separation of substances ncert chapter vi, cbse, india

Separation of Substances

Holiday Homework

Vi A

Roll No:35

Spandan Bhattacharya

Contents • Sedimentation and decantation• Winnowing and threshing • Filtration• Sieving

Advanced methods of separation• Fractional distillation• Crystallization• Sublimation

Sedimentation and Decantation

• Sedimentation – Heavy impurities in water settle down after some time.

• Decantation – The clear liquid above the impurities is poured in another container.

Winnowing and Threshing

• Threshing – Mainly used to separate grains from other parts by beating free the grains.

• Winnowing – Used to separate grains from impurities like husk by dropping it from an height. All light impurities are separated due to a fan or wind.

Threshing

Winnowing

Sieving

• Used to separate impurities of different volume.

• All impurities of smaller size fall down through holes in the container.

Filtration

• Filtration – Used for separating different substances, usually solids mixed with liquids, with filter paper, funnel and container.

• The substance collected is filtrate which is free of all insoluble impure substances.

A method in which a substance when kept in different temperatures ,different materials are formed, e.g.: Crude oil when heated at different temperatures forms petrol, naphthalene kerosene, diesel etc.

Fractional Distillation

Sublimation

A mixture of solid substances, such as camphor, benzoic acid, ammonium chloride, iodine etc.

Containing non-volatile substances, when heated, change directly into vapour without passing through the liquid state.

Crystallization• Substances that get converted to

vapors without passing through the liquid state on heating, e.g. naphthalene, benzoic acid and camphor, undergo sublimation.

• The vapor on cooling, gives crystals of the pure solid compound. The crystalline material so obtained is called sublimate.

• The sublimation process can be described by the equation.

• The technique of sublimation is employed for separating (or purifying) volatile solid substances, which sublime on heating from the non-volatile substances.