What purpose does handpicking serve in the process of separation?
- Filtration
- Sorting
- Evaporation
- Decantation
Answer
Sorting
Reason — Handpicking is the method of picking out substances by hand from a mixture on the basis of differences in their size, colour and shape. In this way, it sorts the useful component from the unwanted one, for example, picking small stones and husk out of grains.
Filtration separates insoluble solids from a liquid. Evaporation separates a dissolved solid from a liquid. Decantation separates a liquid from settled solids. None of these is the purpose of handpicking.
Which of the following substances are commonly separated using the churning method?
- Oil from water
- Sand from water
- Cream from milk
- Oxygen from air
Answer
Cream from milk
Reason — Churning is used to separate the lighter component that floats at the top. When curd or milk is churned, the lighter cream (butter) collects at the top and is separated.
Oil from water is separated by decantation, sand from water by filtration or sedimentation, and oxygen is not separated from air by churning.
Which factor is usually essential for the filtration?
- Apparatus size
- Presence of air
- Pore size
- Temperature of the mixture
Answer
Pore size
Reason — Filtration works because of the fine pores present in the filter. These pores allow the liquid to pass through while the larger insoluble solid particles are held back. The size of the pores decides which particles can pass and which are retained.
Apparatus size, presence of air and temperature of the mixture do not decide the separation in filtration.
State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s).
(i) Salt can be separated from salt solution by keeping it under the Sun.
(ii) Handpicking should be used only when the quantity of one component is less.
(iii) A mixture of puffed rice and rice grains can be separated by threshing.
(iv) A mixture of mustard oil and lemon water can be separated by decantation.
(v) Sieving is used to separate a mixture of rice flour and water.
Answer
(i) True
(ii) True
(iii) False
Correct Statement — A mixture of puffed rice and rice grains can be separated by winnowing, as the lighter puffed rice is blown away by air while the heavier rice grains are left behind. Threshing is used to separate grains from harvested stalks.
(iv) True
(v) False
Correct Statement — Sieving is used to separate a solid-solid mixture whose particles differ in size. A mixture of rice flour and water is a solid-liquid mixture and is separated by filtration.
Match the mixtures in Column I with their method of separation in Column II.
| Column I | Column II |
|---|---|
| (i) Gram flour mixed with black gram | (a) Handpicking |
| (ii) Chalk powder mixed with water | (b) Magnetic separation |
| (iii) Corn mixed with potatoes | (c) Decantation |
| (iv) Iron powder mixed with sawdust | (d) Sieving |
| (v) Oil mixed with water | (e) Filtration |
Answer
| Column I | Column II |
|---|---|
| (i) Gram flour mixed with black gram | (d) Sieving |
| (ii) Chalk powder mixed with water | (e) Filtration |
| (iii) Corn mixed with potatoes | (a) Handpicking |
| (iv) Iron powder mixed with sawdust | (b) Magnetic separation |
| (v) Oil mixed with water | (c) Decantation |
In what situations would you use decantation instead of filtration to separate solids from liquids?
Answer
Decantation is used when the solid is insoluble and heavy enough to settle down at the bottom of the liquid, leaving a clear liquid above. In such cases the settled solid is left undisturbed and the clear liquid is simply poured off, without the need for a filter. For example, separating settled tea leaves from tea or washing and cleaning rice and pulses. Filtration is preferred when the solid particles are very fine and do not settle down easily.
Can you relate the presence of nasal hair to any separation process?
Answer
Yes, the presence of nasal hair can be related to filtration. The fine hairs inside the nose act like a filter by trapping some dust and dirt particles present in the air we breathe. This helps prevent larger particles from entering deeper into the respiratory system, just as a filter retains solid particles while allowing air or liquid to pass through.
During the COVID-19 pandemic, all of us wore masks. Generally, what material are they made of? What is the role of these masks?
Answer
Masks are generally made of layers of cloth or non-woven fabric. They work on the principle of filtration. The mask material allows air to pass through while trapping many respiratory droplets and some airborne particles. Thus, masks help reduce the spread and inhalation of potentially harmful particles, providing protection against respiratory infections.
A mixture containing potatoes, salt and sawdust has been given to you. Outline a stepwise procedure for separating each component from this mixture.
Answer
The components can be separated step by step as follows:
- The potatoes are large in size, so they are separated first from the mixture by handpicking.
- To the remaining mixture of salt and sawdust, add water and stir. The salt dissolves in water forming a salt solution, while the sawdust is insoluble and floats on the surface.
- Filter this mixture. The sawdust is left behind on the filter paper as residue, and the salt solution passes through as filtrate.
- Heat the salt solution and let the water evaporate. The water escapes as vapour and the salt is left behind as a solid.
In this way, the three components, potatoes, sawdust and salt, are separated using handpicking, filtration and evaporation.
Read the following story titled 'Intelligent Leela' and tick the most appropriate options. Provide a suitable title of your choice for the paragraph.
Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty/hungry, she went to the nearby pond to fetch some water/grains. After obtaining some water in the container, she noticed that the water was muddy and fit/unfit for drinking. To purify the water, she kept it for some time and then she filtered/churned the muddy water using a piece of paper/muslin cloth. Leela, then, cooled/boiled the water for about 10 minutes in a covered pan. After cooling/boiling, she filtered/churned it again and made it fit/unfit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.
Answer
The completed paragraph with the correct options is given below:
Leela was working in the farm with her father when she realised that they left their drinking water at home. Before her father felt thirsty, she went to the nearby pond to fetch some water. After obtaining some water in the container, she noticed that the water was muddy and unfit for drinking. To purify the water, she kept it for some time and then she filtered the muddy water using a piece of muslin cloth. Leela, then, boiled the water for about 10 minutes in a covered pan. After cooling, she filtered it again and made it fit for drinking. She served this water to her father while having food, who blessed her and appreciated her efforts.
Suitable title: Purification of Drinking Water