Is Matter Around Us Pure

Colloids are stable heterogeneous mixture that does not settle down when left undisturbed. Colloidal particles are too small to be visible to the naked eye but are large enough to scatter a beam of light that passes through it and makes the path visible, phenomenon known as Tyndall effect.

Crystallization is the method of choice for obtaining pure Copper sulphate from an impure sample. In this process the sample is dissolved in minimum amount of water and impurities are filtered out. Then the water is evaporated and pure sample is obtained.

iii) Milk will show Tyndall effect as milk is a colloid.

Common salt solution and copper sulphate solution does not show Tyndall effect as they are less than 1nm in diameter and cannot be seen by naked eye. Due to its small particle size, they do not scatter a beam of light passing through the solution.

A pure substance is made of constituent particles that are same in their chemical structure. They have a fixed melting and boiling point and as such the purity can be tested by comparing the melting point of the impure substance with a pure standard.

Particles of a colloidal solution can be separated by centrifugation. The process employs the principle that particles that are dense settle at the bottom whereas the lighter particles stay at the top when spun rapidly.

On heating the blue ink which is a mixture of water (volatile) and dye (non-volatile), the solvent water got evaporated from the watch glass leaving the solute, dye. The process involved is evaporation of water.

The residue left on the watch glass is the solute, dye. Due to heating of the ink the water, solvent in the ink got evaporated leaving behind the dye, the solute.

A pure substance is made of constituent particles that are the same in their chemical structure whereas mixtures consist of more than one kind of pure form of matter. Thus, ink is a mixture since it is made of two substances i.e. water (solute) and dye (solvent).

Blue ink consists of two or more colour. Separation of individual colour components can be done through the use of chromatography. In this technique, the component that is more soluble with the solvent moves faster as compared with the less soluble ones and as such gets separated.

Pure sugar can be obtained from sugar solution by the process of crystallization. It involves heating which leads to evaporation of water to make the solution saturated. The saturated solution when left undisturbed convert to pure crystals of the sugar.

The process of crystallization involves dissolving the impure substance in a minimum amount of water in a china dish. It is followed by filtration of the same, and finally evaporating the water to obtain the saturated solution. The saturated solution when left undisturbed convert to pure crystals of the substance. Thus, one observes crystals of pure substance in the china dish.

The crystals look similar and as such, they are pure since the impurity has already been removed in the filtration step where prior to evaporation the solution was filtered to remove any impurity.

The solution obtained after dissolving the substance in a minimum amount of water is first filtered. Then, the water in the solution is evaporated to obtain a saturated solution. The solution is left undisturbed, covered with a filter paper to cool slowly, which leads to the formation of crystals of the substance.

During the process of crystallization the solution is heated after filtering it as heating evaporates the water that is used to dissolve the impure substance. It does coverts the unsaturated solution into a saturated one.

Crystallization is the most commonly used method for the process of purification of solids. In this method, impure substances are dissolved in minimum amount of water and then filtered. The filtered solution is then heated to obtain a saturated solution. It is then cooled overnight to obtain crystals of the substance.

Sodium is a metal because it is a good conductor of electricity, malleable and ductile. It can lose electron easily from the valence shell whereas carbon is a bad conductor of electricity not lustrous or malleable. It does not lose electrons easily.

Metalloids are substances that show the properties of both metal and non-metal. Examples of metalloids include boron, silicon, germanium etc. They are situated between the metals and the nonmetals in the periodic table.

Man-made elements are elements that do not occur naturally but are produced in the laboratory. There are 24 man-made elements that were synthesized in the laboratory and find place in the periodic table. They are unstable and radioactive in nature. Examples include Dermstadtium, Technetium etc.

Bromine is a nonmetal which is a liquid at room temperature. It is a red fuming brown liquid at room temperature. Its electrons are spread away from the nucleus and so it exists in the liquid state.

Mercury is a metal which is liquid at room temperature. It has the lowest melting point among metals and as such is a liquid at room temperature. It is silvery white in colour.

Hydrogen gas is a colourless, odourless gas and is also combustible whereas hydrogen sulphide, H₂S is a colourless gas with the smell of rotten eggs. It is produced by bacteria.

(a) Aerosol: Fog

Fog is an aerosol which has liquid as the disperged phase and gas as the dispersing medium.

(b) Solution

Lemonade water

In lemonade water, the sugar and the salt are evenly distributed giving rise to a homogeneous mixture of the same.

(a) Quick lime: Quick lime is calcium oxide (CaO) and the elements present are calcium and oxygen.

(b) Hydrogen bromide: Hydrogen bromide (HBr) consists of elements hydrogen and bromine.

(c) Baking powder: Baking powder or sodium bicarbonate (NaHCo₃) consists of elements sodium, hydrogen, carbon and oxygen.

(d) Potassium sulphate: Potassium sulphate (K₂SO₄) consists of elements potassium, sulphur and oxygen.

Given:
Volume of H₂SO₄ = 10ml

Density of H₂SO₄ = 1.84 g/ml

Now, we know,

Mass = Density × Volume

= (10 ml × 1.84 g/ml) g

= 18.4g

Total volume of the solution= (10+90) ml

= 100ml

Mass by volume percentage

= 18.4 %

Hence, the mass by volume percentage of the solution is 18.4 %

Emulsions are colloids where both dispersed phase and dispersing phase are liquid. In case of gels dispersed phase is liquid and dispersing medium is solid.

Example of emulsion is milk and example of gel is jelly.

(i) Homogeneity: Soda water is a solution and as such it can be differentiated based on the property of homogeneity.

(ii) Filtration: Muddy water is a heterogeneous mixture and can be separated by filtration

iii) Tyndall effect: Milk is a colloid and exhibits the property of Tyndall effect

(a) The different pigments from an extract of flower petals: Chromatography can be applied for separation of the components from a mixture.

(b) Butter from curd: Centrifugation can be applied for the separation of butter from curd. The principle is that denser particles are forced to the bottom and lighter particles stay at the top.

(c) Oil from water: For separation of oil from water, the mixture is poured in a separating funnel and is let to stand undisturbed, the water and oils separate into layers the stop clock of the funnel is opened and water is poured out from the lower layer separating the two.

Since oil and water differ in their densities they separate based on it.

(d) Tea leaves from tea: Filtration is the process used to separate tea leaves from tea.

(e) Iron pins from sand: Magnetic property of iron is used to separate iron pins from sand. Irons pins get attracted to the magnet and as such get separated from the sand.

(f) Wheat grains from husk: Wheat grains can be separated from husk by the process of winnowing.

(g) Fine mud particles floating in water: Centrifugation can be applied for separation of mud particles from water.

A solution is said to be saturated if it has with the maximum possible amount of solute that it can dissolve whereas a solution is said to be unsaturated if a solution contains less than the maximum amount of solute. Thus, to test if a solution is saturated or not we need to add sodium chloride, if it dissolves then it is not saturated and if it does not dissolve then its unsaturated.

The solubility of a saturated solution can be increased by increasing the temperature.

(a) 1. Colloids are a heterogeneous mixture consisting of two phases dispersed phase and dispersing phase.

2. Its size is too small to be seen by the naked eye

3. But they are large enough to be scattering a beam of light and makes the path visible.

(b) A colloid is a mixture consisting of dispersed phase and dispersing phase.

(c) Foam is a colloid consisting of dispersed phase gas and dispersing medium solid.

1. Fractional distillation is used to separate a mixture of two or more miscible liquids in which which have a boiling point difference of less than 25K.

2. Fractional distillation is performed using a fractionating column.

3. Petroleum products are purified using fractional distillation and vapours codense at different temperatures.

Fig: Fractional Distillation

Let x g be the mass of potassium sulphate.

We know that

Mass by mass percentage of a solution =

x = 11.1 g

Burning of candle exhibit both physical (melting of wax) and chemical (burning of candle) change.

Mass by mass percentage of a solution=

=

=

(i) Butter from curd.

Centrifugation is the method of choice for separation of butter from curd. In this process the mixture is spun at a specific speed to differentiate the components. The principle is that denser particles are forced to the bottom and lighter particles stay at the top.

(ii) Different pigments from extracts of flower petals

Chromatography can be used for separation of pigments from extracts of plants. It is based on the difference in solubility of the pigments with the solute, which leads to differentiation.