Chapter 9
🫙 Methods of Separation in Everyday Life
Curiosity | NCERT Grade 6 Science
📚 Table of Contents
📷 Separation methods — winnowing grains from husk using wind
Why separate? In everyday life, we often get mixtures — stones in grain, mud in water, salt in water. We need to separate components to get the pure substance we want. Different methods work for different types of mixtures!
✋ 9.1 Handpicking
📖 Definition
Handpicking = Picking out components by hand from a mixture based on differences in size, colour, or shape of the particles. - Best when unwanted particles are few in number and easy to spot
- Example: Picking pebbles from rice, removing black pepper from pulao
- Cannot use for very fine mixtures or large quantities
🌾 9.2 Threshing
📖 Definition
Threshing = The process of separating grains from stalks by beating the harvested stalks on a hard surface. - Farmers beat wheat/paddy stalks on a wooden log to separate grains
- Modern thresher machines do this quickly for large quantities
- After threshing, grains are mixed with husk → need further separation
📷 Threshing — separating grains from stalks by beating
💨 9.3 Winnowing
📖 Definition
Winnowing = Separating heavier and lighter components of a mixture by wind or by blowing air. - Used to separate grain from husk after threshing
- Farmer stands on raised platform and pours mixture in the direction of wind
- Light husk is blown away; heavy grains fall straight down
- Traditional tool: soop (bamboo tray) — poured in direction of air/wind
📷 Winnowing using a soop (bamboo tray) — husk blown away by wind, grains fall down
🔲 9.4 Sieving
📖 Definition
Sieving = Separating components of a mixture based on difference in particle size using a mesh/sieve. - Fine particles pass through the holes; coarse particles stay on sieve
- Flour sieved to remove bran and small stones before cooking
- Construction sites: sieve to separate sand from pebbles
- Works only when particles have different sizes
☀️ 9.5 Evaporation (Separation)
📖 Definition
Evaporation is used to separate a dissolved solid from a liquid by heating — the liquid evaporates leaving the solid behind. - Used to get common salt from seawater — seawater kept in shallow pits, water evaporates, salt remains
- Can also evaporate using heat (china dish over flame)
- Used in Ayurveda — drying medicinal herbs in shade (slow evaporation)
📷 Getting salt from seawater — evaporation method
🪣 9.6 Sedimentation & Decantation
🔑 Two Related Processes
- Sedimentation = Process by which heavier, insoluble particles settle down at the bottom of a liquid when left undisturbed
- Decantation = Carefully tilting and pouring the liquid above the sediment into another container
- Making tea without a strainer — tea leaves sink, pour tea gently
- Washing rice and pulses — drain water leaving solids behind
- Sand settles in muddy water — decant clear water above
- Decantation doesn't completely separate — some particles still remain
🔽 9.7 Filtration
📖 Definition
Filtration = Process of separating insoluble solid particles from a liquid using a porous material (filter) with small holes. - Tea strainer — separates tea leaves from liquid tea
- Filter paper — tiny pores, very fine separation
- Cloth — woven threads create small pores for filtering
- Works only for insoluble solids — cannot filter dissolved salt from water!
- Gives better separation than decantation
📊 9.8 When to Use Which Method?
| Situation | Method to Use |
|---|---|
| Few stones in rice/grain | Handpicking ✋ |
| Grains from stalks | Threshing 🌾 |
| Grain from husk | Winnowing 💨 |
| Flour from bran | Sieving 🔲 |
| Salt from saltwater | Evaporation ☀️ |
| Sand from water (coarse) | Sedimentation + Decantation 🪣 |
| Mud from water (fine) | Filtration 🔽 |
| Magnetic material from non-magnetic | Magnetic separation 🧲 |
📝 Chapter Summary
- Mixtures need to be separated to get pure components
- Handpicking: by hand, few particles, visible size/colour difference
- Threshing: grains from stalks by beating
- Winnowing: heavy/light by wind — grains fall, husk blown away
- Sieving: different sized particles — fine ones pass through
- Evaporation: dissolved solid from liquid — liquid evaporates, solid remains
- Sedimentation: heavy particles settle; Decantation: pour liquid above sediment
- Filtration: insoluble solid from liquid using a filter; better than decantation
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