Sieving
Class 6 Science · Chapter 9: Methods of Separation in Everyday Life · NCERT Curiosity section Ch 9
Learn
Before making rotis, Ira's father passes the flour through a sieve (chhalni). The fine flour goes through the tiny holes; the bran and small lumps stay on top. This is sieving: separating particles of different sizes.
At building sites, workers throw sand against a large slanting wire sieve to separate it from pebbles and stones. Sieves with bigger or smaller holes are chosen depending on what you want to keep.
A tea strainer is a small sieve too: the liquid tea passes through, the tea leaves stay behind.
Explore: which method?
- Sort each mixture by the best method.
Remember
- Sieving separates particles of different sizes using a sieve.
- Choose the hole size depending on what you want to keep.
Quick check
Sieving separates particles that differ in …
- size
- colour
- smell
- taste
Answer
size. Smaller particles pass through the holes; bigger ones stay behind.
Think about it
Could you separate salt from sugar by sieving? Why or why not?
One answer
Usually not: salt and sugar grains are about the same size, so both pass through the same sieve. Sieving only works when the particles are of clearly different sizes.
Practice
Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.