Methods of Separation in Everyday Life — Class 6 Science
Curiosity · Chapter 9
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- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
- Space weighted by chapter size
- Charts from the book's own data
- Traps corrected
Chapter summary
Key ideas & terms
- Handpicking
- Separating small quantities of one component from a mixture by hand, based on differences in size, colour, and shape.
- Threshing and winnowing
- Threshing beats stalks to separate grains; winnowing separates heavier grains from lighter husk using wind or by blowing air.
- Sieving
- Separating the components of a solid mixture by their different particle sizes using a sieve.
- Evaporation
- Separating a dissolved solid from a liquid by letting the liquid turn to vapour, as in obtaining salt from seawater.
- Sedimentation and decantation
- Sedimentation is the settling of a heavier insoluble component at the bottom of a liquid; decantation is gently pouring off the liquid above it.
- Filtration and magnetic separation
- Filtration separates insoluble solids from a liquid using a filter's pores; magnetic separation uses a magnet to pick out magnetic substances.
Extra questions & answers
What is handpicking, and when is it useful?
Handpicking is separating a component from a mixture by hand based on size, colour, and shape; it is useful when the component to be removed is present in small quantities.
What is threshing?
Threshing is the process of beating harvested stalks to separate the grains attached to them.
What is winnowing?
Winnowing is the method of separating heavier grains from lighter husk by dropping the mixture in a flow of wind so that the wind blows the husk away.
When is sieving used?
Sieving is used when the components of a solid mixture have different particle sizes, such as separating bran or stones from fine flour.
How is salt obtained from seawater?
Seawater is kept in shallow pits and exposed to sunlight and air; the water evaporates, leaving behind a solid mixture from which common salt is obtained.
What is the difference between sedimentation and decantation?
Sedimentation is the settling of a heavier insoluble component at the bottom of a liquid, while decantation is the gentle pouring off of the liquid above the settled matter.
What is filtration, and what are the residue and filtrate?
Filtration separates insoluble solids from a liquid using a filter; the solid left on the filter is the residue and the clear liquid that passes through is the filtrate.
What is churning used to separate?
Churning is used to separate lighter butter from buttermilk by spinning curd, with the butter floating to the top.
What is magnetic separation?
Magnetic separation is the separation of magnetic substances, such as iron nails, from non-magnetic substances using a magnet.
How would you separate a mixture of more than two components?
A mixture with more than two components needs a combination of several methods of separation, applied in a suitable sequence based on the properties of the components.
Let us enhance our learning
1. What purpose does handpicking serve in the process of separation? (i) Filtration (ii) Sorting (iii) Evaporation (iv) Decantation
Answer is (ii) Sorting. Handpicking separates useful or unwanted solid particles from a mixture on the basis of differences in size, colour or shape. It sorts the components so that the desired material can be kept and the unwanted material removed, when the amount to be removed is small and can be picked easily by hand.
2. Which of the following substances are commonly separated using the churning method? (i) Oil from water (ii) Sand from water (iii) Cream from milk (iv) Oxygen from air
Answer is (iii) Cream from milk. Churning is used to separate butter or cream which is lighter and fatty from curd or milk. The lighter fat globules collect at the top as butter while buttermilk remains below. It does not apply to oil-water, sand-water or gases in air.
3. Which factor is usually essential for the filtration? (i) Apparatus size (ii) Presence of air (iii) Pore size (iv) Temperature of the mixture
Answer is (iii) Pore size. Filtration works because the filter has tiny pores that allow the liquid or very fine particles to pass through while the larger insoluble solid particles are retained as residue. If pores are too big, impurities will pass; if too small, filtration will be very slow.
4. 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. [ ]
True [T]. Reason: Keeping salt solution in sunlight causes evaporation. Water changes into vapour and escapes, leaving solid salt behind. This is how salt is obtained from sea water in shallow pits.
4. State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s). (ii) Handpicking should be used only when the quantity of one component is less. [ ]
True [T]. Reason: Handpicking is picking particles by hand using differences in size, colour and shape. It is practical only when the unwanted component is present in small amount and can be easily distinguished and picked. For large quantities it is time-consuming and other methods like sieving or winnowing are better.
4. State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s). (iii) A mixture of puffed rice and rice grains can be separated by threshing. [ ]
False [F]. Reason: Threshing is beating stalks to separate grains from stalks. Puffed rice and rice grains are already free grains differing in weight and size. They can be separated by winnowing or handpicking, not by threshing. Corrected statement: A mixture of puffed rice and rice grains can be separated by winnowing / handpicking.
4. State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s). (iv) A mixture of mustard oil and lemon water can be separated by decantation. [ ]
True [T]. Reason: Mustard oil does not dissolve in water and forms a separate lighter layer on top when left undisturbed. After sedimentation, the upper oil layer can be gently poured off by decantation.
4. State with reason(s) whether the following statements are True [T] or False [F]. Also, correct the False statement(s). (v) Sieving is used to separate a mixture of rice flour and water. [ ]
False [F]. Reason: Sieving separates two solids of different particle sizes using a sieve. Rice flour and water is a solid dissolved/suspended in a liquid, which requires filtration or evaporation, not sieving. Corrected statement: A mixture of rice flour and water can be separated by filtration, and a mixture of rice flour and bran or rice grains can be separated by sieving.
5. Match the mixtures in Column I with their method of separation in Column II. (i) Gram flour mixed with black gram
(d) Sieving - The fine flour passes through the holes of the sieve while the larger black gram seeds remain on the sieve because of difference in particle size.
5. Match the mixtures in Column I with their method of separation in Column II. (ii) Chalk powder mixed with water
(e) Filtration - Chalk powder is insoluble in water and can be retained as residue on filter paper while clear water passes through as filtrate.
5. Match the mixtures in Column I with their method of separation in Column II. (iii) Corn mixed with potatoes
(a) Handpicking - Corn grains and potatoes differ clearly in size, shape and colour and are present as distinct solids that can be picked by hand and sorted.
5. Match the mixtures in Column I with their method of separation in Column II. (iv) Iron powder mixed with sawdust
(b) Magnetic separation - Iron is a magnetic substance attracted to a magnet while sawdust is non-magnetic, so a magnet pulls out iron particles.
5. Match the mixtures in Column I with their method of separation in Column II. (v) Oil mixed with water
(c) Decantation - Oil is immiscible and lighter than water, forming a separate layer that can be poured off after settling.
6. In what situations would you use decantation instead of filtration to separate solids from liquids?
Use decantation when the solid is heavy, insoluble and settles quickly to the bottom as sediment, and you need a quick, simple separation without a filter. For example, washing rice or pulses, or removing tea leaves after settling, or separating sand from water coarsely. Filtration is better when particles are very fine, do not settle easily, or when you need very clear liquid, because decantation leaves some fine particles behind.
7. Can you relate the presence of nasal hair to any separation process?
Yes, nasal hair acts like a filter. As we breathe in, air passes through the hairs which trap dust, pollen and other larger solid particles, allowing only clean air to go to the lungs. It is similar to filtration where pores of the filter retain unwanted particles and allow the desired fluid to pass.
8. During the COVID-19 pandemic, all of us wore masks. Generally, what material are they made of? What is the role of these masks?
Most masks are made of layers of non-woven fabric, commonly polypropylene, and sometimes cotton, muslin or filter paper-like material. They work as filters. The tiny pores allow air to pass but block droplets, dust and germs. They filter out virus-carrying droplets from inhaled and exhaled air, protecting the wearer and others, similar to filtration and sieving on a very fine scale.
9. A mixture containing potatoes, salt and sawdust has been given to you. Outline a stepwise procedure for separating each component from this mixture.
Step 1 - Handpicking: Potatoes are large and distinct, so pick them out by hand and keep aside. Step 2 - Add water: Put the remaining salt + sawdust in water and stir. Salt dissolves to form salt solution while sawdust does not dissolve and floats or suspends. Step 3 - Filtration: Filter the mixture through filter paper or muslin cloth. Sawdust remains as residue on the filter, clear salt solution collects as filtrate. Dry the sawdust. Step 4 - Evaporation: Heat the salt solution gently in a china dish or keep it in sunlight. Water evaporates leaving solid salt behind. Test by touching the white residue.
10. 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.
Correct choices: felt thirsty, fetch some water, water was muddy and unfit for drinking, she filtered the muddy water using a piece of muslin cloth, she boiled the water for about 10 minutes, After boiling she filtered it again and made it fit for drinking. Sequence: She first allowed sedimentation by keeping water undisturbed, then decanted and filtered to remove mud, then boiled to kill germs, then cooled and filtered again if needed. Suitable title: Clever Leela Purifies Water or How Leela Made Muddy Water Drinkable. The story shows sedimentation, decantation, filtration and boiling used together to make water safe.