have large atomic sizes.

F and Cl are halogens of group 7. They are all gases and are highly electronegative with small atomic sizes.

ii. The given sequence represents the periodic law.

Explanation: According to the periodic law, the elements are arranged according to the increasing order of atomic masses. Since in the given sequence elements are arranged according to that we can apply this law here.

The data given is:

the object distance is, u = -30 cm.,

the focal length is, f = -15 cm,

we know that the mirror formula is,

, where,

v is the image distance, u is the object distance, and f is the focal length of the mirror, here as the mirror is concave, so the focal length is negative (-30 cm).

Calculations:

So, after substituting the data we have,

So, we get v = -30 cm.

Finally, by looking at the ray diagram we observe that the image is real as the image distance is found to be negative, also the image is inverted and is formed on the sample where is object is kept.

• Hydroelectric power plants are special power plants designed to convert the potential energy of falling water into electricity.

• In these plants, dams are constructed on heights on the river to stop the flow of water.

• This helps in the collection of water in larger reservoirs.

• As the water level rises the kinetic energy of flowing water gets transformed into potential energy (stored at a height).

• The water from the high level in the dam is carried through pipes, to turbines present at the bottom of the dam.

• This rotates the turbines and this in turn products electricity.

Limitations:

• These kinds of dams cannot be constructed everywhere and can be constructed only in hilly areas.

• Large areas of human habitation and agricultural lands are destroyed in the process.

• Large scale deforestation occurs.

• Large eco-systems are destroyed when submerged under the water in dams.

• The trees which get submerged inside the water rot under anaerobic conditions and give rise to large amounts of methane which is a green-house gas.

i. Pb₃O₄is the oxidising agent as it loses its oxygen to oxidize HCl.

ii. O₂ acts as the oxidizing agent here as it oxidizes Mg to form MgO.

iii. CuSO₄ is the oxidizing agent here as it loses its oxygen here and oxidizes Zn to form ZnSO₄.

iv. V₂O₅ is the oxidizing agent here as it loses its oxygen to Ca to oxidize it into CaO.

v. H₂O is the oxidizing agent here as it loses its O₂ to oxidize Fe into Fe₃O_4.

vi. CuO is the oxidizing agent here as it loses oxygen and oxidizes H₂ to H₂0.

i. a. blue (due to the water of crystallisation)

b. white (due to the loss of water of crystallisation after heating)

ii. 1 M HCl has a higher concentration of H⁺ ions as HCl is a stronger acid compared to CH₃COOH.

(Reason: A strong acid produces more H⁺ ions on ionisation than a weak acid. Here HCl is a strong acid compared to CH₃COOH).

i. X is placed in the third period and 17^th group. (This is due to the electronic configuration of the element which is 2,8,7)

Y is placed in the third period and 2^nd group (This is due to its electronic configuration-2,8,8,2)

Important: The number of shells gives the period in which the element is placed.

The outer electronic configuration of the elements determines the group in which it is placed. Elements with 7 valence electrons will fall into the 17^th group and 2 valence electrons will fall into the 2^nd group).

ii. X is a non-metal and Y is a metal.

Important: X is a non-metal as it is present in the right-hand side of the periodic table (metallic character is the lowest here). Similarly, Y is a metal as it is present on the left-hand side of the periodic table. (metallic character is the highest here).

iii. The oxide of Y will be acidic. The nature of bonding will be ionic.

(Reason: Oxides of metals are acidic and ionic in nature and oxides of non-metals are basic and covalent in nature)

iv.

The divalent halide formed is YX₂.

i. B forms only covalent compounds. (Reason: B has a very small size)

ii. Doesn’t exist

iii. B is a non-metal with valency 3 (reason: It has seven valence electrons)

iv. Noble gases (Reason: They are inert as they are very stable)

v. D has a bigger atomic radius as atomic radius decreases across a period.

• Leaves contain chloroplasts which store chlorophyll which is a necessary pigment for photosynthesis.

(reason: Chloroplasts are a kind of cell organelle which store the pigment chlorophyll which helps in photosynthesis. Photosynthesis doesn’t take place without this pigment.)

• Leaves also contain stomata which are pores which help in gaseous exchange of carbon dioxide and oxygen.

(reason: Stomata are pores on the leaves which are minute openings guarded by bean shaped cells called guard cells. The opening and the closing of stomata lets in and gives out oxygen and carbon dioxide which is highly necessary for photosynthesis to take place.)

• Leaves also have an elaborate network of veins for circulation and distribution of food and water.

(reason: Veins are tubular pathways for the movement of food materials, water and minerals in and around a leaf. Therefore, it can be clearly said that the venation in leaves makes it fit for photosynthesis to take place).

The process of asexual reproduction in which the vegetative parts of a plant are used for reproduction is called vegetative propagation. (Asexual reproduction is a kind of reproduction which takes place without the fusion of gametes and doesn’t require the presence of both the sexes)

Advantages

• Plants raised by vegetative propagation bear flowers and fruits earlier than those produced from seeds.

(Reason: Since the elaborate processes of pollination, fertilization and the development of the fruit doesn’t have to take place the reproduction is much faster)

• The plants produced are genetically similar to the parent plant.

(Reason: Since there is no fusion of gametes or genetic material, genetic recombination does not take place (genes do not mix :0) and offspring are just like their parents.

• A large number of plants can be produced.

(Reason: As said above, this process is much faster and in less time a lot of plants are produced)

Disadvantages

• There is no variation in the offsprings produced and the fertility of the plants is reduced.

(Reason: as said above genetic mixing doesn’t take place and the same genes are transferred again and again which leads to infertility)

OR

i. Organs having a common underlying anatomy that was present in their last common ancestors are called homologous organs. (homo : same logy : structure)

Evidences: bat's wing, wings of birds, seal’s flipper, forelimb of a horse, and human arm. They have the same bone structure with radius, ulna, carpals, metacarpals and phalanges. But they have different functions like swimming and flying.

ii. Analogous organs are the opposite of homologous organs, which have similar functions but different origins. (Ana: different logy: structure)

Evidences: wings of insects, bats and birds. All of them are used for flying but are made of different structures. Like the wings of insects are made of chitin(a polysaccharide) and the birds have their wings made of a bony skeleton. Structures are all different but the function is same-flight.

iii.Preserved traces of living organisms in rocks and soil are called fossils. They tell about the age of the animal.

Evidences: A dinosaur skull fossil was found a few years ago in the Narmada valley. This shows that dinosaurs did exist.

i.Green (Genotype will be Gg)

iii. 25%

Out of the four genotypes only one genotype gives purple

Stemmed plants therefore only 25% of the plants are

purple stemmed.

iii.The ratio of GG and Gg plants is 3:1 as shown in the figure.

Note: In the above figures, green colour depicts green stemmed plants and purple colour shows purple stemmed plants.

The data given is:

the object distance is, u = -15 cm,

the focal length is, f = -10 cm,

the height of the object, h_o = 4 cm,

we know that the mirror formula is,

, where,

v is the image distance, u is the object distance and f is the focal length of the mirror, here as the mirror is concave so the focal length is negative (-10 cm).

Calculations:

So, after substituting the data we have,

So, we get .

The screen should be placed 30 cm. in front of the concave mirror so as to obtain a sharp image of the object. The magnification can be calculated by the formula,

,

,

,

The height of the image is 8 cm. and negative sign shows that the image is real and inverted.

OR

The data given is:

the image distance is, v = -15 cm,

the focal length is, f = -20 cm,

the height of the object, h_o = 6 cm,

we know that the lens formula is,

, where,

v is the image distance, u is the object distance and f is the focal length of the lens, here as the lens is concave so the focal length is negative (-20 cm).

Calculations:

So, after substituting the data we have,

So, we get .

The object should be placed 60 cm. in front of the concave lens so as to obtain image of the object at the given position. The magnification can be calculated by the formula,

,

,

,

The height of the image is 1.5 cm. and the image is virtual and erect.

i. Given :

The current in the bulb = 10A,

The applied voltage = 220 V,

Calculations:

By Ohm’s law, we have v = iR where v is the applied voltage across the resistance R, flowing current through it is i amperes.

Substituting the values, we get

220 = 10 × R,

R = 22 Ω

So, the resistance of the bulb is 22 Ω

ii. The circuit diagram is,

i. Force on a current carrying conductor placed in a magnetic field

French scientist Andre Marie Ampere (1775–1836) suggested that when a current-carrying conductor is placed in a magnetic field it will experience a force. The force due to a magnetic field acting on a current-carrying conductor can be demonstrated through the following activity.

1.Take a small metal (preferable aluminium) rod AB of about 5-10 cm in length. Using two connecting wires suspend it horizontally from a stand, as shown in the diagram.

2.Place a strong horse-shoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this put the north pole of the magnet vertically below and south pole vertically above the rod.

3. Connect the rod in series with a battery, a key, and a rheostat.

4. Press the key ‘k’ to let the current flow through the rod.

Observations - It is observed that the rod is displaced towards the left. Reversing the direction of current flowing (by changing the polarity of the battery) through the rod, it is observed that the direction of its displacement of the rod is now towards the right. The displacement of the rod in the above activity suggests that a force is exerted on the current-carrying rod when it is placed in a magnetic field. It also suggests that the direction of force is also reversed when the direction of current through the conductor is reversed.

ii. Fleming’s Left-Hand Rule

Fleming’s left-hand rule states that when you stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular and if the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.

i. A- Ethanoic Acid C₂H₄O₂

(Reason: Ethanoic acid or acetic acid is a weak carboxylic acid. acids react with alkali metals, hydrogen gas is produced)

B- hydrogen

(reason: hydrogen gas is released as an acid reacts with a metal)

C-Ester CH₃COOC₂H₅

(reason: Esters are sweet smelling substances formed when carboxylic acids react with alcohols. Here ethanoic acid reacts with ethanol.

ii. a. C₂H₄O₂+Na→CH₃COONa+H₂

B. C₂H₄O+C₂H₅OHCH₃COOC₂H₅

Important: To write equations in organic chemistry easily ,you need to learn the nomenclature of organic compounds and learn the properties of all the hydrocarbons and functional groups)

iii. Detergents are ammonium or sulphonate salts of long chain carboxylic acids.

Explanation : They are advantageous over soaps as-

• Hard water has carbonates and bicarbonates of calcium and magnesium. When soaps are used, the salts in hard water combine with soap and form a scum like substance which is hard to remove and sticks to the clothes. This defeats the very purpose of washing clothes, sigh. But when detergents do not have this scum problem. Therfore they are more preferable.

OR

i. A hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.

Eg- methane, ethene etc.

ii. Saturated fats have no double bond between molecules, which means there are no gaps.But, in unsaturated compounds, there exists double bonds.

iii.An atom or group of atoms which show unique reactivity when treated with some reagents and impart unique chemical, and physical properties to the primary molecule, is defined as a functional group.

(Explanation: Functional groups are like different families and each family has different characteristics. Each family also have different names

Eg-alcohols, ketones and aldehydes.

i. The molecules of air and other fine particles in the atmosphere have a size smaller than the wavelength of visible light. These are more effective in scattering light of shorter wavelengths at the blue end than the light of longer wavelengths at the red end.

ii. The red light has a wavelength about twice that of blue light. Thus, when sunlight passes through the atmosphere, the fine particles in the air scatter the blue color (shorter wavelengths) more strongly than red.

iii. The scattered blue light enters our eyes. Light from the Sun near the horizon passes through thicker layers of air and larger distance in the earth’s atmosphere before reaching our eyes. However, light from the Sun overhead would travel a relatively shorter distance.

iv. At noon, the Sun appears white as only a little of the blue and violet colors are scattered. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance of the Sun.

The following activity illustrate the above effect: -

1. Place a strong source (S) of white light at the focus of a converging lens (L1). This lens provides a parallel beam of light.

2.

3. Allow the light beam to pass through a transparent glass tank (T) containing clear water.

4. Allow the beam of light to pass through a circular hole (c) made in a cardboard. Obtain a sharp image of the circular hole on a screen (MN) using a second converging lens (L2), as shown in the diagram.

5. Dissolve about 200 g of sodium thiosulphate (hypo) in about 2 L of clean water taken in the tank. Add about 1 to 2 mL of concentrated Sulphuric acid to the water.

Observations: -

It is observed that the microscopic Sulphur particles start precipitating in about 2 to 3 minutes. As the Sulphur particles begin to form, it is observed that the blue light from the three sides of the glass tank. This is due to scattering of short wavelengths by minute colloidal Sulphur particles. The color of the transmitted light as observed from the fourth side of the glass tank facing the circular hole at first is orange red color and then slowly changes to bright crimson red color on the screen.

i.

ii. The direct current generator or the DC dynamo is based on the principle of Faraday’s law of electromagnetic induction.

iii. The device is used to convert the mechanical energy into useful electric energy.

iv. The mechanical energy supplied from outside is used to rotate the conductor in the magnetic field to produce electricity.

v. An electric generator, as shown in the diagram, consists of a rotating rectangular coil ABCD as placed between the poles of a permanent magnet.

vi. The two ends of the coils are connected to two rings R₁ and R₂. The inner side of these rings are made insulated. The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2, respectively.

vii. The two rings R1 and R2 are internally attached to an axle. The axle is mechanically rotated from outside to rotate the coil inside the magnetic field.

viii. The mechanical energy may come from flowing water inside a hydel dam or a by high pressurized steam in a thermal power plant. Outer ends of the brushes are connected to the load. In an experimental setup it is connected to the galvanometer to detect any current in the circuit.

i. (a) To conserve biodiversity.

Explanation: The loss of diversity my lead to biological instability.

Forests also are the homes for many animals and also give us valuable forest products.

(b)We need to conserve wildlife to maintain the ecological stability.

(Explanation: The animals also provide us with various economical products and the livelihood of many people depends on the both.)

ii. *It can provide year-round supply of dinking water to the community.

(Explanation: The water harvested can be used during the drier season)

*Groundwater is protected from contamination by human and animal waste.

iii. 10000 J of energy was available to the producer.

(Explanation- Only 1/10^th of energy is passed on to the next energy level. Therefore 1/10^th of 10000 is 1000 J is available for the deer.1/10^th of 1000 is 100J is available for the lion.)

OR

i. Chlorofluorocarbons (CFCs)

(Explanations are carbon compounds which destroy the ozone layer by thinning the layer and creating ozone holes)

ii. (i) Using public transport or walking/cycling.

(ii) Using LED bulbs at homes and switching off fans and lights when not in use.

(iii) Taking the stairs instead of the elevator.

(iv) Wearing an extra sweater instead of using a heater on cold days.

(v)Not wasting paper and using less plastic.

i. This is an example of a displacement reaction. A container containing blue copper sulphate solution is taken. Amit immersed an iron rod in the copper sulphate

The iron nail becomes brownish in colour after some time.

(ii) Displacement reaction

This is an example of a displacement reaction.

Fe + CuSO₄ FeSO₄ + Cu

The Fe displaces Cu from CuSO₄ and the solution becomes CuSO₄ and is thus in green colour. The copper metal formed is deposited on the iron nail and gives a brownish colour.

Ethanoic acid or acetic acid is a carboxylic acid. When carboxylic acids are added to metal carbonates or bicarbonates, carbon dioxide gas is produced. The observations made are-

• A colourless odourless gas is produced which turns lime water milky. (Reason: as stated above, carbon dioxide gas is produced)

• Water droplets are also found in the walls of the flask. (Reason: as stated above water vapour is formed which condenses on the walls of the flask)

The reaction is as follows-

NaHCO₃ +CH₃COOH NaC₂H₃O₂ + H₂O + CO₂

Experiment to show that CO₂ is released during respiration.

• Take a conical flask and place some germinating seeds in it. Hang a test tube filled with potassium hydroxide solution (this solution absorbs carbon dioxide) inside the conical flask.

• Now take a rubber cork with a hole it. Insert the short end of a glass tube inside the conical flask.

• Take coloured water in another beaker. Now take the longer end of the glass rod and dip it in the coloured water. Note the initial water level through the glass rod.

• Leave the setup undisturbed for an hour. Notice the final water level in the glass rod.

Observations- You will observe that the water level in the glass rod has increased.

The splitting of light into its component colours is called dispersion.

The dispersion of white light by prism is as shown in the diagram

The colour of yolk of an egg is somewhat similar to the colour at the position 5 and the colour of a ladyfinger is somewhat similar to the colour at the position 6.

The experimental setup given in the diagram will not give the correct reading of voltage ‘V’, but will give the correct reading of the current ‘I’ in the circuit as voltmeter should be connected in parallel with the resistors in order to measure the drop across the resistors.

OR

The experimental setup is to evaluate the equivalent resistance of 2 resistor in series. The required instruments are a voltmeter, an ammeter and a rheostat. The ammeter is always connected in series as it measures the total current in the circuit, voltmeter in parallel as it measures the net voltage drop across the resistors and the rheostat is connected to control the current flow in the circuit. The complete diagram is given as,

The green dot-like structures in cells observed by a student when a leaf peel was viewed under the microscope were chloroplast.

Chloroplasts are very important in photosynthesis, the process by which light energy is converted to chemical energy, resulting in the production of oxygen and energy-rich organic compounds (as they convert the energy from sunlight into food).

Chloroplasts are distinguished from other types of plastids by their green colour, which results from the presence of two pigments, chlorophyll a and chlorophyll b. A function of those pigments is to absorb light energy. In plants, chloroplasts occur in all green tissues, though they are concentrated particularly in the parenchyma cells of the leaf mesophyll. The green colour in the leaf comes due to the presence of chlorophyll in chloroplasts.

Also the green colour appears to our eyes due to reflection because as sunlight falls (which is called white light and is composed of VIBGYOR) and we observe it, then all the colours get absorbed but green gets reflected back, and hence we see it as green.

In the germinating seed:

The plumule is the future shoot. It will develop to become the shoot. The plumule can be found between two cotyledons.

The radicle is the future root. It develops to become the future root.

Plumule and radicle are two parts of the plant embryo, which are found inside the seed. During the germination of the seed, radicle is developed at first through the micropyle of the seed. The radicle is the rudimentary root of the plant embryo. It grows downward into the soil, absorbing water required by the further development of the embryo. Radicle develops into the root system of the future plant. Plumule emerges secondly to the radicle from the seed. It grows upwards from the soil. Cotyledons are held by plumule. Plumule is capable of photosynthesizing, producing the food required by the growth of the embryo. It develops into the shoot of the future plant, consisting of stem and leaves. However, the main difference between plumule and radicle is in their development into different parts of the future plant.

A cotyledon is part of the embryo within the seed of a plant. Often when the seed germinates, or begins to grow, the cotyledon may become the first leaves of the seedling. The cotyledons are formed during the process of embryogenesis along with the roots and shoots of the plant prior to germination.

Functions of cotyledon:

a) Photosynthesis

The cotyledons in some cases are major photosynthetic producers during germination. As photosynthetic producers, cotyledons essentially can synthesize the organic nutrients it requires for growth through photosynthesis.

b) Leaf Growth/Food

The cotyledon encourages leaf growth in a plant's early stages of life. These leaves are important because they serve as the chief way for plants to get the nutrients they need to continue growing and thriving. When cotyledons become new green leaves, the cotyledons raise over ground level. In another process that involves plants such as peas, however, cotyledons remain underground and solely serve the function of a food source.

Cotyledons transmit the food stored in the embryo to new sprouting plants. Plants such as beans and peas -- which are dicotyldons -- have thick cotyledons that drew nutrients from the seeds prior to sprouting. Meanwhile, grass -- an example of a monocotyledonous -- has a single thin cotyledon that absorbs nutrients from the seeds as they are sprouting.

c) Reproduction

The cotyledon essentially allows a plant's embryo to begin creating new life following germination. This is a critical function because it shows that without the cotyledon, a plant essentially would not be able to breed. With the help of the cotyledon, plants can spread their seeds and boost their species' population at a rapid rate.

The Modern periodic table, developed by an English physicist Henry Mosely, is based on the the studies through X-ray diffraction, which revealed that atomic number– an indicator of the no. of protons in the nucleus, which is unique for any element – is the more fundamental criteria than atomic mass. He stated the modern periodic law as – properties of elements are a periodic function of their atomic numbers. Keeping atomic number as the base also enables us to predict how many more elements are yet to be found out in between the two known elements in the Modern periodic table. Later when noble gases were invented, they could be easily accommodated in the table.

Based on the modern periodic law, the elements are arranged into rows and columns based on their atomic number. There are 18 columns, called groups and 7 rows, called periods. We know that electrons are distributed in the various shells around the nucleus. The period represents the outermost shell to which electron is added.

The metallic and non-metallic character of elements can be largely attributed to the number of valence electrons and valence. Metallic character is characterised by the ease of elements lose electrons to attain octet. Elements having lesser than 4 electrons in valence shell are hence metallic, which means metals are found towards the left of the table.

i. As we go down a group, the valence electrons are much farther away from the nucleus, which means they can be released easier, increasing the metallic character. As for non-metals, they are found towards the right of the table; and are generally electron acceptors so as to complete their octet. Down a group, accepting an electron becomes a tougher job, decreasing non-metallic character.

ii. Similarly, as we move from left to right in a period, the metallic character and atomic size decreases as the nuclear charge increases so valence electrons are attracted with greater force.

Given, a concave lens.

Focal length, f = - 15 cm [f is - ve for a concave lens]

Image distance, v = - 10 cm [image formed is virtual i.e., on same side as the object, so v is - ve]

Now, using the lens formula,

Therefore, object distance, u = −30 cm

Ray diagram:

In order to make the diagram, let’s use a scale where 5cm = 1cm.

So, as per the new scale,

Focal length, f = -3 cm

Image distance, v = -2 cm

Steps to draw the ray diagram are mentioned below as follows:

(i) Draw a horizontal line which is called the principal axis.

(ii) Now, draw a convex lens keeping principal centre (C) on the principal axis.

(iii) Mark points F (focal length) and B (image distance) on the left side of lens at a distance of 3 cm and 2 cm respectively.

(iv)Draw a dotted line passing through F to any point on the top of the lens, say D.

(v) So, we can draw a line AD parallel to principal axis because any ray of light passing through the focal length of the lens after refraction, passes parallel to the principal axis.

(vi)Draw a line A'B', perpendicular to principal axis from B' representing the height of the image.

(vii) Draw a line CA' backwards, so that it meets the line from D at A.

(viii) Now, draw a line AB, perpendicular to the principal axis at B from point A in the downward direction.

(ix) AB is the position of object. On measuring distance BC, it will be found to be equal to 6 cm.

Thus, the object is placed at a distance of 6 cm × 5 = 30 cm from the lens (as per the original scale).

In areas where the ground is heated faster, the air rises as temperatures go up. The majority of wind power is transferred into energy by the use of turbine blades.

Wind energy is the energy harnessed from wind. The kinetic energy of wind is converted into mechanical energy. If this energy is used directly by a machine (such as grinding stone or a water pump), it is called a windmill.

If the mechanical energy is first converted into electricity, then the machine is called a wind turbine.

Limitations of Wind energy:

a) No electricity when there is any wind

The limitation of wind power is that no electricity is produced when the wind is not blowing. Thus, it cannot be used as a dependable source of base load power. Utilities and merchant generators will not invest huge sums of money into a technology that does not work when the wind is not blowing. It can be used only at those places where wind blows for the greater part of the year.

b) Wind Turbines Killing Migrating Birds

The process of turning wind into electricity is causing the death of many predatory birds whose annual migration route includes the pass. Past attempts to reduce bird kills have included painting the tips of turbine blades to try to make them more visible to birds and installing screens around generators. Still, these measures have failed to substantially lower the number of bird deaths.

c) Wind speed should be higher than 15 km/h to rotate the turbine at the required speed. This is the minimum threshold speed for wind, so that the windmills can be effective for energy production.

d) Need of a back up facility when there is no wind, as no one can control the amount and speed of wind.

e) Requires large area for setting up wind energy farms. (i.e. 1MW requires about 2 hectares of land)

f) Tower and blades require a high level of maintenance. The blades are constantly exposed to vagaries of nature like rain, sun, storm, that is why they need to be maintained for proper functioning.

i. Solid A is assumed to be MnO2 and solid B to be Aluminium (Al). When the mixture of MnO2 and Al is heated, manganese (Mn) is produced in molten state and aluminium oxide (Al2O3) floats over it. Mn is produced in the molten state as a lot of heat energy is released in the process. Therefore, “C” is Mn and “D” is Al₂O_3.

Reaction involved:

3Mn O_2(s) + 4Al_(s)→ 3Mn_(l) + 2Al₂O_3(s) + Heat

ii. The types of reaction under which the above reaction is classified are:

a. Redox reaction

Redox (reduction–oxidation reaction) is a chemical reaction in which the oxidation states of atoms are changed. Any such reaction involves both a reduction process and a complementary oxidation process, two key concepts involved with electron transfer processes.

Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.

Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

b. Displacement reaction

A displacement reaction is a type of reaction where part of one reactant is replaced by another reactant. A displacement reaction is also known as a replacement reaction or a metathesis reaction.

An example is the reaction between iron and copper sulfate to produce iron sulfate and copper:

Fe + CuSO4 → FeSO4 + Cu

Here, both iron and copper have the same valence. One metal cation takes the place of the other bonding to the sulphate anion.

i. Bleaching Powder is calcium Oxychloride. The chemical formula of bleaching powder is CaOCl2.

Bleaching powder reacts with dilute HCl to liberate Cl₂ gas, water and Calcium Chloride.

CaOCl_2(s) + 2HCl _(aq)→ CaCl_2(s) +Cl_{2 (g)} +H2O _(l)

ii. When dilute hydrochloric acid is poured on zinc granules, then zinc sulphate is formed along with the evolution of a gas. Zinc is more reactive than hydrogen, so displaced it from hydrochloric acid.

The gas evolved is hydrogen. We can test its presence by bringing a burning candle near the mouth of the test tube and hearing for a popping sound. Only hydrogen gas burns with a 'pop' sound.

2HCl _(aq) + Zn _(s)→ ZnCl_{2 (aq)} + H_{2 (g)}

iii. Mixing baking soda, or NaHCO3, with hydrochloric acid, or HCl, results in table salt, NaCl, as well as water, H2O, and carbon dioxide, CO2. These experiments can also demonstrate stoichiometry, which deals with the reactants and products in chemical reactions.”

NaHCO_3(s) + 2HCl _(aq)→ NaCl_(s) + H2O _(l) + CO2 _(g)

This is a neutralization reaction it releases bubbles of carbon dioxide gas

OR

The character of acidic, basic and neutral is defined by the concentration of hydrogen ions [H+](mol/L). A solution with a concentration of hydrogen ions higher than 10-7mol/L is acidic, and a solution with a lower concentration is alkaline.

Using the formula,

pH=-log [H+],

a pH of 7 is neutral, a pH less than 7 is acidic, and a pH greater than 7 is basic. As one can see from this formula, ten times a given concentration of hydrogen ions means one unit lower in terms of pH value (higher acidity), and vice versa.

The pH value of a solution varies from 0 to 14. The pH value is 0 for a very strong acid and the pH value is 14 for a very strong base. The pH value is 7 for a neutral solution. Hence A is acidic and B is basic in nature.

The concentration of hydrogen ion decreases from pH value of 0 to 14 therefore A has more hydrogen ion concentration.

i. and B belong to group 1 and 2 because they form basic oxides. C belongs to group 13 as it has 3 valence electrons. D belongs to group 14 as it forms almost neutral oxide. E and F belong to group 15 and 16 as they form acidic oxides, G belongs to group 17 as it has 7 valence electrons and H belongs to group 18. They belong to 3rd period of the Periodic Table because AG is NaCI, added in a small amount to almost all vegetable dishes during cooking and Na and Cl belong to 3rd period.

ii. onic compounds will be formed because ‘B’ is metal and ‘F’ is non-metal. ‘B’ can lose two electrons and ‘F’ can gain two electrons.

Ionic compounds are compounds made up of ions. These ions are atoms that gain or lose electrons, giving them a net positive or negative charge. Metals tend to lose electrons, so they become cations and have a net positive charge. Nonmetals tend to gain electrons, forming anions that have a net negative charge.

iii. A and B are definitely metals as they form basic oxides.

Metal oxides are basic in nature because they react with dilute acids to form salt and water. They also dissolve in water to form metal hydroxides which are alkaline in nature. These metal hydroxides release OH- ions, so they are basic.

iv. Elements G and H are gaseous at room temperature

v. CG³ is the formula of the compound formed by combination of C and G.

C has the valence electrons of 3 therefore its valency will be 3

G has valence electrons as 7 therefore its valency will be 1

Formula

i. Photosynthesis is an enzymatic process.

At Low Temperature

Enzymes are protein molecules used by living organisms to carry out biochemical reactions. The proteins are folded into a very particular shape, and this allows them to bind efficiently to the molecules of interest. At low temperatures, between 32 and 50 degrees Fahrenheit – 0 and 10 degrees Celsius – the enzymes that carry out photosynthesis do not work efficiently, and this decreases the photosynthetic rate. This leads to a decrease in glucose production and will result in stunted growth.

At High Temperatures

At temperatures above 68 degrees Fahrenheit, or 20 degrees Celsius, the rate of photosynthesis decreases because the enzymes do not work as efficiently at this temperature. This is despite the increase of carbon dioxide diffusion into leaves. At a temperature above 104 degrees Fahrenheit – 40 degrees Celsius – the enzymes that carry out photosynthesis lose their shape and functionality, and the photosynthetic rate declines rapidly. The graph of photosynthetic rate versus temperature presents a curved appearance with the peak rate occurring close to room temperature.

ii. Chlorophyll is the pigment used in the process of photosynthesis for light absorption. Green light is least useful in photosynthesis, because chlorophyll does not absorb green light. The light harvesting complexes mostly absorbs blue and red light to carry out photosynthesis.

Also the green colour appears to our eyes due to reflection because as sunlight falls (which is called white light and is composed of VIBGYOR) and we observe it, then all the colours get absorbed but green gets reflected back, and hence we see it as green.

OR

The small intestine is the part of the gastrointestinal tract (also called the 'digestive tract' and the alimentary canal) located after the stomach and before the large intestine. It is the part of the digestive tract where approx 90% of the digestion and absorption of food occurs, the other 10% taking place in the stomach and large intestine.

That is, absorption of the nutrients and minerals in the food ingested, usually via the mouth, at an earlier stage in the digestive process.

Digestion in the Small Intestine

Digestion is the process by which ingested (food) material is broken down into a form that can then be absorbed, then assimilated into the tissues of the body.

It is one of the main stages in the digestive process and takes two forms:

• Mechanical digestion (e.g. chewing, grinding, churning, mixing), and

• Chemical digestion (e.g. action of digestive enzymes, bile, acids, etc.).

Chemical digestion occurs in the small intestine (and, to a lesser extent, also in some other part of the gastrointestinal tract - incl. the action of saliva on food in the mouth and the actions of some chemicals secreted by cells located in the lining of the stomach).

The three main categories of nutrients that undergo digestion within the small intestine are proteins, lipids (fats) and carbohydrates.

Absorption in the Small Intestine

In order for digested material to be absorbed into the bloodstream it must first be broken-down into particles that are small enough to pass, or "be transported", across the epithelial cells of the gastrointestinal tract.

Absorption is the uptake of fluids or other substances by the tissues of the body.

Digested material is absorbed into the bodily fluids (blood and lymph). Most of the absorption part of the digestive process occurs in the jejunum and the ileum of the small intestine, though alcohol is readily absorbed through the stomach.

Assimilation is the process by which broken-down parts, e.g. the chemical components of, or derived from, ingested food and beverages are taken into the cells of the body.

Digested material may be transported into blood vessels in the wall of the small intestine by the processes of simple/passive diffusion, facilitated diffusion, primary active transport, or secondary active transport.

The structure of the small intestine is suited to these processes of absorption due to its very large surface area. That is best explained using a diagram of the anatomy of the small intestine. Briefly, the inside surfaces of small intestine have many folds called plicae circulares, from which project many tiny finger-like structures of tissue called villi. The individual epithelial cells also have finger-like projections, which are called known as microvilli.

The function of the 3 structures, (1) the plicae circulares, (2) the villi and (3) the microvilli is to: Increase the surface area available for the absorption of nutrients.

Vegetative propagation is a form if asexual reproduction in plants. Vegetative propagation is also known as vegetative reproduction, it is a process in which new plants are produced without the production of seeds or spores.

Most of the plants have the ability to reproduce sexually, there are also many plants which have the ability for vegetative reproduction or they can undergo vegetative propagation if small plant pieces are subjected to chemical treatments.

Vegetative propagation is process to increase the number of plants of a particular species. Propagation can be done by asexual methods by using the vegetative plant parts. Vegetative propagation allows plants to be created in such a way unlike the natural way. Vegetative propagation uses vegetative parts of plants to produce new plants like stems, leaves and roots. Naturally many plants can reproduce this way and it can be artificially induced.

The advantages and disadvantages of vegetative propagation are:

Advantages of Vegetative Propagation

• The main advantage of vegetative propagation is that the progeny plants contain the genetic material of only one parent.

• Clones of the parent plant are only produced.

• For example, if we have a plant of desirable traits, the same plant can be reproduced by vegetative propagation if the growing propagation remains similar.

• This technique is useful for commercial growers who want to produce only the plants with highest quality.

• Vegetative propagation can ensure the consistency of a plant variety or crop variety for sale.

• This process also helps to maintain consistent quality and taste of the products made from the plants or crops.

• For example, some tea plants like the Zealong's tea plantations, the new tea plants are made from the cutting using the older plants to ensure uniform consistency in the taste and quality of the tea.

• Vegetative propagation can save a lot of time and money for production of plants on a commercial scale.

• For example, for a tea plant to grow big enough from a cutting it takes 3-4 years to be ready for harvest and processing. Growing of the same plant from seed would take even longer.

Disadvantages of Vegetative Propagation

• Vegetative propagation has a potential impact on the biodiversity of a species.

• If a clone of a plant is susceptible to a certain disease, it is possible that the entire crops of the clone are susceptible to the same disease.

• Due to lack of genetic variation the plants may gradually lose their vigour.

• Plants are more prone to diseases that are specific to a certain species. This can cause destruction to the entire crop.

When Mendel crossed pure tall (TT) pea plants with a pure dwarf (tt) pea plants, in the F1 generation he found that all pea plants were tall (Tt). There were no dwarf plants produced in an F1 generation. When he self-pollinated these Fl plants, in the F2 generation he obtained tall and dwarf plants in the ratio 3:1.

Thus as three-fourths of the plant in an F2 generation are tall and one-fourth is dwarf so tall is a dominant trait whereas dwarf is a recessive trait which expressed itself only in homozygous condition. The dwarf trait was inherited in an F1 generation but it does not get expressed, it remains suppressed in presence of dominant trait tall.

Reappearance of the dwarf pea plants in F2 generation proves that the dwarf trait was inherited but not expressed in F1 generation.

A character is expresses depending upon whether it is dominant or recessive. A trait which is inherited, if it is a dominant character, then it will be expressed. While a trait which is a recessive character will not be expressed.

Every species or organisms has inbuilt tendency for genetic variation which plays an important role in the origin of new species and forms the basis for evolution. Organisms appear to be same because of similarity in their inherited body designs. The more characteristics two species have in common, the more closely they are related. And they are likely to have a a common ancestor more recently. Classification of organisms necessarily involves, organizing them in different groups, based on the similarities and differences of characteristics. Classifying organisms helps us in recognizing the basic arrangement of a hierarchical structure among diverse species. It tells us about the resemblances and relationships between various organisms thus facilitating studies or research of wide variety associated with organisms effortlessly.

Different life forms have evolved during the course of evolution.

Classification deals with the grouping of these life forms into groups and sub groups based on similarities and differences.

The more characteristics any two species have in common, more closely they are related.

In fact, classification of species is a reflection of their evolutionary relationship. Thus, we can say, the areas of study evolution and classification interlinked.

We are given that,

f = 18 cm, v = 24 cm, u =? m =?

Using the lens formula and substituting the values in it,

Magnification, determines the ratio of the size of the image formed by refraction from the lens to the size of the object.

v= Image distance

u= Object distance

Negative sign indicates that the image is real and inverted.

(i) Resistors are in parallel when each resistor is connected directly to the voltage source by connecting wires having negligible resistance. Each resistor thus has the full voltage of the source applied to it.

Resistors are in series whenever the flow of charge, called the current, must flow through devices sequentially.

Since, R_a is connected to the positive terminal and R_b is connected to the negative terminal, Hence they are in series.

Therefore, total resistance,

(ii)

Major Features of Resistors in Series

1. Series resistances add: R_A= R₁+ R₂+R₃

2. The same current flows through each resistor in series.

3. Individual resistors in series do not get the total source voltage, but divide it.

Major Features of Resistors in Parallel

1. Parallel resistance is smaller than any individual resistance in the combination.

2. Each resistor in parallel has the same full voltage of the source applied to it. (Power distribution systems most often use parallel connections to supply the myriad devices served with the same voltage and to allow them to operate independently.)

3. Parallel resistors do not each get the total current; they divide it.

(i) Maxwell’s Right Hand Thumb Rule:
The- direction of the magnetic field produced by a current-carrying conductor is given by Maxwell’s right hand thumb rule.

It states that if you holding the current-carrying conductor in your right hand such that the thumb points in direction of the current, then the direction in which the fingers encircle, gives the direction of magnetic lines. This rule is also called Maxwell’s Corkscrew Rule.
This rule can also be stated as if we consider ourselves driving a corkscrew in the direction of the current, then the direction in which we rotate the screw is the direction of the magnetic field.

(ii) Fleming’s Left Hand Rule:
The direction of force which acts on the current-carrying conductor placed in a magnetic field is given by Fleming’s left hand rule.

It states that if the forefinger, thumb and middle finger of left hand are stretched mutually perpendicular and the forefinger points along the direction of external magnetic field, middle finger indicates the direction of current, then thumb points along the direction of force acting on the conductor.

(iii) Fleming’s Right Hand Rule:
The direction of induced current in a straight conductor is given by Fleming’s right hand rule.
It states that if we stretch the thumb, forefinger and the middle finger of right hand at right angles to one another in such a way that the forefinger points in the direction of magnetic field.

Then, thumb gives the direction of motion of conductor (force), forefinger indicates direction of magnetic field and the middle finger points the direction of induced current.

OR

A fuse is nothing more than a short length of wire designed to melt and separate in the event of excessive current. Fuses are always connected in series with the component(s) to be protected from over current, so that when the fuse blows (opens) it will open the entire circuit and stop current through the component(s). A fuse connected in one branch of a parallel circuit, of course, would not affect current through any of the other branches.

The main role of fuse used in series with any electrical appliance limits the current through the appliance. It protects the appliance due to short-circuiting or over / loading as when current exceeds the limit for which the fuse is rated, it blows off and the appliance is disconnected from the electric supply, When a fuse with defined rating for a particular appliance is replaced by one with larger rating, it does not blow off and the appliance is damaged due to larger current passing through it.

The fuse is rated for a certain maximum current and blows off when a current more than the rated value flows through it.

If a fuse is replaced by one with larger ratings, the appliances may get damaged while the protecting fuse does not burn off. This practice of using fuse of improper rating should always be avoided.

Most reactive metals belonging to group I of the periodic table are Sodium and Potassium. Their symbols are “Na” and “K”.

Electron dot structure – valence electrons are represented by dots placed around the chemical symbol. Electrons are placed up to two on each side of the elemental symbol for a maximum of eight, which is the number of electrons in a filled s and p shell. We place a single electron on each side before pairing them up (this is related to Hund’s rule). Period one (hydrogen and helium) represents an exception where only a maximum of two electrons are placed on one side of the element.

Electron dot structure for sodium:

Reaction of Na with halogen (eg: Chlorine)

Formation of sodium chloride:

STEP 1: Formation of cation-

STEP 2: Formation of anion-

STEP 3: Formation of NaCl-

Properties of NaCl:

• This compound is a solid and is somewhat hard because of strong force of attraction between the positive- positive ions. It is generally brittle and breaks into pieces when pressure is applied.

• NaCl has high melting and boiling point because a considerable amount of energy is required to break the strong inter-ionic attraction.

• It is generally soluble in water.

• It conducts electricity in molten state because the movement of ions is possible.

Certain compounds contain only carbon and hydrogen. so these organic compounds are called hydrocarbons.

Hydrocarbons are the simplest organic compounds. Containing only carbon and hydrogen, they can be straight-chain, branched chain, or cyclic molecules.

Carbon tends to form four bonds in a tetrahedral geometry. Hydrocarbon derivatives are formed when there is a substitution of a functional group at one or more of these positions.

There are three types of homologous families of hydrocarbons: alkanes, alkenes and alkynes. Alkanes contain only single bonds between carbon atoms. Alkenes contain at least one double bond. Alkynes contain at least one triple bond. Most of these types of hydrocarbons can exist with the same chemical formula in different form or chemical structure. When a compound has the same chemical formula but two possible structures, these two structures are called isomers.

Derivatives of Hydrocarbons-An almost unlimited number of carbon compounds can be formed by the addition of a functional group to a hydrocarbon.

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon, and thus are group 14 hydrides. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls.

Addition reaction or hydrogenation converts alkenes into alkanes.

For example:

C2H4 (ethane) +H2 (hydrogen) →C2H6 (ethane)

a. Reflex action or reflex is an involuntary action in response to a stimulus. This is a spontaneous action without thinking. For example, we adjust our eyes when exposed to bright light. Peripheral nervous system (PNS) is a system of nerves which connect central nervous system (CNS) (includes brain and spinal cord) with other parts of the body. Reflex action is the result of coordination of spinal cord and peripheral nervous system. This action does not involve the brain. The pathway in which impulses travel during the reflex action is called a reflex arc.

b. An action potential never travels to the brain for processing and so results in a much quicker reaction.

When a stimulus is encountered, the signal from that stimulus will travel up the sensory neuron to the spinal column. There, it will likely pass

through a short interneuron before continuing down a motor neuron to the origin of the signal. Then, a contraction of the muscles is triggered, moving the hand.

c. Dendrites of the neutron receive the information and it is nothing but it requires information that are part of the neuron family.

Likewise, the Axon of the neuron information travels as fast as electrical impulse taken by the dentritis action.

It has been emerged with neuron information and travels through the Axon.

Dendrite → cell body → axon to its ends.

When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch to three feet or more. Many axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon.

ii. The plant hormone which is synthesised at the shoot tips is auxins. When growing plants detect light, hormone auxin, synthesised at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light.

It can be explained by help of this diagram. This kind of movement is induced by light. The stem mostly grows and turns towards the source of light, therefore it is said to be positively phototropic. Auxin distribution controls phototropism.

In 1, Sunlight strikes the plant from directly above. Auxin (pink dots) encourages growth straight up. In 2, 3, 4, Sunlight strikes the plant at an angle. Auxin is concentrated on one side, encouraging growth at an angle from the preceding stem. More growth of the stem on the shaded side is due to more accumulation of auxin on the shaded side than on the illuminated side.

This unequal distribution of auxins on the two sides may be due to following two reasons:

(i) Translocation of auxins from illuminated side to the shaded side.

(ii) Inhibition of auxin synthesis in the illuminated side (light side).

OR

They are many kinds of plants of which the climbers and creepers are considered movable plants. While creepers are plants that spread on the ground and climbers need a support structure for their growth. The support could either be a structure, a plant or a tree. Grapes, members of squash, melon family, cucumber and sweat pea are few examples of common tendril producing plants.

Certain vines use tendrils to climb towards the sun. Tendrils are specialized shoots, leaflets or leaves that are highly sensitive to touch. The effect of tendrils is to move the plant towards an object that it can cling to. So tendrils provide the plants a way of changing its position. As soon as it makes contact with a firm support, it secures its tight hold with a great speed. Growth on the side of origin of the tendril touching the support virtually stops but on the other side it may some 200 times as fast as normal.

When they form initially, they are almost straight. Then while growing it waves around. This process is called circumnutation. The direction of cirumnutation could be clockwise or counter clockwise depending on the species. The tip of the tendril is sensitive to auxin which is a growth stimulating chemical hormone. Auxin causes the tendrils to coil getting involved in the asymmetrical growth around the support

The part of the tendril in contact with the support doesn't grow as fast as the other part of plants; it coils around the support with the help of plant hormone called Auxin. This causes the tendril to coil around the support. The unequal growth is due to more secretion of auxin in the other end and less secretion in the end in contact with the support.

ii. The growth of a plant part due to chemical stimulus is known as chemotropism

'Chemotropism is growth of organisms such as bacteria and plants, navigated by chemical stimulus from outside of the organism or organism's part. The response of the organism or organism part is termed ‘positive’ if the growth is towards the stimulus or ‘negative if the growth is away from the stimulus.

An example of chemo-tropic movement can be seen during the growth of the pollen tube, where growth is always towards the ovules. It can be also written that conversion of flower into fruit is an example of chemotropism.

Fertilization of flowers by pollen is achieved because the ovary releases chemicals that produce a positive chemo-tropic response from the developing pollen tube.

An example of positive and negative chemotropism is shown by a plant’s roots; the roots grow towards useful minerals displaying positive chemotropism, and grow away from harmful acids displaying negative chemotropism.

There are some possible reason due to this defect of vision may have arisen:

(a) Elongation of eyeball

(b) Excessive curvature of the lens.

(a) Student unable to see distinctly the objects placed beyond 5m from his eyes because student suffering with myopia. A myopic eye can't see distinct object clearly but able to see nearby object clearly.

(b) Convex lens of suitable focal length is used to restore proper vision. After using convex, image formed at retina. While before it, image was formed near the retina. As shown in figure it is clear how the lens correct this type of defect.

ii. Focal length of convex lens is positive

So, f = +5m

The dioptre is the unit of measure for the refractive power of a lens. The power of a lens is defined as the reciprocal

of its focal length in meters, or D = 1/f, where D is the power in dioptres and f is the focal length in meters.

Now, Power can be calculated as:

Hence, power is +0.2 dioptre

Magnetic field lines through a current carrying conductor loop are along its axis at its centre. As the solenoid of big length and small radius has a number of coils carrying the same current and have no gaps in between the windings, the magnetic lines add up.

The resulting magnetic field lines inside the solenoid become more or less uniform and aligned along the axis of the solenoid. At the edges they tend to diverge towards the opening. Outside the solenoid the effects of the neighbouring windings cancels out the magnetic field to zero.

ii. This principle is utilised to magnetise a piece of magnetic material like soft iron when placed inside the coil.

Can be used as an electromagnet-

Thus the cylindrical area inside a solenoid is an electromagnet by itself. We can also wrap a solenoid around a ferromagnetic material like iron, say, over half or full length of the bar. The bar can be bent in a shape of a "U"or a "horse shoe" or a "circle". Then the air gap between the two ends can be used as a magnetic field.

The empty solenoid can be bent in a shape of a horse shoe also.

iii. The strength of the electromagnet above is increased by adding more number of windings to the solenoid, increasing the number of windings per unit length, increasing the current, decreasing the diameter of solenoid.

It can be increased also by introducing a ferro-magnet of high paramagnetic property inside the solenoid.

It can be increased by adding another solenoid of larger diameter around the solenoid.

The strength of an electromagnet can be increased by immersing the solenoid and surroundings inside a paramagnetic fluid of high permeability.

B = μ₀ μ n i , n = windings/unit length, i = current

OR

An electric generator converts mechanical energy into electrical energy. Alternating current generators or AC generators produce alternating current. Principle: It works on the principle of electromagnetic induction. Whenever the magnetic flux through a coil changes, induced current is produced.

Construction: Alternating current generator consists of a rectangular coil ABCD called armature. The armature coil consists of large number of turns of insulated copper wire wound over a soft iron core. The coil is kept between the poles of a strong magnet. In the figure shown R1 and R2 are two slip rings connected to the two ends of the coil and convey the current produced to outside circuit. B1 and B2 are two carbon brushes remain in sliding contact with slip rings.

Working: The coil of the generator is rotated with the help of an axel. When coil rotates, it cuts the magnetic lines of force (magnetic field) near the north (N) and south (S) poles of the magnet. By electromagnetic induction, a current is induced in the coil. The direction of this current is given by Fleming’s right hand rule. As this coil turns clockwise, arm AB moves up and arm CD goes down. The direction of current is from A to B in AB and C to D in CD. The induced current is taken out through slip rings and carbon brushes. After half this rotation, AB and CD interchange their position. Now CD moves upward and AB downward. The direction of induced current is from D to C in CD and B to A in AB, during this half rotation. The slip rings R1 and R2 also rotate along with the coil ABCD. Thus, their polarities keep changing after every half rotation. Thus, the current changes its direction twice in one complete revolution of the coil. Such a current which changes its polarity after fixed intervals is called alternating current.

Function of Brushes: The brushes B1 and B2 remain fixed in their positions and maintain sliding contacts with the rotatable slip rings R1 and R2 respectively. It is through these brushes that the current induced in the armature coil is fed to the external circuit by means of line wires.

a. As with all of Nature it is a symbiotic factor in a greater whole, and an element all life depends on. As we degrade our soils, poison our land and remove the natural catchments for runoff through deforestation and removal of trees; as we fill in our waterways and natural filtering systems in the name of development and progress; as we dam up rivers destroying natural eco-systems, we completely upset the natural scheme of things that water needs to flow and filter clean water for us all.

Two ways of creating awareness are:

• Door to door campaigning.

• Nukkad natak/any other methods.

• Check for leaking pipes and faulty taps in your neighbourhood.

• Introduce rainwater harvesting systems.

• Work as a community with social groups and NGO’s.

b. Groundwater is the water present beneath Earth's surface in soil pore spaces and in the fractures of rock formations.

Water scarcity, including depleting levels of ground water is a subset of problems associated with climate change and unfortunately both of them are global man-made disasters. To overcome this problem, huge investments in infrastructure as well as institutions are required. As serious as it may sound, there still is time to repair the damage done.

These are some ways in which we can maintain underground water table:

• Water in flood hit areas or areas with water adequacy can be channelized underground using some form of innovative designs to replenish aquifers. This water can be used up during dry seasons using the age old tube well mechanism.

• Rain water harvesting should be extensively adopted wherever possible.

• Remote sensing should be incorporated across multiple platforms. It has become easier to predict now, where and up to what extent flood or drought will strike. Using remote sensing data, the levels of underground water can also be judged remotely. This data can be transmitted to local bodies and farmers so that the use of water can be better planned. Mobile applications can play a key role here in transmitting data. If farmers already know that they are going to get less water for a particular harvest cycle, they can sow crops which require less water like oil seeds or pulses. The entire process is not high on investment and is easy to incorporate.

• Drip irrigation requires 35-40% less water than flood irrigationonly with a small investment. Government plans to boost drip irrigation will help lower water scarcity.

• Reduction of unnecessary water usage on the industrial scale needs to be monitored. The release of effluents and toxic chemicals in water is being monitored well, but a mechanism to check the usage of water in the first place needs to be re-looked.

• Processes that turn salt water to fresh water such as Desalination and Per-vaporization are high on energy demands and hence cost making them unfeasible. Some innovation in the plant design or energy savings such that these processes can become feasible will help boost the production of fresh water.

• And most importantly: awareness about using water judicially needs to be there. Awareness leads to curiosity which further leads to science.

ii. Water harvesting is the collection of runoff for productive purposes. Instead of runoff being left to cause erosion, it is harvested and utilized. In the semi-arid drought-prone areas where it is already practised, water harvesting is a directly productive form of soil and water conservation.

Advantages of water harvesting at the community level are as below

• Water harvesting improves the quality of ground water. There stored water provides moisture and helps in improving vegetation in and around the area. It also prevents soil erosion, floods.

• Water harvesting in rural areas not only increases the agricultural production but also increases the life of downstream dams and reservoirs.

• Ground water generally does not get polluted, if it is away (at least 20 mtr.) from the sanitary works. The water gets filtered while percolating through sand & stones. Therefore groundwater remains pure and clean.

• Since bore well is closed, no risk of getting contaminated.

• Since it is closed no danger of children or animals falling into it.

• Temperature of deep water remains stable. It feels cool in summer and warm in winter.

• Since bore are deep, chances of water remaining available in summer are more.

pH is a measure of acidity or basicity of an aqueous solution.

It is a mathematical notation that describes the power of an acid or a base. The concentration of the acid is represented as [H⁺] or [H₃O⁺]

pH = – log [H⁺] (or)

pH = – log [H₃O⁺]

The pH scale is the range of pH values from 0 to 14. The paper that indicates the complete range of pH value from 0 to 14 is called the universal indicator. pH paper is a strip of filter paper that is soaked in universal indicator and then dried.

When the pH value is between 0 and 7, it indicates the acidic range of the solution. When the value is between 7 and 14, it represents the basic or alkaline range of the solution. When pH = 7, it is called a neutral solution. The decrease of pH value indicates the increase of acidity and the increase of pH value shows the increase in alkalinity. Water is neutral and its pH is equal to 7.

Hence according to the question, he infers that A is sodium carbonate solution and B is acetic acid. The pH paper turns blue when dipped in solution A, it means A is a strong base having pH 9 and the pH paper turns orange when dipped in solution B, it means B is a strong acid having pH 4.

OR

pH is a measure of acidity or basicity of an aqueous solution.

pH paper is a strip of filter paper that is soaked in universal indicator and then dried.

From the samples what student has collected to test the pH value, washing soda is wrong selection.

Hence, the teacher was referring to washing soda because it is in powder form not in liquid form. To find pH using pH paper, the sample should be in liquid form.

Rest others - dilute hydrochloric acid, lemon juice, and soap solution are all in a liquid state and hence are good to be used for pH indication.

When the pH value is between 0 and 7, it indicates the acidic range of the solution. When the value is between 7 and 14, it represents the basic or alkaline range of the solution. When pH = 7, it is called a neutral solution. The decrease of pH value indicates the increase of acidity and the increase of pH value shows the increase in alkalinity.

Light is one of the requirements for photosynthesis. When a part of the leaf is covered from both upper and lower sides with a black paper strip, the light will not reach to covered part. Hence, photosynthesis will not take place in the covered part of the leaf. On the other hand, as light will be available to uncovered part of the leaf, cells of this region will carry out photosynthesis actively and hence, glucose will be synthesised in the uncovered part of the leaf. In the leaf, a part of this glucose is utilised to carry out various metabolic activities and rest of the amount converts into starch. Presence of starch in the leaf, which can be detected by performing the iodine test, indicates the occurrence of photosynthesis.

6CO₂ + 12H₂O + Chlorophyll / Sunlight →C₆H₁₂O₆ + 6H₂O + 6O₂

This procedure should be followed:

1. Take the potted plant and keep it in the dark place for 2-3 days so that the leaves get destarched.

2. Cover a part of one of its leaves with the strip of black paper. Make sure that you cover both the sides of the leaf.

3. Now place this plant in sunlight for 3—4 hours.

4. Pluck the selected covered leaf and remove the black paper covering it.

5. Place this leaf in the beaker containing water and boil it for about 10 minutes.

6. Take out the leaf and now boil it in alcohol, using the water bath, for 10 minutes. This removes the chlorophyll.

7. Take out the leaf and wash it under running water.

8. Place this leaf in the Petri dish and put a few drops of iodine solution on it. Now observe the change in colour.

Observations:

The leaf turns blue-black except in the covered region. As this covered region did not receive light, photosynthesis did not occur. Hence no starch was formed there. The uncovered region received light and starch was formed there due to photosynthesis.

Result:

This tells us that light is essential for photosynthesis.

Hence Student D made the right suggestion because destarching of the leaf by keeping the plant in darkness before starting the experiment is essential. Because then only photosynthesis the process of making food will occur efficiently.

According to the Ohm’s law, the potential difference (V) across the ends of a resistor is directly proportional to the current (I) through it provided its temperature remains the same. That is

Here R is a constant for the given resistor at a given temperature and is called its resistance. The SI unit of resistance is ohm (W). A graph between the potential difference across the two ends of a resistor and the current through it is a straight line passing through the origin. The slope of this graph gives the resistance R of the resistor. To verify the Ohm’s law, we measure the potential difference across the two ends of a resistor at different currents through it in an electric circuit. The current through the resistor is measured by connecting an ammeter in series with it. The potential difference across the two ends of the resistor is measured by connecting the voltmeter in parallel with it.

Hence, If a student while studying the dependence of current on the potential difference keeps the circuit closed for a long time to measure the current and potential difference, then:
(a) Ammeter’s zero error will change
(b) Ammeter’s will give more reading
(c) A voltmeter will show constantly higher readings
(d) The resistor will get heated up, and its value will change

As the current flows for a long time, the resistor will get heated up, and its value will change as resistance depends on temperature.

Raw Materials required for the preparation of soap in the laboratory:

⇒ Vegetable oil

⇒ Sodium Hydroxide

⇒ Common salt

⇒ Beaker

⇒ Bunsen Burner.

• The reaction between vegetable oil and sodium hydroxide solution is exothermic in nature because heat is liberated during the reaction.

• The white suspension formed is made up of soap and glycerol. The process of formation of soap is called saponification.

• Test using red and blue litmus papers shows that soap suspension is basic in nature and not acidic in nature.

• The process of precipitation of soap from the suspension is called salting out.

To determine the nature of reaction mixture of saponification reaction we can dip a litmus paper, red litmus will turn blue indication the alkaline nature of reaction mixture.

Asexual reproduction is the primary form of reproduction for single-celled organisms such as the Achaea, bacteria, and protists. Many plants and fungi reproduce asexually as well. Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only. The offspring will be the exact genetic copies of the parent.

New organisms are produced in rapid multiplication by the process of amitotic or mitotic divisions. Amitosis is the process by which a cell directly separates, as the nucleus and cytoplasm are directly cut in two. Mitosis is the process by which a cell, which has previously replicated each of its chromosomes, separates the chromosomes in its cell nucleus into two identical sets of chromosomes; each set will have its own new nucleus. It is a form of nuclear division.

Binary fission and budding are two common methods of asexual reproduction. Binary fission is found in unicellular organisms like Amoeba, Paramecium and Euglena, to name and few. Budding is found in Yeast and Hydra.

Binary fission in Amoeba

Amoeba is a shapeless tiny unicellular organism that has a porous cell membrane which encloses the cell organelles and cytoplasm. Amoeba reproduces by the common asexual reproduction method called binary fission. After replicating its genetic material through mitotic division, the cell divides into two equal sized daughter cells. The genetic material is also equally partitioned; therefore the daughter cells are genetically identical to each other and the parent cell. In this process, the nucleus of the Amoeba first divides to form two daughter nuclei by the process of Karyokinesis. After the nucleus has divided into two, the process of Cytokinesis takes place in which the cytoplasm in the mother cell divides into two daughter cells. This leads to the formation of the two daughter Amoebae cell having a nucleus and its own cell organelles.

Karyokinesis is the process of the division of the nucleus. It corresponds to the separation of the daughter chromosomes into two daughter nuclei. Karyokinesis is usually followed by Cytokinesis.

Cytokinesis is the process of the division of the cytoplasm. It corresponds to the separation of the daughter nuclei into two daughter cells. Cytokinesis occurs immediately after mitosis.

Visible light, also known as white light, consists of a collection of component colours. These colours are often observed as light passes through a triangular prism. Upon passage through the prism, the white light is separated into its component colours - red, orange, yellow, green, blue and violet. The separation of visible light into its different colours is known as dispersion.

The colours of the spectrum observed on the screen are in the order:

The statement made by the student is incorrect. Positions marked 3 (yellow), and 5 (blue) are similar to the colour of gold metal and the colour of the sky respectively. The student is stating the nature of colours in reverse order.

ii. (a) The position marked 7 (violet) corresponds closely to the colour of brinjal. It is due to the solution of potassium permanganate which gives its violet colour.

(b) Danger or stop signal lights are red. So position 1 corresponds to this colour.

The primary reason why the colour red is used for danger signals is that red light is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a colour. So red light can travel the longest distance through fog, rain, and the alike.

When there is a lack of oxygen, anaerobic respiration takes place in the muscle cells that produces lactic acid due to which cramps are common. Lactic acid accumulation can cause lactic acidosis responsible for muscle fatigue.

Anaerobic respiration in muscles: Pyruvate is converted to lactic acid.

(Anaerobic respiration is a respiration which takes place in absence of oxygen and instead other electron acceptors are used.)

The method by which Hydra reproduces is called budding.

Budding is an asexual method.

A new bud grows out of the side of the body of the Hydra and this new bud is formed by repeated mitotic divisions of the cells. This is nourished with food from its parent. The bud grows to form a new Hydra with mouth and tentacles and eventually it breaks away from the parental Hydra forming an independent Hydra.

i) Valency: Valency is the power of an atom to combine with another atom by donating or receiving electrons in their outermost shell or Valency is the number of electrons gained or lost by an element to achieve stable noble gas configuration which is a fully filled octet.

For example: The electronic configuration of element Magnesium is: 2,8,2. The number of valence electrons in the outermost shell here as we can see is 2. Therefore the valency of element Magnesium is 2.

(Electronic configuration: It is the distribution of electrons of an atom or molecule in respective molecular or atomic orbitals.)

ii) Atomic size: This is the distance between the centre of the nucleus of an atom to its outermost shell. Hence when the number of shells increases, the atomic size increases too as the distance from the centre of the nucleus to the outermost shell increases.

∠i = angle of incidence

∠r = angle of refraction

C = centre of curvature

P = principal focus

Biodiversity is the diversity of biological organisms (plants and animals) living in a particular regionor an ecosystem or anywhere around the world.

Two advantages of conserving forest and wildlife are:

i) When biological diversity is maintained, or forest and wildlife is conserved it in turn leads to conservation of ecological diversity.

ii) Forests are a source of a lot of essential items that we use in our daily lives like medicines, wood and controls soil erosion etc. whereas wildlife plays a role in balancing the ecosystem and various food web chains.

i) When aluminium (Al) and dilute hydrochloric acid react a large amount of heat is produced in the reaction i.e. the reaction is exothermic hence temperature of the reaction mixture rises. (Aluminium replaces the Hydrogen as it is more reactive than hydrogen to form aluminium chloride.)

2Al+6HCl → 2AlCl₃ + 3H₂

ii) Sodium is a very reactive metal and reacts vigorously with dilute hydrochloric acid to form sodium chloride. This reaction is exothermic (liberation of heat) and is hence highly explosive.

2Na + 2HCl → 2NaCl + H₂

where Na is sodium metal, HCl is hydrochloric acid and H₂ is hydrogen gas.

iii) When lead (Pb) reacts with hydrochloric acid (HCl), lead displaceshydrogen from hydrochloric acid (since lead is placed above Hydrogen is reactivity series and is hence more reactive that Hydrogen) slowly to form lead chloride (PbCl₂₎ with liberation of hydrogen gas (H₂). The bubbles of gas seen is of hydrogen gas.

Pb + 2HCl → PbCl₂ + H₂

X: This is Chlorine (Cl₂) gas

Y: This is Bleaching powder or calcium hypochlorite(CaOCl₂)

NaOH is used in many industrial processes. One of the most popular methods in salt water brine (ratio of salt to water for a brine is 4 tablespoons of salt per 4 cups of water.)

Chemical equations of the reactions involved are as follows:

I) 2NaCl + 2H₂O → 2NaOH + Cl₂ (X) + H₂

II) Cl₂ (X) + Ca(OH)₂ → CaOCl₂ (Y) + H₂O

where NaCl is sodium chloride, H₂O is water, NaOH is sodium hydroxide, Cl₂ is chlorine gas, Ca(OH)₂ is calcium hydroxide and CaOCl₂ is bleaching powder.

Atomic number of Sodium: 11

Atomic number of Magnesium: 12

Atomic number of Aluminium: 13

Electronic configuration of the given elements:

Na(Sodium) : 2,8,1 (11 electrons)

Mg(Magnesium): 2,8,2 (12 electrons)

Al (Aluminium): 2,8,3 (13 electrons)

i) Valency is the power of an atom to combine with another atom by donating or receiving electrons in their outermost shell or Valency is the number of electrons gained or lost by an element to achieve stable noble gas configuration which is a fully filled octet. Aluminium has the highest valency since it loses three valence electrons to attain stable electronic configuration of a noble gas.

ii) Sodium has the largest atomic size. We know that atomic size decreases on moving from left to right across a period due to increase in nuclear charge decreasing the atomic size.

iii) Maximum chemical reactivity is of sodium (Na) because as we can see that all the three elements are metals and the chemical reactivity of these elements is determined by their metallic character (tendency to lose electrons). We know that the tendency to lose electrons decreases from left to right across a period hence sodium has the highest chemical reactivity.

OR

I) Valency of group I elements is 1. And valency of oxygen is 2. Hence, formula of oxides of group I elements is A₂O (where A is the group I element and O is oxygen).

II) Valency of group 13 elements is 3. And valency of halogens (halides) is 1. Therefore, the formula of halides of group 13 elements is MX₃ (where M is the group 13 element and X is the halogen).

III) Valency of element of group 2 is 2 and that of group 16 is also 2. Hence, the formula of the compound formed is X₂Y₂or XY. (where X is the element of group 2 and Y is the element of group 16).

Part A:Stomatal pore

Function: It allows a plant to take in carbon dioxide or participate in gaseous exchange, needed for photosynthesis. It also helps to reduce water loss by evaporation i.e. checks excess of transpiration (excess water loss through aerial parts of the plant in form of water vapor).

Part B: Guard cells

Function: These are specialized cells. The opening and closing of the stomata or the stomatal pore is controlled by the guard cells.

OR

In the body, fats are digested in the small intestine. The small intestine receives secretions from the liver (bile) and the pancreas. Bile breaks down the large globules of fat into smaller globules of fat (on which pancreatic enzyme can now work on) and this process is called emulsification of fats. The intestinal wall secretes intestinal juices and along with the pancreatic enzymes, further break down the fat globules to fatty acids and glycerol.

i. The functions of the following parts of human male reproductive system are:

a) Testis: Testis is the male reproductive organ located in the scrotum. The primary function is production of sperms (Seminiferous tubules are present in the testes where sperm is produced) and also controlling the male hormone testosterone that gives secondary sex characteristics to males at puberty like facial hair .

b) Vas deferens: This helps transport mature sperm from the testes (specifically the epididymis where sperms are stored) to the urethra to the ejaculatory ducts for ejaculation while secretions from the male accessory sex glands (seminal vesicles, prostate, bulbo-urethral glands) are collected forming semen.

c) Urethra: It is a tube extending from the urinary bladder, through the length of the penis to its external opening. It serves as a passage for urine. It also has the function of ejaculation semen during ejaculation.

d) Prostate: Prostate gland lies below the urinary bladder and surrounds the urethra. Prostate gland produces prostate fluid (alkaline) which is one of the components of the semen making up about 13-33% of the same.

ii) Two common pubertal changes that appear in human males are:

The vocal cords double in length resulting in lowered pitch in males, pubic hair develops, hair appears in face, chest etc. Sweat glands also develop in the armpit.

Many traits are inherited but not expressed in an organism, these are the recessive traits while those that get expressed are called dominant traits. Mendel explained that it is possible that a trait is inherited but not expressed in an organism by his experiment on monohybrid inheritance.

He crossed a tall plant (TT) with a dwarf plant (tt) and all tall plants were produced in the first progeny. But when these were now crossed amongst themselves, not all plants were found to be tall. Some were dwarf. (Inheritance of both traits in F2 progeny which were not observed in F1 progeny). Hence traits inherited may not always be expressed.

Classification is categorizing organisms in taxonomic groups according to their observed similarities for ease of understanding while evolution is the change in heritable characteristics over a number of generations.

The modern classification system is based on the phylogenetic resemblances and evolutionary relationships between the different species of organisms present in the world. The more common characteristics two species have, the more closely related are they. Thus, evolution of organisms gives us a knowledge about the position of the organism in the modern system of classification and is a reflection of the classification. So, it can be said that evolution and classification are interlinked.

If the image formed by a lens for all positions of an object placed in front of it is always erect and diminished, the nature of the lens is concave lens.

Ray diagram justifying the same is as follows:

Given: Power of the lens (P) is -10D (since concave lens hence negative sign is introduced).

Therefore focal length (f) is calculated in the following way:

Hence the focal length is -0.1m or -10cm.

Power dissipated by the resistor of 2 ohm (P) = i²R (where i is the current through the resistor and R is the resistance of the resistor.)

Therefore: i² = P/R =(18/2) A = 9A

⇒ i= 3A

Resistances B and C are connected in parallel, therefore, the current is equally divided in between them i.e. 1.5A.

OR

The effective resistance across the resistors of 4 ohm connected in parallel is:

R_eq=

The resistance is equal hence same current will flow through these. Hence the potential difference across the parallel combination and the 2Ω resistor is the same.

Parts where the strength of the magnetic field is

i) maximum: part A and part C

ii) minimum: part B

Part B has no magnetic field lines whereas part A and part C has magnetic lines since they are magnetic poles which determines the strength of their magnetic field. Hence part B is where the intensity of the magnetic field is almost zero or minimum.

i. A) The nature of bond between A and B will be ionic, as transfer of electrons is taking place forming an ionic compound.

(Ionic bond is a bond formed between two dissimilar atoms that have a large electronegativity value difference in between them. One atom loses electrons while another atom gains electrons to acquire a stable electronic configuration. )

B) The formula of the compound formed between A and B is AB₂. (A loses electrons while B gains one electron)

ii) Magnesium chloride or MgCl₂ is an ionic compound. Ionic compounds are formed due to the electrostatic force of attraction between oppositely charged ions. Magnesium chloride is made of Mg²⁺ and Cl^- ions. One atom of magnesium has 12 electrons so when it loses two electrons, the number of electron sin the outermost shell is 8 electrons. Similarly, an atom of chlorine has 17 electrons so when it gains one electron, the number of electrons in the outermost shell now is 8. (Magnesium forms cation with charge +2 while Chlorine forms anion with charge -1) So therefore two chlorine anions form an ionic bond with one magnesium cation to form MgCl₂.

iii) Common salt conducts electricity only in the molten state because for conduction of electricity, charged ions must be present in free state so that they can move about freely conducting the electricity. In ionic compounds like common salt or sodium chloride, the ions are not free but are ionic bonded in a crystal lattice hence cannot conduct electricity. However when they are in a molten state, ionic compounds (here NaCl) dissociates into Na⁺ and Cl^-, these ions have mobility and are charge carriers and therefore common salt in the molten state can conduct electricity.

iv) Sodium combines with chlorine forming sodium chloride by ionic bond. This leads to a crystal lattice with a regular arrangement of ions held by strong forces. There is a strong electrostatic attractions between the positive and negative ions hence a lot of energy is required to overcome them hence the melting point is high.

Ionic bonds are formed between dissimilar atoms by transfer of electrons. The number of electrons gained or lost is to achieve stable noble gas configuration. The atomic number of carbon is 6. It has 4 electrons in its outermost shell (Electronic configuration: 2,4) hence would need 4 more electrons to attain stable noble gas electronic configuration.

If it would have given four electrons, C⁴⁺ cation would have been formed but this is not possible as the removal of four valence electrons requires a huge amount of energy, leaving behind six protons in the nucleus of the carbon cation. This would make it highly unstable.

If it would have taken four electrons, Carbon would have formed C⁴⁻ anion, but it is difficult for its nucleus to hold 6 protons and 10 electrons. Hence this is also not feasible.

Thus, carbon achieves stable noble gas electronic configuration by sharing its four valence electrons forming covalent compounds by covalent bonding. (Covalent bonding: Bond formed by sharing electron pairs between atoms with low electronegativity difference or almost same electronegativity).

The type of bonds formed in ionic compounds is ionic bond and in the compounds formed by carbon is covalent bond.

Carbon compounds are bad conductors of electricity because they are covalent compounds formed by covalent bonding. They lack free electrons needed for conduction of electricity.

OR

i) Functional group in a carbon compound: Groups attached or bonded to a carbon atom in a carbon compound that defines the chemical property of the compound is called a functional group.

The functional group present in:

a) Ethanol (C₂H₅OH): (Hydroxy group: -OH group)- Alcoholic group

Structure:

b) Ethanoic acid (CH₃COOH): (Carboxyl group: -COOH) - Carboxylic acid.

Structure:

ii. Name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place are:

i) Alkene: (C_nH_2n)

ii) Alkyne: (C_nH_2n-2)

Essential conditions for an additional reaction to occur are:

a) Multiple bonds must be present between the carbon atoms for addition reactions to take place.

b) Catalysts are required for addition of hydrogen or other halogens or atoms to the reaction.

Chemical equation of such a reaction:

CH₂=CH₂ + H₂ -> CH₃ + CH₃ (in presence of catalyst like platinum or nickel)

where CH₂=CH₂ is ethene (reactant), H₂ is hydrogen and CH₃-CH₃ is ethane (product).

i) The part of brain which controls

A. voluntary action is cerebellum.

It controls and coordinates voluntary movements like body posture, balance, coordination, etc.

B. involuntary action is medulla.

It deals with autonomic functions of the body like breathing, heart rate etc.

ii) The peripheral nervous system is responsible for connecting the Central nervous system to the sensory and other organs of the body. Information is carried via the nerves of the PNS to and fro from the CNS to the organs.

The components of this nervous system are: the somatic nervous system and the autonomic nervous system and all the nerves lying outside the brain and spinal cord. The somatic nervous system is composed of nerves connecting the voluntary skeletal muscles to the sensory receptors of the body. The autonomic nervous systemhas the sympathetic and para-sympathetic nervous system responsible for regulating involuntary body functions.

The Autonomic Nervous Systemregulates the connections between the brain, spinal cord and organs, on the other hand, the Somatic Nervous System connects the external sensory organs through the brain and to the muscles.

iii) The glands that secrete:

• Insulin - Islets of Langerhans within the pancreatic gland.

• Thyroxin- Thyroid gland

The timing and amount of hormone secreted are regulated in human body. For example: Insulin is a secretion by the pancreas. It is responsible for maintaining the glucose level in the blood. If glucose level is high, more insulin is secreted and vice versa. Hormonal secretion is regulated by feedback mechanism. Another example is of parathyroid that secretes parathormone to raise the calcium level in the serum. When serum level gets high then negative feedback mechanism comes into play and signal is passed to decrease the secretion of the parathormone.

i) The parts of the human eye controlling the amount of light entering it are:

Iris and Pupil.

Iris is the part of the eye surrounding the pupil. It adjusts the size of the pupil based on the intensity of light received by the eye. (contracts the eye if light received is large, dilates the pupil if light received by the eye is less.

Pupil is the opening in the iris through which light passes before reaching the lens and getting focussed at the retina. Hence the pupil allows light to enter the eyes.

ii) Retina is a thin and delicate tissue lining the inner eye. It varies in thickness from 0.1mm to 0.5 mm (thickest near the optic disk). The sensory photoreceptor cells i.e. rods and cones are present here. These generate excitatory responses to light and sends electrical signals to the brain due to which visual information is processed. The retina thus also acts as a screen on which image is formed.

iii) Yes, the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye.

We can encourage eye donation because of a number of reasons and the following initiatives can be taken:

a) Various campaigns can be conducted to support the cause.

b) Millions of people are suffering from corneal blindness hence donating an eye can be helpful for them who can see with those eyes donated since eyes are functional even after death of a person so people can be encouraged to donate their eyes after death.

i) Electromagnetic induction is the generation or creation of electromotive force across an electrical conductor when there is a change in the magnetic field.

ii)

A. As Current in the coil P is started by closing the key there is a change in the associated magnetic field. This hence changes the magnetic field around region/coil Q too. Due to this there is a generation of induced electric current in the coil leading to the deflection of the galvanometer G.

B. As current continues to flow in coil P, there is no change in magnetic field or rather the magnetic flux does not change hence galvanometer shows no deflection.

C. When current in coil P is stopped by removing the key, current reaches to the zero value thus changing the associated magnetic field too due to change in current. This would bring about change in magnetic field around coil Q, electrical current gets induced and hence galvanometer shows deflection.

OR

The activity to plot the magnetic field lines around the bar magnet employes iron fillings, iron fillings are used because iron is a magnetic material and it gets attracted by a magnet. The following steps are executed to demonstrate the activity: -

1. Fix a sheet of white paper on a drawing board using some adhesive material.

2. Place a bar magnet in the centre of it.

3. Sprinkle some iron filings uniformly around the bar magnet. A salt-sprinkler may be used for this purpose.

4. Now tap the board gently.

Observations The iron filings arrange themselves in a pattern as shown in the diagram. The magnet influences the filings in the region surrounding it. Therefore the iron filings experience a force. The force thus exerted makes iron filings to arrange in a pattern. The region surrounding a magnet, in which the force of the magnet can be detected, is said to have a magnetic field. The lines along which the iron filings align themselves represent magnetic field lines around the bar magnet.

A region A has magnetic field lines relatively closer than another region B. Therefore region A has more stronger magnetic field compared to region B because as we know that the strength of a magnetic field is directly proportional to the closeness of the field lines and since field lines are closer in region A hence it is having a stronger magnetic field.

i) The Chipko movement was started in April 1973 in Reni village in Uttarakhand where the villagers prevented cutting of trees by embracing the trees. It was an initiative by Sunder Lal Bahugana to stop exploitation of forests.

Forests should be conserved for a variety of reasons since they are sources of essential items like medicine, food, wood etc. Forests prevent soil erosion, prevents floods, prevents global warming and maintains ecological balance.

ii) The four changes that I would like to incorporate in the life-style of students of my age to move towards a sustainable use of available resources are:

a) Support afforestation and prevent deforestation.

b) Encourage rainwater harvesting in the society.

c) There should be two separate bins: one for throwing biodegradable wastes and another for non-biodegradable wastes.

d) Encourage students to cycle or use pool cars for shorter distances instead of motor vehicles or individual cars.

e) Recycle papers and plastic as and when possible.

iii) The three R's he mentioned were:

Reduce, Reuse and Recycle.

These can be followed in a number of ways:

REDUCE:

a) Reusable water bottles should be used.

b) Reduction of plastic bags usage.

c) Electronic mails can be used instead of paper mails.

d) Avoid usage of plastic paper plates, napkins etc.

REUSE:

a)Glass bottles can be reused.

b) Reuse containers, cups, jars, books (can be handed to others when one finishes reading themselves) etc.

RECYCLE

a) Recycled products should be encouraged.

b) Electronic equipments can be recycled.

c) Newspapers can be recycled.

The green colour crystals that the student heated were of ferrous sulphate crystals (FeSO₄). These crystals when heated undergoes decomposition reaction and breaks into ferric oxide, sulphur dioxide and sulphur trioxide (SO₃). The green colour of FeSO₄ crystals thus changes to reddish brown ferric oxide (Fe₂O₃) and then the smell of burning sulphur (SO₂₎ is evolved.

2FeSO₄→ Fe₂O₃ + SO₂ + SO₃ (In presence of heat, the reaction proceeds.)

Physical properties:

a) Acetic acid is soluble in water.

b) Acetic acid has a vinegar like sour smell/odour.

Chemical properties:

a) Acetic acid reacts with sodium bicarbonate to give a brisk effervescence (Carbon dioxide:CO₂) which turns limewater milky, sodium acetate (CH3COONa) and water.

CH₃COOH + NaHCO₃→ CH₃COONa + CO₂ + H₂O

Ca(OH)₂ + CO₂→ CaCO₃ + H₂O

b) It is a weak acid and turns blue litmus red. It dissociates into acetate ion and hydronium ion.

CH₃COOH → CH₃COO^- + H₃O⁺

The KOH (potassium hydroxide) test tube placed within the conical flask absorbs the moisture, oxygen, O₂ in the flask and released CO₂ due to which the level of water rises in the tube due to partial vacuum created by absorbed CO₂. An equal volume of water rises. But here, there was no rise in the level of water maybe because of experimental errors like the cork might not have been properly air-tight or maybe the KOH prepared was not fresh or maybe the germinating seeds were not kept moist etc.

The process observed is budding (asexual reproduction in yeast).

In budding, new organisms are formed as buds/outgrowths from the parent cell/body. The nucleus material of the parent cell splits into two parts and the daughter nuclei enters the daughter cell. The bud detaches itself from the parent yeast cell and develops into an individual daughter yeast cell. The division is asymmetric.

The best choice is option B because the value of angles should the ones which are very common to us and should come handy while calculating the value of refractive index of the slab. Also the value of the distance between the pins should be adequately large so as to avoid error in the calculations.

Standard minimum values for ammeter and voltmeter readings are taken as 0. When not in use, if the readings show anything else then we can conclude that it has zero error. Zero error is how far from zero, the reading is of the instrument. It can either be positive or negative zero error.

Therefore we see that the zero error in the ammeter is negative zero error while that of the voltmeter is positive zero error.

Hence zero error in ammeter: -4milliAmpere

Zero error in voltmeter: +0.4 milliVolt

So, the final reading as seen is:

Ammeter: 34mA

Voltmeter: 3.6 V

Now correcting the reading:

Ammeter: [34-(-4)]mA= 38 mA

Voltmeter:[3.6- (+0.4)]V = 3.2 V

OR

Least Count = smallest value measured by a particular measuring instrument (given 0.05V)

Therefore correct reading: Least count × Number of divisions in the instrument

Here :

(0.05 × 15)V = 0.075 V (the observed reading of voltmeter)

(i) The chemical formula of Plaster of Paris is CaSO₄. 1/2 H₂O, so it has 1/2 molecules of water of crystallisation.

(ii) The chemical formula of Washing soda crystals is Na₂CO₃.10H₂O, so it has 10 molecules of water of crystallisation.

The molecular formula of first two members of homologous series having functional group – Cl are

(i) CH₃Cl (Chloromethane)

(ii) CH₃CH₂Cl (Chloroethane)

A normal eye not able to see clearly the objects placed closer than 25 cm because the ciliary muscles of eyes cannot contract beyond a certain limit so the focal length of the eye lens cannot be decreased below this limit.

Thus an object placed closer than 25cm cannot be seen clearly by a normal eye.

Biotic components mean all the living organisms living on earth. Two biotic components are humans and animals.

Management of forest and wildlife resources is a very challenging task because of the following:

(i) Now-a-days, people are are continuously cutting down trees for the raw materials of the factory.

(ii) People kill animals for making cloth designs and its harming wildlife. So the management of forest and wildlife is a very challenging task.

(i) Combination reactions are those reaction in which two compounds combine to give one product. Combination reactions are always exothermic.

CaO + H₂O → Ca(OH)₂ + Heat

(ii) An oxidising agent is one which oxidises to something and a reducing agent is one which reduces to something.

In this reaction, H₂S is a reducing agent because it is reducing to Cl₂ and Cl₂ is an oxidising agent because it is oxidising to H₂S.

(iii) The phenomenon due to which the taste and smell of oily food changes when kept for a long time in open is known as rancidity. It is prevent by keeping the oily food in airtight container.

(i) The brown colour metal is copper (Cu) and black coloured substance is Copper oxide (CuO).

(ii) (a) When Cu metal is heated in an open china dish then Cu metal gets oxidised

Cu + O₂→ 2CuO

(b) When hydrogen gas is passed over the black substance then CuO gets reduced

CuO + H₂→ Cu + H₂O

We know that alkenes give addition reaction and C₄H₈ is alkene so C₄H₈ will give addition reaction.

CH₃CH₂=CH₂CH₃ + H₂→ CH₃CH₂CH₂CH₃

OR

(i) When Ethyl acetate (CH₃COOC₂H₅) reacts with NaOH, then sodium acetate (CH₃COONa) and ethanol (C₂H₅OH) are formed.

CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

(ii) When acetic acid (CH₃COOH) reacts with NaOH, then sodium acetate (CH₃COONa) and water are formed.

CH₃COOH + NaOH → CH₃COONa + H₂O

(iii) When acetic acid (CH₃COOH) and ethanol (C₂H₅OH) reacts then ethyl acetate (CH₃COOC₂H₅) and water are formed.

CH₃COOH + C₂H₅OH CH₃COOC₂H₅ + H₂O

Adrenalin is a hormone secreted by the adrenal glands in case of danger or emergency. This adrenalin hormone is secreted directly into the blood and is transported to different parts of the body. When this adrenalin hormone secreted in large amounts, it speeds up the heartbeat and hence supplies more oxygen to muscles.

OR

Chemical coordination takes place in animals with the help of hormones. The hormone is the chemical messenger that regulates the processes in living organisms. These hormones secreted by glands.

There are 23 pairs (i.e. 46) of chromosomes present in human beings. In the male, 44 autosomes + XY Allosome and in the female, 44 autosomes + XX Allosome.

The humans have 46 chromosomes, the male has 46 chromosomes, and female has 46 chromosomes when they reproduce sexually then half of their chromosomes will go for progeny i.e. 23 chromosomes from male and 23 chromosomes from female will go for progeny. So progeny get 46 chromosomes totally. Therefore the number of chromosomes in the progeny remains the same as that of the parents.

It is true that natural selection & speciation leads to evolution.

i. The origin of species from pre-existing one leads to speciation of species

ii. Some individuals will be better adapted to the environment than others and will therefore be more likely to breed and pass on their alleles to the next generation, which is called as variation.

iii. This means that each population will begin to evolve different adaptations to suit their environment

iv. With time, this genetic drift, will accumulate different genetic variations leading to evolution of species.

i. The defect is Myopia or near-sightedness.

Explanation: -

As the rays from sun are getting focused onto the paper and burning it, this is indicating that the far point of the eye has shifted from infinity to a few meters and this is clear sign of Myopia as person is able to nearer objects but cannot see far objects.

ii. This defect may arise due to a.) excessive curvature of the eye lens which reduces the focal length of the eye thus the rays coming from infinity get focused much before reaching the retina.

or

b.) elongation of the eyeball which shifts the retina from the focal point of the eye lens thus leading to myopia.

iii.

The point O’ is the actual position of the object and O is the far point of the defected eye the rays from O are getting focused much before reaching the retina due to the aforesaid reason(s).

iv.

The defect is corrected by using a spectacle consisting concave lens of appropriate focal length so as to increase the focal length of the eye lens(the far point has to be shifted) as shown in the diagram.

OR

The person is suffering from myopia, the correcting lens is a concave lens which is of diverging nature. The focal length of the correcting lens can be easily calculated by converting the problem into a simple lens formula problem,

The data given is:

the image distance is, ,

the object distance is, ,

we know that the lens formula is,

, where,

v is the image distance, u is the object distance and f is the focal length of the lens.

Calculations:

So, after substituting the data we have,

So, we get . ,

The power is the reciprocal of the focal length in meters, so

P=-0.625 D.

When we connect high powered devices to a circuit like iron, freeze, fan etc. then it draws large amount of current on same voltage line and heats the wire which is greater than the capacity of that circuit. This is called overloading of the electrical circuit.

Causes due to which overloading may occur in household circuits

(i) Overloading can occur when live wire and the neutral wire come into direct contact.

(ii) Overloading is also caused by connecting too many appliances to a single socket.

Overloading can be prevented by using fuses to the circuit. When current exceeds in circuit then fuses melts and the flow of current stops in the circuit.

(i) We know the magnetic field is stronger near the current carrying conductor and become weaker as we move from the conductor. In case of a current carrying circular loop, the magnetic field is stronger near the wire of circular loop and weaker at the centre of the loop. Due to this, the magnetic field lines appear as straight lines near the centre. And as we move towards the wire of circular loop . The magnetic field lines appear to be diverging so that they can be circular around the wire of the loop.

(ii) The properties of magnetic field lines are

(a) The direction of magnetic field lines is from North to South pole outside the bar magnet and North to South pole inside the magnet.

(b) Magnetic field lines never intersect each other.

Non-conventional sources of energy are those who are setup in that manner so that we can protect our earth and maintain a good eco-friendly atmosphere.

The three reasons are

(i) Rapid increase in population.

(ii)Low supply of fuels.

(iii) Extra use of machines.

(i) The acid is Hydrochloric acid (HCl), and the base is Sodium Chloride (NaOH) which will form Sodium Chloride (NaCl) i.e. common salt.

HCl + NaOH → NaCl + H₂O

It is found naturally in large amounts in sea water.

(ii) Deposits of solid salt found in huge amount in different areas. These large crystals are called rock salt. And rock salt is brown in colour due to impurities.

(iii) When electricity is passed through brine, then sodium hydroxide (NaOH) is formed with the liberation of Hydrogen (H₂) gas at cathode and Chlorine gas (Cl₂) at the anode.

NaCl + H₂O + Electricity → NaOH + H₂ + Cl₂

OR

(i) The chemical name of washing soda is Sodium carbonate decahydrate and its chemical formula is Na₂CO₃.10H₂O.

(ii) (a) First sodium hydrogen carbonate prepared from sodium chloride by reaction of ammonia and carbon dioxide.

NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ + NH₄Cl

(b) And then sodium carbonate is obtained by heating sodium hydrogen carbonate.

NaHCO₃→ Na₂CO₃ + CO₂ + H₂O

(c) Recrystallization of sodium carbonate gives washing soda.

Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O

(iii) It is basic salt because it is the salt of strong base and weak acid. It is used as cleaning agent.

(i) Since the element is placed in 2^nd group and 3^rd period of the periodic table then this means the element has 2 valence electrons and 3 shells. So it is Magnesium (Mg).

(ii) Its electronic configuration is 2, 8, 2.

(iii) The chemical equation when it burns in the presence of air is

2Mg + O₂→ 2MgO

(iv) The balanced equation when this oxide is dissolved in water is

MgO + H₂O → Mg(OH)₂

(v)

(i) The sequence of events that occur during the process of photosynthesis are:

(a) Adsorption of light energy by the chlorophyll pigment.

(b) Conversion of light energy into chemical energy.

(c) Splitting of water molecules into hydrogen and oxygen.

(d) Formation of carbohydrates from CO₂ gas.

(ii) There are three types of blood vessels

• Arteries

• Veins

• Capillaries

(i) A. Ovary- They produce oocytes (eggs) for fertilisation, and they produce the reproductive hormones oestrogen and progesterone.

B. Uterus- The function of the uterus is to accept a fertilized ovum which passes through the utero-tubal junction from the fallopian tube (uterine tube).

C. Fallopian tube- The function of the fallopian tube is to transport the egg from the ovary to the uterus.

(ii) The placenta is a disc-shaped structure formed on the uterine wall just before the implantation of the gastrulocyte (embryo). The functions of placenta are:

(a) It helps in transporting substances such as oxygen, carbon dioxide, glucose, amino acids, fatty acids and glycerol, antibodies and waste products, etc.

(b) It transforms as an endocrine gland secreting progesterone and oxytocin.

(c) It provides attachment to the embryo and nourishment.

i. A. Pole-The center of the reflecting surface of a spherical mirror is a point called the pole. It lies on the surface of the mirror. The pole is usually represented by the letter P.

B. Center of curvature-The reflecting surface of a spherical mirror forms a part of a sphere. This sphere has a center. This point is called the center of curvature of the spherical mirror. It is represented by the letter C.

C. Principle Axis- The imaginary line which connects the pole to the center of curvature is called the principle axis.

D. Principal Focus- A number of rays parallel to the principal axis are falling on a spherical, reflected rays are all meeting/intersecting (or intersects when extended backwards and/or forward) at a point on the principal axis of the mirror. This point is called the principal focus of the concave mirror

ii. A. Concave mirror

B. Convex Mirror

i. The mirror is concave mirror as a concave mirror makes a magnified virtual image of the object when it is placed between the focus and pole of the mirror. The image is virtual, erect and magnified.

OR Part

i.

ii.

The lens formula is

where v is the image distance, u is the object distance, f is the focal length (both as per the sign convention). For the above situation the formula can be written as,

iii. The data given is:

the object distance is, ,

the magnification is, m,

we know that the magnification for lens is given by the formula ,

, where,

V is the image distance, u is the object distance, h_o is the object size and h_iis the image size.

Calculations:

So, after substituting the data we have,

So, we get .

So using the lens formula we can obtain the focal length of the lens

, where the symbols have the usual meanings.

Substituting the given and founded data, we can write,

So, f = 10 cm

We know that power of a lens is the reciprocal of the focal length in metes,

.

P = 10 D.

(i) A. If the resistors are connected in series then equivalent resistance is

R = R₁ + R₂

= 10 + 10

= 20 Ω

Power consumed (P₁) =

=

= 1.8 Watt

B. If the resistors are connected in series then equivalent resistance is

R =

=

_{= 5Ω}

Power consumed (P₂) =

Ratio =

(ii)

A.

When an aqueous solution of barium chloride reacts to an aqueous solution of sodium sulphate then precipitate of barium sulphate is formed along with sodium chloride because barium (Ba) is more reactive than Sodium (Na) so it will displaced to sodium from sodium sulphate. It is double displacement reaction.

BaCl₂ + Na₂SO₄ BaSO₄ + 2NaCl

The zinc sulphate solution is colourless, when a copper strip is placed inside it, there is no colour change observed as zinc is more reactive than the copper as per the activity series.

Cu(s) + ZnSO₄ (aq.)No reaction.

The student has to get the peel from the lower surface of the leaf.

OR

He will observe the rise of water level in the beaker because vacuum is created due to adsorption of CO₂ by KOH.

Diagram II is not correct because nuclei of bud and parent cell do not connect to each other. Their nuclei are always separated.

For light going from air to glass at point E

μ_a sin i = μ_g sin r ……. (1)

For light going from glass to air at point F

μ_g sin r = μ_a sin e ……. (2)

From (1) and (2) we can say that i = e

Case 1. When ∠i = 30^o

μ_a sin i = μ_g sin r

Sin r = 1/3

r = 19.26^o

And i = e

So e = 30^o

Case 2. When ∠i = 45^o

μ_a sin i = μ_g sin r

1×sin45 = 3/2×sin r

1/√2 = 3/2×sin r

Sin r = √2/3

r = 28.09^o

And i = e

So e = 45^o

Equivalent resistance = 3 + 6

= 9Ω

Maximum voltage to be measured = 4.5

Maximum current to be measured = 4.5/9

= 0.5 A

These requirements of measuring this current and voltage are fulfilled by ammeter A₂ and voltmeter V₂ and these two instruments have smaller least counts 0.05 A and 0.1 V so these are more accurate. Hence the best combination of ammeter and voltmeter is A₂ and V₂.

Tap water conducts electricity whereas distilled water does not because:

i. Tap water has certain salts and chemicals dissolved in it.

ii. When electricity is passed through tap water, these salts and chemicals change into ions.

iii. These ions are responsible for the conduction of electricity in tap water.

iv. Whereas distilled water has no such salts and chemicals dissolved in it.

v. When electricity is passed through distilled water, no ions are formed. Thus, no conduction of electricity in distilled water.

Hence, due to the presence of dissolved salts in tap water, the tap water conducts electricity and distilled water due to the absence of these salts do not conduct electricity.

An organic compound burns with a sooty flame, it is an unsaturated compound.

Explanation:

i. When an unsaturated compound is burned it will give a yellow flame with lots of smoke.

ii. This is the sooty flame.

iii. This happens due to incomplete combustion.

iv. When the compound is burned in a limited supply of oxygen, it will release CO (Carbon monoxide) in place of CO₂ resulting in incomplete combustion.

Hence, unsaturated compound gives sooty flame due to incomplete combustion.

Planets do not twinkle because:

i. Planets are very close to the earth.

ii. Hence, they cannot be seen as point sized sources.

iii. The light coming from the planets do not vary. Thus, causing no fluctuation in the position of planet.

iv. If we consider planets as a group of point-sized particle, then the light entering our eye from the individual source will become zero.

v. Causing no twinkling effect on the planet.

Hence, planets do not twinkle due to their small distance from the earth.

***note: when the object sometimes becomes brighter and sometimes fainter, this is the twinkling effect. It is caused by the fluctuation of the amount of light entering our eye from the object***

The biodegradable items from the list are:

• Old clothes

• Wilted flowers

• Pencil shavings

• Vegetable peels

Explanation:

i. Polythene bags are made of plastic. These cannot be broken down by any microorganism. Hence, they are non-biodegradable

ii. Old clothes are made of cotton and cotton being a natural product is biodegradable which means it breaks down into simpler products.

iii. Wilted flowers are also natural products fallen from the plants/trees making it a biodegradable item.

iv. Pencil shaving is made from wood which is also a natural product. It is hence biodegradable.

v. Glass bangles made up of glass remains intact in the environment and do not decompose. Hence, they are non-biodegradable.

vi. The bronze statue made up of bronze corrodes very slowly and cannot be decomposed. Hence, the bronze statue is a non-biodegradable item.

vii. Vegetable peels are natural products obtained from the plants.

Hence, old clothes, wilted flowers, pencil shaving and vegetable peels are biodegradable because they are broken down to simple products.

Two benefits of Chipko Andolan:

1. The local people were able to use the products of the forest and fulfil their needs which were earlier stopped by the government.

2. The Chipko Andolan also helped in correct management of the forest and their products.

• When the villagers protected the trees by hugging them, the government was forced to rethink about the correct use of forest and forest product.

i. The substance X is Sodium Carbonate, and the formula of Sodium Carbonate is Na₂CO_3.

ii. The reaction of sodium carbonate with water is given below:

Na₂CO₃ + 10H₂O → Na₂CO_3.10H₂O

Explanation:

i. Washing soda is another chemical that can be obtained from sodium chloride.

ii. Sodium carbonate is obtained by heating baking soda (NaHCO₃).

iii. When sodium carbonate reacts with water, it forms Washing Soda.

iv. The chemical formula of washing soda is Na₂CO_3.10H₂O.

i. The metal oxides that dissolve in water are alkali metals. The solution of metal oxides in water is called as a diluted solution or alkaline solution.

Explanation:

• Metal oxides react with water to form metal hydroxides.

• Eg: Na₂O + H₂0 → NaOH

• Metal hydroxide or the bases that are soluble in water are called alkali and they generate hydroxide ions (OH^-)

• Example: NaOH + H2O → Na ⁺ + OH^-

ii. At ordinary temperature, the surface of metals such as magnesium, aluminium and zinc is covered with a thin layer. The thin layer is the oxide layer.

Importance of oxide layer:

• The oxide layer covers the metal fully and makes it less reactive.

• This covering is a way of protecting the metal from corrosion.

• Hence, with this layer the metal do not corrodes and can remain in its original form.

iii. Some alkali metals such as lithium, sodium, potassium can be cut with a knife. These metals are so soft that they can be cut with a knife easily.

Carbon cannot form C^{4 +} cations nor C^4- anions. The reasons are:

i. The atomic number of carbon is 6. According to electronic configuration, it has 4 electrons in its valence shell.

ii. If carbon will form C^4- anions, it has to gain four electrons. In this case, the carbon will have 6 protons and 10 electrons making it difficult for the nucleus to hold them. Thus, carbon does not form C^4- anions.

iii. If carbon will form a C^{4 +} cation, it has to lose 4 electrons. A very large amount of energy will be used to remove 4 electrons from an atom. Also then the carbon will have 6 protons with just 2 electrons again making it difficult for the nucleus.

iv. Thus, instead of losing or gaining four electrons, Carbon shares it electrons forming covalent bond.

i. The first diagram shows the response of plant parts towards the light. This is known as phototropism.

• The light acts as a stimulus.

• The shoot shows a positive response to the stimulus, i.e., it bends towards the sunlight.

• The root shows negative response to the stimulus, i.e., it bends away from the sunlight.

ii. a) The two parts in the diagram will be labelled as:

1. Spinal cord (Central Nervous System)

2. Effector (muscle in the arm)

b) The suitable caption or the heading for the diagram is Reflex Arc.

***note: the reflex arc is the pathway by which reflex action is completed***

OR

Difference between the manner in which movement takes place in a sensitive plant and the movement in our legs is given in the table below:

i. When green stemmed (GG) is crossed with purple stemmed (gg) tomato plant, the F₁ progeny will have green stemmed tomato plants (Gg). The diagram below shows the cross in the form of punette square.

The genotype will be Gg in case of all the plants making the plant phenotypically green stemmed.

ii. When the F₁ (Gg) plants will be self-pollinated the result will be:

When we study the self-pollination of F₁ plants in the above figure we will observe that only one plant has both recessive alleles (gg).

Hence, the percentage of purple-stemmed plants when F₁ is self-pollinated is 25%.

Explanation: the Purple stem is a recessive trait, and it will be able to express itself in homozygous conditions only. When progeny has gg then the plant will have purple stem

iii. The genotype GG represents stemmed green plant with both dominant alleles. The genotype Gg represents green stemmed plants with one allele being dominant (G) over the other allele (g, recessive)

Hence, on studying the above figure again, we observe that only 1 plant has GG genotype whereas the plants having Gg genotype are 2.

The ratio of GG and Gg in F₂ progeny is 1:2.

I. When a pure tall pea plant (TT) is crossed with a pure dwarf pea plant (tt), the result of F1 progeny is given in the diagram below:

• In the cross above the allele (T) becomes dominant over the other allele (t) making it recessive.

• When the dominant allele T from the tall pea plant is paired with the recessive allele t of the dwarf pea plant, the result in the genotype is Tt.

• In Tt, T is dominant over the t.

Hence, in F1 generation the dwarf traits become recessive making tall trait as dominant, and all the plants in the progeny will be tall.

II. When F1 generation is self-fertilized the cross obtained is given below:

When F1 generation is self-fertilized the progeny of F2 is both tall and dwarf due to the following reason:

• The genotype of the parents of F1 generation is Tt, which means dominant as well as recessive both traits are present in the allele. The plant will be tall as tallness is a dominant trait.

• When T from 1^st tall pea plant is crossed with T from the 2^nd tall pea plant, the genotype of the progeny is TT, having both the dominant allele, resulting in homozygous condition. Hence, it is without doubt phenotypically tall.

• When T (from the 1^st plant) is crossed with t (from the 2^nd plant), the result is Tt, resulting in heterozygous conditions. In such case, only dominant traits can express, making the plant tall.

• When t (from the 1^st plant) is crossed with T (from the 2^nd plant), it will again form a heterozygous condition, making the plant tall.

• When t (from the 1^st plant) is crossed with t (from the 2^nd plant), the result in the genotype is tt. The recessive allele will be able to express itself only in homozygous condition. Hence, because the allele has homozygous tt conditions, the plant will be dwarf.

Hence, due to the presence of homozygous alleles (TT, tt) and heterozygous alleles (Tt, Tt), the progeny of the F2 generation will be both tall and dwarf.

i. The white light falling on a glass prism splits into 7 colour in the following sequence:

1. R – red

2. O – orange

3. Y – yellow

4. G – green

5. B – blue

6. I – indigo

7. V - violet

The position marked on number 3^rd is YELLOW. Yellow is not the colour of the sky.

Similarly, the position marked on number 5^th is BLUE. Blue is not the colour of the core of the hard-boiled egg.

Hence, the statement made by the student of no 3^rd as the colour of sky and no. 5^th as the colour of core of hard-boiled egg is INCORRECT.

ii. The colour of potassium permanganate is violet (purple), and the colour of danger sign is red.

a) The position corresponds closely to the colour of the solution of potassium permanganate is 7^th (violet colour)

b) The position corresponds closely to the colour of danger or stops light signal is 1^st (red colour).

‘OR’

FORMATION OF RAINBOW IN THE SKY:

1. A rainbow is a combination of 7 colours which is normally seen after rain.

2. A rainbow is formed naturally in the sky after rain shower opposite to the position of the sun.

3. Three different phenomena are involved in the formation of the rainbow: refraction, dispersion and reflection.

4. Refraction is a phenomenon in which the light turns or bends when it is passed from one medium to another having different optical densities.

5. Dispersion is the phenomenon of scattering of light into its seven components (colours).

6. Reflection is the phenomenon in which the light is sent or thrown back by a surface without absorbing it.

7. A rainbow appears by scattering of sunlight.

8. The water droplets act as tiny prisms which lead to scattering of light.

9. The prism refracts and scatters the sunlight.

10. This scattered light is then reflected by the water droplets.

11. When the light comes out of the water droplet, it is again bent due to refraction.

12. Due to this dispersion and reflection, different colours reach the observer’s eye making it a rainbow.

13. The formation of the rainbow is given in the diagram below:

Rainbow formation

Electromagnetic: The word electromagnetic means the field produced by electrically charged objects. It involves the interaction between electrically charged particles.

Induction: The word induction means the process in which an electric or magnetic field is generated in the conductor when it is brought near an object with an electric field or changing magnetic field.

These two terms on combination form Electromagnetic Induction. It is defined as the production of electric current in the conductor when it is brought near the changing magnetic field.

In more simple terms electromagnetic induction can be explained as the process by which the change in the magnetic field in a conductor induces a current in another conductor.

Factors on which the value of induced current produced in a circuit depends are:

1. Nature of magnet: The value of induced current produced depends on the nature of magnet used. Greater the power of magnet, greater will be the induced current production.

2. A number of turns in a coil: More the number of turns in the coil, greater will be the amount of current produced. Suppose there are 10 turns in the coil, then the induced current produced is 10 times.

The practical application of electromagnetic induction in everyday life is Electric Generator.

It works on the principle of electromagnetic induction.

Electromagnetic: The word electromagnetic means the field produced by electrically charged objects. It involves the interaction between electrically charged particles.

Induction: The word induction means the process in which an electric or magnetic field is generated in the conductor when it is brought near an object with an electric field or changing magnetic field.

These two terms on combination form Electromagnetic Induction. It is defined as the production of electric current in the conductor when it is brought near the changing magnetic field.

In more simple terms electromagnetic induction can be explained as the process by which the change in the magnetic field in a conductor induces a current in another conductor.

Factors on which the value of induced current produced in a circuit depends are:

1. Nature of magnet: The value of induced current produced depends on the nature of magnet used. Greater the power of magnet, greater will be the induced current production.

2. A number of turns in a coil: More the number of turns in the coil, greater will be the amount of current produced. Suppose there are 10 turns in the coil, then the induced current produced is 10 times.

The practical application of electromagnetic induction in everyday life is an Electric Generator. It works on the principle of electromagnetic induction.

ADVANTAGES OF USING SOLAR COOKER:

1. No harm to Environment: The solar cooker use solar energy to complete its work. There are no chemicals or smoke released that is harmful to the environment. In short, it is pollution free.

2. Safe to use: The solar cooker is the safest appliance to be used. There is no fear of gas leakage, fire, burning of wood, burning of food etc.

3. No electricity: The solar cooker is totally dependent on solar energy. There is no requirement of electricity for the solar cooker to work.

DISADVANTAGES OF USING SOLAR COOKER:

1. Climatic conditions: Solar cooker uses solar energy to work efficiently. In the absence of sunlight during winter and rainy season, the cooker cannot function.

2. Time-consuming: The time required to cook in a solar cooker is greater than the time required to cook on the gas stove. Hence, solar cookers are time consuming.

Solar cookers are direct dependent on sunlight (solar energy) to work. Hence, a solar cooker cannot be used in places where no or limited sunlight is available.

The places with no sunlight would have limited solar cooker utility.

i. The by product of chloroalkali process is NaOH. NaOH when kept in open air absorbs moisture and turns sticky. Hence, X is NaOH.

• When NaOH is treated with strong acid for example HCl, then neutralisation reaction will occur.

• Neutralisation is a reaction between an acid and a base to give salts and water.

• NaOH being strong base and HCl being strong acid reacts with each other to produce Sodium Chloride (NaCl). This is neutralisation reaction.

The balanced chemical equation is given below:

NaOH + HCl →NaCl + H₂O

***note: chloroalkali process is an industrial process in which electrolysis of sodium chloride is done in order to obtain chlorine and sodium hydroxide***

ii. X which is NaOH can be stored in Aluminium container.

Explanation: If we see the reactivity series, we will observe that Sodium is placed above Aluminium which means Sodium is more reactive than Aluminium. Hence, no reaction will take place between NaOH and Al.

‘OR’

i. Rain water conducts electricity whereas distilled water does not because:

• Rain water has certain salts and chemicals dissolved in it.

• When electricity is passed through rain water, the salts and chemicals change into ions.

• These ions are responsible for the conduction of electricity in tap water.

• Whereas distilled water has no such salts and chemicals dissolved in it.

• When electricity is passed through distilled water, no ions are formed. Thus, no conduction of electricity in distilled water.

Hence, due to the presence of dissolved salts in rain water, the rain water conducts electricity and distilled water due to the absence of these salts do not conduct electricity.

ii. We feel burning sensation in the stomach when we overeat because:

• The walls of the stomach release acid HCl.

• This acid is used in the digestion process.

• When the food enters the stomach, this acid is released so that digestion can take place.

• Larger the amount of food, the larger is the acid released.

Hence, due to the formation of HCl in the stomach, we feel a burning sensation.

iii. Tarnished copper vessel regains it shine when rubbed with lemon because:

• Tarnishing of copper vessel takes place because a copper oxide layer is formed on the surface of the vessel.

• The copper oxide is basic in nature.

• When lemon which is acid is rubbed on copper oxide which is a base, neutralisation reaction takes place.

• This reaction nullifies the effect of copper oxide, and the vessel gains its original shine.

Hence, due to neutralisation, the tarnished copper vessel gains its original shine when rubbed with lemon.

iv. The crystals of washing soda change to a white powder on exposure to air because:

• The formula of washing soda is Na₂CO_3.10H₂O.

• The washing soda has 10 molecules of water.

• When it is exposed to air, the crystals of washing soda lose the water of crystallisation.

• This loss of water turns the crystal of washing soda to a white powder.

Hence, due to the loss of water from washing soda, the crystal turns to white powder.

v. An aqueous solution of sodium chloride is neutral, but an aqueous solution of sodium carbonate is basic because:

• Sodium chloride is formed as a result of neutralisation of sodium hydroxide and hydrochloric acid.

• Sodium chloride is a salt containing a strong acid HCl and a strong base NaOH.

• Hence, the aqueous solution of sodium chloride is neutral.

• Sodium carbonate, on the other hand, is a salt of weak acid and a strong base.

• When it is added in water, the amount and power of OH^- ions is greater than H ⁺ ions.

• Hence, the aqueous solution of sodium carbonate is basic.

i. Noble Gas: G; Halogen: F

Explanation:

• The last group elements (18^th) are known as noble gas because their valence electron is filled.

• Hence, G because of electronic configuration 2, 8 is a noble gas.

• The second last group elements (17^th) are known as halogens because they need only one electron to completely fill their valence electron shell.

• Hence, F due to electronic configuration 2, 7 is the halogen.

ii. The most active element in the 3^rd period is B.

Explanation: The atomic number of B is 11. Hence, the electronic configuration of B is 2, 8, 1. It has only one electron in its valence shell. It loses its one electron very easily and forms bonds with many elements becoming the most reactive element.

iii. The most electronegative element of the 3^rd group is F.

Explanation: The electronic configuration of F (17) is 2,8,7. It needs 1 electron to complete its shell. Instead of losing the 7 electrons, it gains 1 electron. Hence, it is the most electronegative element of group 3^rd.

***note: electronegativity is defined as the tendency to gain electrons***

iv. In between B and F, the ionic bond will be formed.

Explanation: The E.C. of B (11) is 2,8,1 and E.C. of F (17) is 2,8,7. B will lose its one electron to form B ⁺ cation and F will gain this one electron from B to complete its shell and become F^- anion. Hence, the bond between B and F will be an ionic bond as ion formation takes place.

v. The nature of oxides form by C (12) will be basic.

Explanation: The EC of C (12) is 2,8,2. It belongs to group 2. Hence, C is a metal and because of a general rule metal oxides are always basic.

1) The leaves of a plant started getting wilted, the tissue that might have blocked is Xylem. Wilting generally means drooping or falling due to lack of water. Xylem is responsible for water transportation, hence, it might have been blocked.

Role of xylem in plants:

i. It is a vascular tissue that helps in transportation.

ii. The xylem is responsible for the transport of water and minerals in the plants.

iii. It transports water from roots to the stem. Hence, its flow is only in one direction (unidirectional).

iv. Xylem also provides mechanical support to the plant.

v. The xylem has four different elements: tracheids, vessels, xylem fibres and xylem parenchyma.

vi. The xylem parenchyma stores food material in the form of starch.

2) Opening and closing of stomata:

• The opening and closing of stomata depend upon the guard cells.

• The guard cells are bean-shaped cells will allow as well as prevents the entry of water.

• When the water enters the guard cells, they swell. The swelling of guard cells results in the opening of the stomatal pore (also known as stomatal aperture).

• When the water flows out of the guard cells, the guard cells shrink, and the pore closes.

• The open and closed stomata are shown in the diagram below:

3) The physical phenomenon by which the exchange of gasses occur between plant body and atmosphere Respiration.

During respiration the plant uses O₂ and form energy and CO₂, this carbon dioxide at night is released in the atmosphere whereas during day time this carbon dioxide is used in the process of photosynthesis to form food.

i. The organ that produces sperms as well as secretes a hormone is testis.

The hormone released by testis is testosterone.

Functions of testosterone:

• It is a male sex hormone.

• It helps in the formation of sperms which are male gametes.

• It brings changes in the males at the time of puberty.

• Changes like the growth of body hair, change in voice, enlargement of penis etc. are brought by the release of the hormone testosterone.

ii. The part of a human female reproductive system where fertilization occurs is a Fallopian tube.

• The female gamete egg is formed in the ovaries.

• The ovary releases an egg every month.

• This egg is transported in the fallopian tube where it meets with the male gamete ‘sperm’, and fertilization takes place.

Hence, fertilization takes place in the fallopian tube.

iii. The developing embryo gets nourishment from the mother body through special tissue called placenta.

Explanation:

• The placenta is a special connection of tissue formed between mother and the foetus.

• The placenta is a disc-like structure attached in the uterine wall from one side and the foetus body from another side.

• The food from the mother body is passed into the foetus through this placenta.

• The waste material that foetus develops is also removed by the foetus in the placenta n it reaches the mother and hence is excreted.

When an object is placed at 2F₁ of a convex lens, image is formed at the opposite 2F₂ point. For this mirror 2F = 30 cm, we get f = + 15 cm.

ii. Clearly the observation no. 6 is wrong as the image distance should have been negative but it is given that it is positive.

This is so because a convex lens produces a virtual image when the object is between focus and the optical centre.

iii. Magnification is given by,

OR

i. The two rays are originating from the top of the object. One is passing through the spherical centre of the mirror and the other ray is passing through the pole of the mirror.

ii. Magnification is given by,

So the distance between the screen and the object is 60-20 = 40 cm.

(i) The electric power consumed by a device may be calculated by using either of the two expressions P = I²R or P = V²/R. The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. The seemingly different dependence of P on R in these expressions be explained by the fact that the if in the first expression , if resistance increases the current decreases as per the ohm’s law and thus the power consumed if effectively given by P = IV. In the second expression ,if resistance increases the voltage increases as per the ohm’s law and again the effective power is given by the expression P = VI.

(ii) (a) Tungsten is used almost exclusively for the filament of electric lamps due to the following reasons:

• High melting point: The high melting point of tungsten ensures that it does not melt easily on high temperature.

• Tensile strength: The tungsten has the greatest tensile strength. Great tensile strength ensures that they does not break under tension.

• Vapour pressure: The tungsten has a lowest vapour pressure. The vapour pressure is the indication of the evaporation rate. Lower the vapour pressure, lower is the boiling point.

(b) Copper and aluminium wires are used for electricity transmission due to following reason:

• Copper and aluminium have very less resistivity.

• Lower the resistivity, easier the flow of electricity.

Hence, copper and aluminium wires are used for electricity transmission because of their low resistivity.

***note: resistivity is defined as power of a material to resist or oppose the flow of electricity through it.

On heating the ferrous sulphate crystals loses water and becomes anhydrous ferrous sulphate. It also changes its colour from green to white.

FeSO₄.7H₂O→FeSO₄ + 7H₂O

If we further heat ferrous sulphate then decomposition occurs and ferric oxide, sulphur dioxide and sulphur trioxide are formed as a result of decomposition.

FeSO₄→Fe₂O₃ + SO₂ + SO₃

• Iron is more reactive than copper.

• So, when iron fillings are added to copper sulphate solution, iron displaces copper from copper sulphate and takes the place of copper forming ferrous sulphate.

• Hence, the displacement reaction takes place.

• The formation of ferrous sulphate leads to the change in colour.

• The blue colour of solution changes to pale green colour.

• The layer becomes brown in colour.

Red as well as blue light influences the opening of stomata. The maximum absorption of light takes place in blue and red region by the chlorophyll.

Binary fission in Amoeba:

Binary fission is a mode of asexual reproduction in which only one parent is involved. In binary fission the parent body divides into two daughter cells. It is more convenient to say that the parent body changes into the daughter cells.

Budding in Yeast:

In budding, a small outgrowth is formed on the parent body, known as a bud. This bud on favourable conditions germinates and is detached from the parent body to form a new individual. Hence, in budding the whole parent body is not converted to the new individual but just a part of it.

Budding in yeast

i. The type of the lens used in the figure is a convex lens.

ii. The image is real, inverted and magnified.

iii. When the object is placed at the twice distance of focal length then the magnification produced is -1.

OR

When obtaining an image of an object (if the object is distant), in order to get a sharp image, the mirror should be moved towards the screen in order to get a sharp image. This is so because as the mirror is brought near to the screen, the screen comes near the focus of the mirror thus a sharp image is obtained.

The graph is given below:

The current (I) is marked on the X axis and the potential difference (V) on the Y axis.

Explanation: According to Ohm's law, the electric current flowing through the metallic wire is directly proportional to the potential difference V across its ends when the temperature remains the same.

V I

V/I = constant

= R

Therefore, V = IR

R is the constant and is known as resistance.

This shows that greater the potential difference, greater is the flow of current. Similarly, lower the V, lower is the value of I.

During summers, the temperature is high. As a result of high temperature, the Lactobacillus bacteria present in the milk increases in number, which produces more lactic acid. More lactic acid decreased the pH of milk. Because of this reason, milkman usually adds a very small amount of baking soda to fresh milk to increase the pH of the milk as baking soda is a base and neutralise the pH of milk in summers.

The functional group present in the given compound is -COOH, i.e. the Carboxylic acid group.

The IUPAC name of the above given compond is Propanoic acid.

The structure of the compound is shown below:

(i) When the person is able to view objects placed at close distances clearly then the medical condition diagnosed will be myopia. Myopia is also known as short-sightedness or near-sightedness.

In a normal eye, the light focuses on the retina. With myopia, the eye is too long and focuses light in front of the retina, thus forming a blurred image.

(ii) To correct Myopia i.e. short -sightedness, corrective lenses should be used.

To increase the range of vision from 25cm to infinity a concave lens should be used in front of the eye lens which will diverge the rays coming from infinity, and the eye lens will converge the rays and thus forming the image on retina and not in front of it.

(Correction of eye affected by myopia)

An ecosystem is a community of living organisms together with the non-living components of the environment like air, water and mineral soil, combining as a system. Ecosystems can be of any size.

There are two main components of an ecosystem which are the biotic components and the abiotic components.

Biotic Components of Ecosystem

The living components of an ecosystem are called the biotic components. It includes plants, animals, as well as microscopic organisms like fungi and bacteria also. These biotic components can be further classified into producers, consumers and decomposers, based on the energy requirement source.

Abiotic Components of Ecosystem

Abiotic components are the non-living factors, i.e., physical or the chemical factors that act upon the living organisms. These are also known as ecological factors. These factors include water pH, sunlight, water depth, salinity, available nutrients/minerals and dissolved oxygen in the water body, soil, soil types, temperature, rain, altitude, wind, etc.