4. Grouping materials WORKBOOK Q-ANS
1 Choose the correct option.
1. Identify the gas that does not dissolve in water.
(a) oxygen (b) methane
(c) carbon dioxide (d) both (b) and (c)
ans: methane
2. Which of the following substances is lustrous?
(a) sand (b) plastic
(c) brass (d) wood
ans: brass
3. Identify the correct statement.
(i) Solids have definite shape but do not have definite volume. (ii) Gases have definite volume but do not have definite shape. (iii) Liquids have definite volume but do not have definite shape. (a) only (i) (b) only (ii)
(c) only (iii) (d) both (i) and (ii)
ans: only (iii)
2 In the following questions, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Read the statements carefully and choose the correct alternative (A), (B), (C) and (D) as given below.
(A) Both A and R are true and R is the correct explanation of the assertion.
(B) Both A and R are true but R is not the correct explanation of the assertion.
(C) A is true but R is false.
(D) A is false but R is true.
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1. Assertion: A substance exists in solid state.
Reason: The molecules of solids can move throughout the volume occupied by the substance.
ans: (C) A is true but R is false.
2. Assertion: An iron nail sinks in water.
Reason: The density of the iron nail is more than water.
ans: (A) Both A and R are true and R is the correct explanation of the assertion.
3 State whether true or false. Correct the false statements.
1. Chalk is soluble in water.
ans: False
Chalk is insoluble in water.
2. Stones and metal keys float on water.
ans: False
Stones and metal keys sink in water.
3. Cotton is soft and iron is hard.
ans: True
4 Classify the following things as transparent, translucent and opaque . (marble, water, frosted glass, glass door, brick, butter paper)
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5 Answer in one sentence.
1. Name five objects that can be made from wood?
ans: Table, chair, door, boat, bed
(answer may vary, accept all correct answers)
2. What are immiscible liquids?
ans: The liquids which do not dissolve in water are called immiscible liquids.
3. How are rough materials different from smooth materials?
ans: Rough materials have irregular surfaces with bumps or ridges whereas smooth materials have plain and even surfaces.
6 Give reasons for the following statements.
1. Sweets are kept in transparent glass containers in sweet shops.
ans: Glass is transparent and can make light pass through it. When sweets are kept in glass containers, it is easy for the customer to select their choice of sweet without touching it.
2. Metals are lustrous, but the iron used in window grills does not shine. ans: The iron used in window grills does not shine because it reacts with air and moisture. This results in rough appearance and reddish brown colour.
7. The arrangement of molecules in three different substances is shown below. Observe
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the figure and identify whether the substances are solids, liquids or gases. Justify your answer.
________________________ _________________________ _________________________ ________________________ _________________________ _________________________ ________________________ _________________________ _________________________ ________________________ _________________________ _________________________
Gaseous substance because the particles are
very far from each other.
Liquid substance because the particles are close but not as close as in solids.
Solid substance
because the particles are very close to each other.
8. Zain, Mira, Tim and Ella were given red chilli powder, butter, kerosene and honey respectively, and were asked to check the solubility of each in water. Design an experiment that they can conduct to identify the soluble substances. ans:
Take four test tubes. Fill 1/3 rd of the test-tubes with water. Add red chilli powder, butter, kerosene and honey respectively in each test tube using a spatula. Shake the test tubes and allow the test tubes to stand for fifteen minutes. Record the results in the following table:
Test Observation Inference
1. red chilli powder + Red chilli powder is seen at the bottom of
Red chilli powder is
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water the test tube. insoluble in water.
2. butter+ water Butter is seen floating on water.
3. kerosene+ water Kerosene forms a separate layer on water.
Butter is insoluble in water.
Kerosene is insoluble in water.
4. honey + water Clear water is seen. Honey is miscible in water.
HOTS
Take a small cotton ball and place it in a tumbler/ bowl filled with water. Observe it for at least 10 minutes. Will it float or sink in water? Why?
ans: The cotton ball will absorb water and sink to the bottom. This is due to increase in the density of the cotton ball after absorbing water.
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