A pure substance consists of single type of particles that is all the constituent particles of a pure substance have same chemical nature. 

The difference between between homogeneous and heterogeneous mixtures:

Homogenous Mixture:

(i) A homogeneous mixture is a mixture having a uniform composition throughout the mixture.

(ii) For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures.

Hetrogenous Mixture: 

(i) On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture.

(ii) For example, composition of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.

Mass of solute (sodium chloride) = 36 g (Given)

Mass of solvent (water) = 100 g (Given)

Then, mass of solution = Mass of solute + Mass of solvent

= (36 + 100) g

= 136 g

Kerosene and petrol are miscible liquids also the difference between their boiling point is more than 25 ºC so they can be separated by the method of distillation.

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

By Centrifugation.

By Evaporation.

 By Sublimation.

The crystallisation method is used to purify solids. In this methods solids obtained in purified crystal form.

Evaporation.

The separation of Ammonium chloride from a mixture containing sodium chloride and ammonium chloride is separated easily by Sublimation method.

We will apply Chromatography for the separation of Different pigments from an extract of flower petals.

The separation techniques which we will apply for the separation of Oil from water Using separating funnel.

The separation techniques  which we will apply for the separation of Iron pins from sand is Magnetic separation.

We apply for the separation of wheat grains from husk is Winnowing method.

Centrifugation.

First, water is taken as a solvent in a saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the strainer asresidue. Sugar is added tothe filtrate, which dissolves in the filtrate. The resulting solution is the required tea.

(a) Since 62 g of potassium nitrate is dissolved in 100g of water to prepare a saturated solution at 313 K, 31 g of potassium nitrate should be dissolved in 50 g of water to prepare a saturated solution at 313 K.

(b) The amount of potassium chloride that should be dissolved in water to make a saturated solution increases with temperature. Thus, as the solution cools some of the potassium chloride will precipitate out of the solution.

(c) The solubility of the salts at 293 K are:

Potassium nitrate – 32 g
Sodium chloride – 36 g
Potassium chloride – 35 g
Ammonium chloride – 37 g

Ammonium chloride has the highest solubility at 293 K.

(d) The solubility of a salt increases with temperature.

Take a sample of colourless liquid and put on stove if it starts boiling exactly at 100 ºC then it is pure water. Any other colourless liquid such as vinegar always have different boiling point. Also observe carefully that after some time whole liquid will convert into vapour without leaving any residue.

A solution is a homogeneous mixture of two or more substances. Ex. – lemonade and soda water etc.

A mixture is a combination of two or more substances which show the properties of each of the substance combined. A mixture of iron powder and sulphur show the properties of both sulphur and iron.

Homogenous mixture – Mixture having uniform composition are called homogeneous mixture.

Heterogeneous mixture– those mixture that do not have uniform composition are called heterogeneous mixture

1. Colloidal solution

2. Concentration solution

3. Suspension

suspension is a heterogeneous mixture which solids are dispersed in liquids are called suspension.

The component of the solution that is dissolved in the solvent (usually present in lesser quantity) is called the solute.

Properties of a solution:

(i) A solution is a homogeneous mixture.

(ii) The particles of a solution are smaller than 1 nm.

(iii) They cannot be seen by naked eyes.

(iv) They do not scatter a beam of light passing through the solution.

(v) The path of light is not visible in a solution.

The properties of suspension:

(i) Suspension is a heterogeneous mixture.

(ii) The particles of a suspension can be seen by the naked eye.

(iii) The particles of a suspension scatter a beam of light passing through it and make its path visible.

(iv) They can be separated from the mixture by the process of filtration.

The properties of a colloid:

(i) A colloid is a heterogeneous mixture.

(ii) The size of particles of a colloid is too small to be individually seen by naked eyes.

(iii) Colloids are big enough to scatter a beam of light passing through it and make its path visible.

(iv) They do not settle down when left undisturbed, that is, a colloid is quite stable.

The amount of the solute present in the saturated solution at this temperature is called its solubility.

The process of separating a solid from a liquid by pouring out the liquid is known as decantation.

The process of separating a solid from a liquid by pouring out the liquid is known as decantation.

By the centrifugation.

This process of separation of components of a mixture is known as chromatography.

Chemical change brings change in the chemical properties of matter and we get new substances. A chemical change is also called a chemical reaction.

By distillation.

Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.

An element is a pure substances of matter. Which can’t be broken down into simpler substances by chemical method.

Ex. -  Copper, Iron, Alumunium, Oxygen, Nitrogen etc.

1. Metal: Metals are solid and lusterious elements which conduct the electricity and heat. 

2. Non Metal: The elements which are neither solid nor lusterious and don't conduct the heat and electricity.

3. Metalloids: some elements have intermediate properties between those of metals and non-metals they are called metalloids examples: are boron, silicon germanium etc.

Properties of Metals:

• They have a lustre (shine).

• They have silvery-grey or golden-yellow colour.

• They conduct heat and electricity.

• They are ductile (can be drawn into wires).

• They are malleable (can be hammered into thin sheets).

• They are sonorous (make a ringingsound when hit).

Properties of Non-Metals:

 Non-metals usually show some or all of the following properties:

• They display a variety of colours.

• They are poor conductors of heat and electricity.

• They are not lustrous, sonorous and malleable.

A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

​Various methods of seperation are as follow;

1. Evaporation
2. Chromatography.
3. Centrifugation.
4. Sublimation.
5. Filtration.
6. Crystallisation.
7. Distillation.
8. Magnetic separation.
9. Separating Funnel.
10. Winnowing
11. Decantation.
12. Sedimentation.   ​