CBSE Important Questions Class 6 Science Chapter 9 – Methods of Separation in Everyday Life
Class 6 Science Chapter 9 Methods of Separation in Everyday Life is part of the new NCERT textbook Curiosity. It teaches students that most things around us are mixtures, and that we often need to separate the useful part from the unwanted part. Students learn the common methods of separation: handpicking, threshing, winnowing, sieving, sedimentation and decantation, filtration and evaporation. They also learn the difference between homogeneous and heterogeneous mixtures, and what a saturated solution means.
These CBSE important questions for Class 6 Science Chapter 9 cover identifying mixtures, how a farmer separates wheat from chaff and stones, homogeneous and heterogeneous mixtures, what makes a solid dissolve faster, saturated solutions, separating oil from water, why separation matters in recycling, and common mistakes about mixtures. Every question has a clear step-by-step answer in simple English with figures, so students can practise on their own, parents can check the working, and teachers can use them for class tests. A free printable PDF of these important questions is also available on this page.
Q1. Which of the following is an example of a mixture?
(a) Water
(b) Carbon dioxide
(c) Air
(d) Iron
Answer: (c) Air
A mixture is made of two or more substances mixed together. Air is a mixture of many gases such as nitrogen, oxygen, carbon dioxide and water vapour. Water, carbon dioxide and iron are each made of only one kind of substance, so they are not mixtures.
Q2. Malli and Valli are fascinated by the variety of grains piled up in the courtyard. Their Mami and Mama, along with other community members, are busy separating small stones and husks from the grains with their hands. Malli and Valli are curious to know why this is being done. Their Nani notices their curiosity and explains, "We are removing these stones so that the grains are fit for cooking." They go around the house to see the fields and the cattle. To keep them busy, Nani gives them the challenge of handpicking small stones from grains while keeping their eyes closed.
Answer the following questions based on the paragraph given above:
a. Who explains to Malli and Valli why the stones are being removed from the grains?
b. Why are the community members separating small stones and husks from the grains?
c. How does Nani explain the importance of removing stones from the grains?
Answer: a. Their Nani explains it to them.
b. They are removing the small stones and husks so that the grains become clean and safe to eat. Stones can hurt the teeth and husks are not fit for eating, so they must be taken out before cooking.
c. Nani explains that the grains must be free of stones to be fit for cooking. This method of picking out unwanted bigger pieces by hand is called handpicking, and it is used when the amount of impurity is small.
Q3. A farmer needs to separate a mixture of wheat grains, chaff and small stones. The farmer wants to use traditional methods to achieve this.
a. Describe the sequence of methods the farmer should use to separate the wheat grains, chaff and small stones. Explain the principle behind each method.
b. Why is it important for the farmer to separate the chaff and stones from the wheat grains before storage?
c. If the farmer finds that some chaff is still mixed with the wheat grains after winnowing, what additional method can be used to ensure complete separation?
Answer: a. The farmer should use three methods, one after the other:
1. Threshing: The harvested crop is beaten so that the grains come loose from the stalks and chaff.
2. Winnowing: The mixture is dropped from a height in the wind. The lighter chaff is blown away and the heavier grains fall straight down. The principle is the difference in weight.
3. Handpicking: Any small stones left with the grains are picked out by hand, because they are few and can be seen easily.
b. Chaff left with the grains attracts insects and pests, which spoil the stored grain. Stones can damage the machines when the grain is ground into flour. Clean grain also sells at a better price.
c. The farmer can use sieving. A sieve with the right size of holes lets the small chaff pieces fall through while the bigger wheat grains stay behind.
Q4. Answer the following questions based on the image given below:
a. Identify which beaker contains a homogeneous mixture and which contains a heterogeneous mixture.
b. Describe the characteristics of both the mixtures.
Answer: a. The beaker with sugar dissolved in water is a homogeneous mixture. The beaker with sand and water is a heterogeneous mixture.
b. Sand and water (heterogeneous): The sand does not dissolve. We can see the sand particles separately and they settle at the bottom, so the mixture is not the same everywhere.
Sugar and water (homogeneous): The sugar dissolves completely. The mixture looks the same throughout and we cannot see the sugar separately.
Q5. Discuss the importance of separating mixtures in the context of recycling and waste management.
Answer: Our waste is a mixture of many things such as paper, plastic, glass and metal. These cannot be recycled together, so they must be separated first.
Separating lets us take out the useful materials and use them again, which saves natural resources. It also means less waste goes to landfills, so there is less pollution. In recycling plants, magnets are used to pull out iron and steel from the rest of the waste. This is called magnetic separation.
Q6. What are the characteristics of a homogeneous mixture? Explain with an example how a homogeneous mixture can be separated into its components.
Answer: A homogeneous mixture looks the same all through. Its components are mixed evenly and we cannot see them separately, and they do not settle down on standing.
Example: salt dissolved in water. To separate it, we heat the salt solution. The water changes into vapour and goes away (evaporation), and the salt is left behind in the vessel. If we also want the water back, we can use distillation, in which the vapour is cooled and collected as pure water.
Q7. Look at the image given below. Four beakers A, B, C and D contain water kept at different temperatures. The same amount of salt is added to each beaker. A stirrer is dipped in all the beakers except beaker C. The beaker in which salt will dissolve at the fastest rate is
(a) A
(b) B
(c) C
(d) D
Answer: (b) B
Two things make a solid dissolve faster: a higher temperature and stirring. Beaker B is at the highest temperature (70 °C) and it also has a stirrer, so the salt dissolves fastest there. Beaker C has no stirrer, and beakers A and D are at lower temperatures.
Q8. Observe the two images given below. The composition of substances
(a) is fixed in A but not fixed in B
(b) is not fixed in A but is fixed in B
(c) is not fixed in both A and B
(d) is fixed in both A and B
Answer: (b) is not fixed in A but is fixed in B
A is tea, which is a mixture of water, milk, tea leaves and sugar. We can add more or less of each, so its composition is not fixed.
B is aluminium foil, which is made of only one substance, aluminium. Its composition is always the same, so it is fixed.
Q9. Samvit took two beakers A and B having equal quantities of water in them. To A, he added some cubes of sugar, and to B, some oil was added. He stirred the two mixtures and kept them still for some time. Based on his experiment, select the correct option.
(a) The components of A can be easily separated.
(b) The components of B can be easily separated.
(c) The components of both A and B can be easily separated.
(d) The components of neither A nor B can be separated.
Answer: (b) The components of B can be easily separated.
In beaker A the sugar dissolves fully in the water and cannot be seen, so the two cannot be separated just by letting it stand. In beaker B the oil does not dissolve in water. On standing, the oil floats and forms a separate layer on top, so it can be easily removed, for example with a separating funnel.
Q10. A student took three beakers A, B and C, each having 100 mL of water in it and maintained at 25 °C. To these beakers, sulphur powder, salt and sugar were added in varying amounts respectively. The observations of the experiment are tabulated below.
| Beaker | Number of spoons of substance added | Observation |
|---|---|---|
| A | 1 | Sulphur powder settled at the bottom |
| B | 6 | Salt got deposited at the bottom |
| C | 4 | Sugar got deposited at the bottom |
Based on the experiment, it can be concluded that
(a) different substances dissolve in different amounts in water to form a saturated solution
(b) different substances dissolve in the same amount in water to form a saturated solution
(c) any substance can be dissolved in water to form a saturated solution
(d) no substance can be dissolved in water
Answer: (a) different substances dissolve in different amounts in water to form a saturated solution
In the same 100 mL of water at the same temperature, sulphur did not dissolve at all, salt dissolved up to 6 spoons and sugar up to 4 spoons before settling at the bottom. This shows that each substance has its own limit for dissolving in water. When no more will dissolve, the solution is said to be saturated.
Q11. Read the statements I, II and III given below.
I. A mixture is made up of two or more substances present in a fixed ratio.
II. The components of a mixture are separated to remove the undesirable substances from them.
III. The substances present in a mixture are called compartments.
Which of the following statements are INCORRECT?
(a) I, II and III
(b) II and III
(c) I and III
(d) I and II
Answer: (c) I and III
Statement I is wrong, because the substances in a mixture are not in a fixed ratio; they can be mixed in any amount.
Statement III is wrong, because the substances in a mixture are called components, not compartments.
Statement II is correct, as we do separate mixtures to remove unwanted substances.
Q12. Observe the image given below. The medium in which fishes survive is an example of
(a) heterogeneous mixture
(b) homogeneous mixture
(c) pure liquid
(d) pure gas
Answer: (b) homogeneous mixture
Fish live in water that has oxygen and some mineral salts dissolved in it. These dissolved substances cannot be seen separately and are spread evenly through the water, so it is a homogeneous mixture. It is not a pure liquid, because other substances are dissolved in it.
Related Study Material on Extramarks
- CBSE Important Questions Class 6 Science Chapter 1
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- CBSE Important Questions Class 6 Science Chapter 5
- CBSE Important Questions Class 6 Science Chapter 6
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Q.1 What is the main function of the roots in aquatic plants?
(a) Hold the plant in place
(b) Absorb nutrition
(c) Prepare food
(d) Store food
Marks:1
Ans
(a) Hold the plant in place
The main function of roots in aquatic plants is to hold the plant firmly at its place. They are also reduced in size. This is different from the roots of terrestrial (land) plants, where the main function of the roots is to absorb nutrients.
Q.2 Which of the following has webbed feet?
(a) Yak
(b) Duck
(c) Octopus
(d) Sheep
Marks:1
Ans
Webbed feet help ducks to swim in water.
Q.3 Which of the following structures is used by dolphins for breathing?
(a) Gills
(b) Blowholes
(c) Scales
(d) Mouth
Marks:1
Ans
Dolphins do not breathe through gills like other aquatic animals. Instead, they breathe through blowholes which are present on the upper parts of their heads. They come to the surface of the water to breathe in the air and can stay in water for a long time without breathing.
Q.4 Humans and whales are both mammals that breathe air into their lungs. Then why can’t humans live underwater as whales do?
Marks:3
Ans
Whales have a special respiratory organ called a blowhole, located right on top of their heads. While swimming or resting under the water, a blowhole allows them to take breaths by exposing only the top of their heads to the air. A whale inspires more oxygen in a single breath than a human. For this reason, they are able to hold their breath and stay underwater for a longer period of time than human beings.
Q.5 Write and explain the adaptation in fishes due to which they are able to
a. move faster through water
b. move forward, turn, keep an upright position, or stop.
Marks:3
Ans
a. Streamlined body: The body of fish is long and pointed at both ends. The streamlined bodies allow most fishes to move faster in water with less resistance.
b. Fins and tail: The flat fins and tails of fishes help them to change directions underwater. For instance, the back fin helps the fish swim in a straight path while the tail fin helps it to move forward swiftly. It also helps in balancing the body in water.