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Question
Why does a lump of cotton wool shrink in water?
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Solution
A lump of cotton wool shrinks when immersed in water. This is because air present in the cotton wool escapes. Thus, the volume of the cotton wool decreases.
RELATED QUESTIONS
Match the statements in List 1 with the correct answers in List 2
| List 1 | List 2 | ||
| 1 | An impurity in air | A | Water vapour |
| 2 | The component of air which supports combustion | B | Respiration |
| 3 | The inert component in the air slightly soluble in water | C | Rare gases |
| 4 | The component of air which minimizes the rate of evaporation | D | Sulphur dioxide |
| 5 | The process which involves oxidation of food substance in living organisms | E | Helium |
| 6 | The component of air which finds application in observation balloons | F | Carbon dioxide |
| 7 | The process which involves oxidation of substances, liberating heat and light energy | G | Combustion |
| 8 | The component of air which is heavier than air and fairly soluble in water | H | Nitrogen |
| 9 | The process by which atmospheric carbon dioxide is absorbed by plants resulting in the formation of carbohydrates | I | Photosynthesis |
| 10 | The component of air which is lighter than air and less than 1% in air | J | Oxygen |
Name the following:
A process which removes carbon dioxide from the air.
State whether the following statement is ‘true’ or ‘false’. If false write the correct statement.
Photosynthesis is a process by which green plants prepare their own food in the presence of sunlight and chlorophyll.
List out the uses of carbon dioxide.
How do plants and animals maintain the balance of oxygen and carbon dioxide in the air?
Which gas is essential for burning?
Air also contains a small amount of carbon-di-oxide, water vapour, and some other gases like argon,
______ is used as a substitute for compressed air in tyres.
The solid form of CO2 is called dry ice which undergoes condensation.
Observe the picture given in figure carefully and answer the following questions.
- What is covering the nose and mouth of the police man?
- Why is he putting a cover on his nose?
- Can you comment on air quality of the place shown in the figure?
