In our daily life we come across so many substances that need to be separated from other substances in a mixture. For example: separation of stones, small insects and husk from grains before cooking. There are various techniques that are used for the separation of substances from other substances. Separation technique is a method in which mass transfer takes place and converts a mixture of substances into two or more substances. For example: handpicking, winnowing, threshing, sedimentation, filtration etc. Two or more substances which are separated using various methods of separation can be useful or useless. Sometimes both the substances being separated are important. On the other hand sometimes only one of the substance is useful and the other is useless. Segregation of substance is also used to remove harmful substances from a useful substance.
Need for Separation of Substances:
- To get two or more useful products.
- To remove impurities from the useful product or remove the harmful substances from the useful substances.
Segregation of substances is carried out in two ways:
- Dry conditions: Some mixtures are separated in a dry state. No liquid is added while separating substances. Some of the separation techniques carried in dry conditions are handpicking, threshing, winnowing, sieving. Handpicking is a method in which impurities are removed just by picking the impure substances by hands. Threshing is a method used to remove stalks from the grains. Winnowing is a method in which heavier components of the mixture are separated from the lighter components with the help of wind.
- Wet conditions: Substances can be separated into a liquid or aqueous state. Separation techniques used under this condition are sedimentation, decantation etc.
Substances can be separated according to their size, solubility, weight, density or materials etc. These materials can be solids, liquids, or gases.
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