After preparing tea, how do you remove the tea leaves?
Answer
There are two ways, and the chapter shows both.
With a strainer — filtration. Pour the tea through a tea strainer. All the leaves are held back in the mesh and clear tea runs into the cup.
Without a strainer — sedimentation followed by decantation. Leave the pan undisturbed for a while so the leaves settle at the bottom, then tilt the pan gently and pour the tea into the cup, stopping before the sediment reaches the lip.
Sedimentation and decantation are two steps of the same job: first let the heavy leaves settle, then pour the clear tea away from them.
Which is better: filtration, because it removes every leaf. Decantation is quicker and needs no equipment, but a few fine leaves always come along with the liquid — which is why Dada still gets some leaves in his mouth.
Tip: Decantation works only if the solid is heavier than the liquid and insoluble in it, so that it settles. Sugar dissolved in the tea can never be decanted off.
Q2.
In the chapter ‘Materials Around Us’, you have studied that oil does not mix with water and forms a separate layer when left undisturbed for some time. Which method of separation would you use to separate oil and water?
Answer
Decantation.
Leave the mixture undisturbed until two clear layers form — oil on top, water below.
Tilt the vessel slowly and pour off the upper oil layer into another container; or use a small tap at the bottom (a separating funnel) to run the lower water layer out first.
Why it works: oil and water are immiscible — they do not mix into each other. And oil is lighter (less dense) than water, so it always floats. Because the boundary between the two layers is sharp, the top layer can simply be poured away from the bottom one.
Why not filtration? A filter separates a solid from a liquid. Oil is a liquid — it would simply run through the filter paper along with the water. In the same way, milk cream is skimmed off the top of milk because it is lighter.
Q3.
Balan asks Malli if he could use a tea strainer to filter muddy water. Let us try and find out.
Answer
Not properly. A tea strainer takes out only the biggest bits — leaves, twigs, grit. The water that comes through is still brown and muddy.
Filter used
Pore size
Result with muddy water
Tea strainer
Fairly large holes
Big pieces removed; water still muddy
Muslin cloth (a few layers)
Small pores between the woven threads
Much clearer, but a fine haze remains
Filter paper
Very fine pores
Mud held back as residue; clear filtrate collected
Why: a filter stops only those particles that are bigger than its pores. Mud particles are extremely fine, so they slip straight through the wide holes of a tea strainer. To stop them, the pores must be finer than the particles.
Important: even filter paper does not make pond water safe to drink. It removes what you can see, but not the germs. Water must also be boiled (or treated) afterwards — which is just what Leela does in Question 10 of the exercise.
Q4.
Why should we use a piece of cloth?
Answer
Because a woven cloth is already a ready-made filter. In a piece of cloth there are very small holes or pores between the woven threads, and these pores do the filtering.
The pores are much finer than the holes of a tea strainer, so far more mud is held back.
Cloth is cheap, available in every home and can be washed and used again.
Folding it gives several layers, which makes the path narrower still and traps more.
An old Indian practice: people have strained drinking water through cloth for centuries — the chapter says so plainly. A folded cotton or muslin cloth over the mouth of a matka still filters water in many villages.
Did you know? The same idea explains a malmal tea bag, a chhanni used for curd, and even the cloth mask you wore during COVID-19 — all of them work because of the pores between the threads.
Q5.
How many layers of cloth do I need to use to get clear water?
Answer
There is no single fixed number — it depends on how muddy the water is and how fine the cloth is. As a working rule, three to four layers of clean cotton or muslin cloth give clearly better water than one.
1 layer → some mud passes through, water still brownish
2–3 layers → noticeably clearer 4 layers → clearer still, but the water now trickles very slowly
Why more layers help: each layer has its own pores, and the pores of one layer do not line up with those of the next. So a particle that slips through the first layer is likely to be stopped by the second or the third. Effectively, more layers means finer filtering.
The trade-off: beyond a point extra layers only slow the flow to a drip without making the water much cleaner. If the water is still not clear, do not keep adding cloth — let the mud settle first (sedimentation) and then filter, or use a finer filter such as filter paper.