**Key Definitions:**
**Handpicking:** Removing unwanted particles by hand from a mixture using differences in size, colour, and shape. Used when unwanted items are few and easy to spot.
**Threshing:** Beating dried stalks to separate grains from them. Farmers do this in fields after harvest.
**Winnowing:** Separating light husk from heavy grains using wind or blowing air. Done with a bamboo tray called soop.
**Sieving:** Pouring mixture through holes in a sieve. Small particles pass through, large particles stay on top. Used when particle sizes are different.
**Evaporation:** Heating a liquid mixture so water disappears into air, leaving solid particles (like salt) behind. Happens in sun or with heat.
**When to Use Which Method:**
Handpicking → Few unwanted particles, easy to see
Threshing → Separating grains from stalks
Winnowing → Separating light from heavy parts
Sieving → Separating by particle size
Evaporation → Separating dissolved solids from liquids
**Diagrams to Remember:** Soop (bamboo tray) used in winnowing, sieve showing holes, salt crystals on paper after evaporation.
**Don't Confuse:** Threshing (beating) is NOT handpicking (removing by hand). Winnowing (using air) is NOT sieving (using holes). Evaporation leaves salt behind; it does NOT remove salt.
Q1. Which method is used to remove small stones from rice before cooking?
Answer: A — Handpicking is used when unwanted items like small stones are few and can be easily removed by hand based on their appearance.
Q2. What is the process called when farmers beat dried wheat stalks to separate grains?
Answer: B — Threshing is the specific process of beating stalks on a wooden log to separate grains from the dried plant material.
Q3. Fill in the blank: __________ is the method of separating lighter and heavier components using wind or blowing air.
Answer: C — Winnowing specifically uses wind or air movement to blow away light husk while heavy grains fall down separately.
Q4. A cook needs to remove bran from flour before making soft bread. Which separation method should be used?
Answer: C — Sieving is used because bran particles are larger than flour particles, so they stay on the sieve while fine flour passes through.
Q5. Which of these is an example of winnowing?
Answer: B — Winnowing uses a bamboo tray and wind to separate light husk from heavy grains, which is exactly what the farmer is doing.
Q6. Looking at the diagram of a sieve, why do small flour particles pass through while bran stays on top?
Answer: B — Sieving works by having holes of a specific size; particles smaller than the holes pass through, and larger particles stay on top.
Q7. What happens to seawater when it is left in shallow pits under the sun?
Answer: A — Evaporation causes water to disappear due to heat from the sun, leaving behind solid salt crystals that can be harvested.
Q8. Valli is separating peanut skins from peanuts by blowing air at them. Which separation method is she using?
Answer: C — This is winnowing because she is using air to separate lighter components (skins) from heavier components (peanuts).
Q9. Why is winnowing faster than handpicking for separating grains from large piles of husk?
Answer: B — Winnowing is faster because the natural force of wind or blown air separates the mixture automatically, while handpicking requires removing each item one by one.
Q10. If you see white patches on dark-coloured clothes during hot summers, how are these patches formed?
Answer: A — When sweat (which contains salt) evaporates in the heat, the solid salt is left behind as white patches on the dark fabric.
What is handpicking?
It is picking unwanted particles from a mixture by hand, based on differences in size, colour, and shape.
When is handpicking used?
Handpicking is used when unwanted items are present in small quantities and can be easily removed by hand.
What is threshing?
Threshing is the process of beating dried wheat stalks to separate grains from the stalks.
What is winnowing?
Winnowing is separating heavier grains from lighter husk by using wind or blowing air.
What tool is used for winnowing?
A soop (bamboo tray) is traditionally used to toss the mixture so wind blows away the light husk.
What is sieving?
Sieving is passing a mixture through a sieve so small particles pass through holes while larger particles stay on top.
When do we use sieving?
Sieving is used when components of a solid-solid mixture have different sizes, like removing bran from flour.
What is evaporation?
Evaporation is the process where water in a solution disappears due to heat, leaving solid particles like salt behind.
How is salt obtained from seawater?
Seawater is kept in shallow pits in sunlight, water evaporates, and salt crystals are left behind.
Why is winnowing better than handpicking for large amounts of grain?
Winnowing is faster and easier because wind automatically separates the light husk from heavy grains without manual effort.
What is handpicking? Give one example from your kitchen. [1 mark]
Define handpicking as removing unwanted particles by hand based on differences in appearance. Example: removing stones from rice or black peppers from pulao.
Explain the difference between threshing and winnowing with one example each. [2 marks]
Threshing: beating stalks to separate grains (done first in fields). Winnowing: using wind to separate light husk from heavy grains (done after threshing using a bamboo tray).
Why is winnowing better than handpicking for separating large quantities of grain from husk? Explain with a reason from daily farm life. [3 marks]
Handpicking would take very long time and many people working manually. Winnowing is faster because wind automatically blows away light husk while heavy grains fall down; farmers can process large quantities in fields without exhausting manual effort.
Draw a labelled diagram of winnowing using a bamboo tray (soop) and explain how it separates grains from husk. What role does wind play? [5 marks]
Diagram should show: farmer holding soop/bamboo tray, direction of wind/air, light husk being blown away, and heavy grains falling down. Explanation: wind carries away light husk particles while heavier grain falls straight down due to gravity, separating the two components based on weight difference.
True or False: (a) Sieving separates mixture based on particle size. (b) Evaporation makes salt disappear from seawater. Give reasons for each. [2 marks]
(a) True—sieving uses holes of specific size to let small particles pass and large particles stay on top. (b) False—evaporation removes water and leaves salt crystals behind; salt becomes visible as white crystals, not disappears.
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