Methods of Separation in Everyday Life
Choosing a method
Choose the best way to separate different mixtures.
Malli and Valli's 'Bharat ki Yatra' (tour of India) ends. On the way they saw handpicking, threshing, winnowing, sieving, evaporation, sedimentation and decantation, filtration, churning and magnetic separation. How do we choose the right one? Look at how the parts of the mixture are different.
| How the parts differ | Method | Example |
|---|---|---|
| a few big, easy-to-see pieces | handpicking | corn mixed with potatoes |
| different sizes | sieving | gram flour with black gram: flour passes, gram stays |
| one heavier, one lighter | winnowing, or sedimentation | grain and husk; sand in water |
| a solid that does not dissolve in a liquid | filtration | chalk powder in water |
| a solid dissolved in a liquid | evaporation | salt in water |
| one part magnetic | magnetic separation | iron powder in sawdust |
| two liquids in separate layers | decantation | oil and water |
Why separate at all? The book's two-basket game shows two purposes:
- to remove a part that is not useful, like small stones from pulses;
- to separate two parts that are both useful, like butter and buttermilk from churned curd.
A mixture with more than two parts needs several methods, one after another. How would you separate potatoes, salt and sawdust?
- Handpick the big potatoes first.
- Put the salt and sawdust in water: the salt dissolves, the sawdust does not.
- Filter the water to take out the sawdust.
- Evaporate the water from the salt solution, and the salt is left.
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