We separate components of a mixture (combination of 2+ substances) for two major reasons:
To Remove
Non-useful or harmful components (e.g. stones from rice)
To Separate
Two different but highly useful components (e.g. butter from milk)
1. Handpicking
Picking out impurities by hand from a mixture.
- Criteria: Impurities must look different in size, shape, or color.
- Condition: Impurities must be in small quantities.
- Example: Separating stones/husk from rice, wheat, or pulses.
2. Threshing
Separating grains from harvested dry stalks.
🌾 Helps extract thousands of tiny grains quickly!
3. Winnowing
Separating lighter components from heavier ones using wind/blowing air.
🌾 Heavier Grains → Fall straight down in a heap.
💨 Lighter Husk → Blown away by the wind, forming a separate pile.
🛠️ Traditional Tool: Bamboo tray called a soop.
4. Sieving
Using a sieve to separate solid particles of different sizes.
- Fine particles pass through the holes; larger impurities remain on top.
- Examples: Removing bran from flour; separating pebbles and stones from sand at construction sites.
Sedimentation
The process where the heavier, insoluble solid settles to the bottom of the container when left undisturbed.
Decantation
Pouring out the upper clean liquid into another vessel without disturbing the settled sediment.
💡 Also used to separate immiscible liquids (e.g., Oil & Water layer).
Churning (Centrifugation)
Vigorously spinning or shaking liquid mixtures like curd or milk using a wooden churner (mathni).
Result: Lighter butter floats to the top, buttermilk stays below!
Separating insoluble solids from a liquid using a medium with tiny pores that allow only the liquid to pass.
Available Filter Mediums:
Strainer
Fine Cloth
Filter Paper
Converting a liquid into gas (vapor) to separate a dissolved solid from a liquid.
How We Obtain Salt
💡 Did you know? The water bodies like Sambhar Lake in Rajasthan are huge natural sources of common salt in India!
Separating magnetic materials (like iron) from non-magnetic mixtures (like sawdust, sand, or municipal waste).
In Modern Recycling:
Gigantic magnets fitted to cranes are lowered over heaps of scrap waste to attract and separate scrap iron from plastic, wood, and concrete.
🫖 Evolution of Tea Bags
First made of silk (which held leaves well but did not fall apart in hot water), then gauze/muslin, and finally modern filter paper.
🌀 Custom Water Filters
Apart from filter paper, materials like cotton, charcoal, and layers of sand & gravel are highly effective natural filters used since ancient times.
Match the process to the property difference: