For a common man, pure substance that it is not adulterated. for example, for a common man, pure milk means the liquid material that is given by cow or buffallo and it is not mixed with water or other materials to thicken it. But for a chemist, any milk is not a pure substance. Milk is a mixture of water, fats and proteins. These materials are different in milk obtained from different source. Similarly, pure fruit juice for a common man means that it is not mixed with fruit juice of other fruits water or salt. But for a chemist, any fruit juice is a mixture of water and several other substances. For a common man pure gold means gold of a given composition. But a chemist known that no ornaments can be made from pure gold. All ornaments of gold contain gold and copper.

(i) Potassium chloride crystallises out.
(ii) Sugar remains as residue in the form of a solid mass.
(iii) A black coloured compound is formed.

Step 1: Pass the mixture through a filter paper, water and oil will pass through, iron and sulphur will be left as a residue.
Step 2: The liquid separated is a mixture of water and oil. Take it in a separating funnel. Oil is generally lighter and makes the upper layer. The water, the lower layer can be poured out. Oil will remain in the funnel.
Step 3: Dry the solid residue. Pass a magnet over the mixture. Iron filings get stuck to the magnet whereas sulphur remains unaffected. Thus iron and sulphur get separated. Water and oil are compounds. Iron and sulphur are elements.

(i) Chromatography: Separation of components of the ink. Different components travel at different speeds in a common solvent.
(ii) Distillation: Separation of soluble solids from their solutions. The mixture is heated and only the solvent boils and is collected through the condenser e.g., the mixture of ink and water.
(iii) Evaporation: Separation of salt from its water solution. When a solution is heated, water evaporates leaving the salt behind.
(iv) Fractional distillation: Separation of ethanol and water mixture. Different liquids boil off at different temperatures. When heated they boil off and condense at different times.
(v) Filtration: Separation of sand and water. The solid remains on the filter paper and the liquid goes through the paper into the beaker.

Water is considered an element because:
(i) Water is composed of two elements: hydrogen and oxygen.
(ii) The ratio of hydrogen and oxygen from its constituent elements: hydrogen and oxygen.
(iii) The properties of water are different from its constituent element: hydrogen same.
(iv) Water can be decomposed by chemical means only (e.g. electrolytically) into hydrogen and oxygen.

(a) (i) centrifugation        
(ii) filtration
(iii) Separating funnel      
(iv) Evaporation
(v) Sublimation              
(vi) Winnowing
(b) (i) Physical change    
(ii) Chemical change
(iii) Chemical change      
(iv) Physical change.

Physical change. it is a temporary change in which the composition and chemical nature of the substance remains the same but the state of the substance and physical change. For example, when ice changes into water and water changes into vapours. The different states have differnt appearance and display different physical properties but they are chemically same.
Chemical change. A chemical change is a permanent change in which not only physical properties but chemical properties also change. This is because new substance/s is formed in a chemical change. Burning of candle is a chemical change. here both the physical and chemical change are taking place and new substance are formed.

Advantages of crystallisation:
(i) Fine crystals of the substance are obtained
(ii) Solids which decompose on heating can be safely purified.
Disadvantages of crystallisation:
(i) Some substance remains with the liquid/ solvent.
(ii) liquid needs to be purified for further use.

Chromatography is the technique whereby different soluble components of a mixture are separated due to their differential movement over a stationary phase under the influences of the mobile phase, i.e., solvent. If water is the solvent then the component that is more soluble in water will move faster. In this way, different components get separated
The technique of chromatography is used to separate
(a) Components of dyes
(b) Pigments from natural colours.
(c) Amino acids.

Chromatography is the technique whereby different soluble components of a mixture are separated due to their differential movement over a stationary phase under the influences of the mobile phase, i.e., solvent. If water is the solvent then the component that is more soluble in water will move faster. In this way, different components get separated
The technique of chromatography is used to separate
(a) components of dyes
(b) pigments from natural colours.
(c) amino acids
(d) sugars from a urine sample
(e) drugs in blood.

A colloidal solution is said to be intermediate state of the solution and the suspension. it neither a true solution is said to be intermediate state of the solution and the size is between 1 nm to 100 nm. For example, a solution, the particle size is between 1 nm to 100 nm. For example, a solution of soap in water, milk, blood, writing links are some of the colloidal solutions. Through these particles are 10 to 1000 times the size of a single small molecule, these are not visible to naked eyes. But these are larger enough to scatter the light that passes through the dispersion medium.The medium of colloidal solution is Known as dispersed phase (dispersion medium) an the particles dissolved are called dispersed phase. In milk, water is dispersion phase and fats, proteins etc. are dispersed  phase. In fog, water droplets from the dispersed phase and air is dispersing medium.

A colloidal solution is said to be intermediate state of the solution and the suspension. it neither a true solution is said to be intermediate state of the solution and the size is between 1 nm to 100 nm. For example, a solution, the particle size is between 1 nm to 100 nm. For example, a solution of soap in water, milk, blood, writing links are some of the colloidal solutions. Through these particles are 10 to 1000 times the size of a single small molecule, these are not visible to naked eyes. But these are larger enough to scatter the light that passes through the dispersion medium.The medium of colloidal solution is Known as dispersed phase (dispersion medium) an the particles dissolved are called dispersed phase. In milk, water is dispersion phase and fats, proteins etc. are dispersed phase. In fog, water droplets from the dispersed phase and air is dispersing medium.

(i) True Solution. A true solution is defined as a homogeneous mixture of two or more substances. The term homogeneous means that every portion of the solution has the same properties, e.g., sugar dissolved in water, iodine in ethyl alcohol (tincture).
(ii) Solute. The substance(s) present in smaller proportions in a solution is called the solute.
(iii) Solvent. The substance present in a larger in large proportion in a solution is called the solvent. If a homogeneous mixture or a solution is formed by dissolving 2 g salt in 100 g water, then salt is the solute and water is the solvent.
(iv) Solubility. The maximum amount of the solid that can be dissolved in a given amount of the solvent (water) is termed its solubility at that temperature.

Homogeneous mixture Heterogeneous mixture (i) it has no visible boundary or boundaries of separation between its constituents. (i) It has visible boundary/boundaries of separation between its constituents. (ii) It has a uniform composition throughout its mass. (ii) The composition of the mixture varies from mass to mass (iii) It does not show the Tyndall effect (iii) It shows the Tyndall effect.