NCERT Solutions Curiosity Chapter 9 Rubbing and blowing roasted peanuts — Activity 9.1: Let us explore
Book page 165 Updated on2026-09-05
Q1.
Take a handful of roasted peanuts and rub them between your palms. What happens?
Answer
The thin, papery red-brown skin comes off the peanuts. After rubbing you are left with two things lying together in your palm:
Peanut seeds — smooth, pale, fairly heavy.
Loose skins — thin, papery flakes, almost weightless.
Why it happens: roasting dries the skin so it shrinks and loses its grip on the seed. Rubbing gives the sideways push that breaks that last grip. This is exactly what threshing does to wheat on a bigger scale — beating loosens what is only lightly attached.
Check it yourself: Try rubbing a raw peanut the same way. The skin does not come off easily, because it is still moist and sticks to the seed.
Q2.
Is it possible to separate the removed skin and the peanuts?
Answer
Yes — and very easily, because the two components are now simply lying mixed together and are very different from each other.
Way to separate
Property it uses
Works well?
Handpicking
Difference in size, colour and shape
Works, but far too slow — there are hundreds of tiny flakes
Blowing air / winnowing
Difference in weight
Best — one puff clears all the skins at once
Sieving
Difference in size
Poor — a flake of skin can be as wide as a seed
The idea to hold on to: a mixture can usually be separated in more than one way. The best method is the one that uses the property in which the two components differ the most. Here that property is weight, not size.
Q3.
Now, try blowing it. What do you observe?
Answer
The papery skins fly away with the puff of air and float down some distance away. The peanut seeds stay in your palm, hardly moving.
Light skin + moving air → carried far away
Heavy peanut + moving air → stays where it was
Why it happens: the moving air pushes on both. But the skin has very little weight and a fairly large flat surface, so the push of the air easily lifts and carries it. The peanut is many times heavier for its size, so the same push is far too weak to move it.
Tip: Do this over a newspaper spread on the floor, and blow gently and steadily. A sudden hard blow scatters the peanuts too and spoils the separation — which is why a farmer lets the steady wind do the work instead of a sudden gust.
Q4.
Which of these components—removed peanut skins or peanuts are blown away?
Answer
The removed peanut skins are blown away. The peanuts are not.
Why: the skins are the lighter component of the mixture. Blowing air always separates a mixture into a heavier part that falls close by and a lighter part that is carried away. This single observation is the whole principle of winnowing, which farmers use on the threshed wheat in the very next paragraph of the chapter.
Did you know? The same trick is used in your kitchen. After roasting and rubbing chana (gram), people toss it in a plate near an open window — the skins drift off and the gram stays back.