Class 6 Science Chapter 11 Question Answers - Air Around us

Short Q & A:

Q1: What happens when air comes in contact with a cool surface?
Ans: When air comes in contact with a cool surface, the water vapor present in the air undergoes condensation due to the lower temperature of the surface. This condensation forms droplets of water on the cool surface.

Q2: Why do you think mountaineers carry oxygen cylinders with them while climbing high mountains?
Ans: There is less oxygen at high places like mountains, so they carry oxygen cylinders with them to breathe there.

Q3: Why do you feel suffocation in a closed room, where some material is burning?
Ans: Burning of some materials releases smoke that contains few gases and fine dust particles that are harmful, thus we feel suffocation in a closed room, where some materials are burning.

Q4: Why are there long chimneys in factories?
Ans: Chimneys in factories serve the crucial purpose of venting harmful gases and smoke produced during industrial processes. However, their function extends beyond merely removing pollutants from immediate proximity. Chimneys are designed to release these emissions high into the atmosphere, where they disperse more effectively, minimizing their impact on local air quality and human health.

Q5: Air is necessary for combustion. Explain the statement.
Ans: Fix two candles in the middle of a container containing water. Light both candles. Now cover the candles with an inverted transparent glass, and you will observe that the candles go off. This happens because of the absence of air. Thus we can say that air is necessary for combustion.

Q6: Air occupies space. Explain the statement.
Ans: Blow a balloon, air from your body enters the balloon and it gets bigger because air occupies space.

Q7: When the open mouth of an empty bottle is tilted in a bucket filled with water, we see bubbles coming out of it. Explain the phenomenon.
Ans: The bottle contains air so when it was titled air came out in the form of bubbles.

Q8: What is air made up of?
Ans: Air is made up of a mixture of gases like - Nitrogen, oxygen, carbon dioxide, water vapour, dust particles and other gases.

Q9: Air contains dust particles, while inhaling air we also inhale dust particles. Give a reason in support of the statement, whether it is true or false.
Ans: False, While our nasal passages indeed filter out larger dust particles, it's important to note that some fine particles can still bypass these defenses and enter our respiratory system. So, while our respiratory system has mechanisms to mitigate the impact of dust particles, it's not entirely accurate to say that we don't inhale any dust particles.

Q10: Why should we not breathe through our mouths?
Ans: If we breathe through our mouth then dust particles present in the air will enter our bodies and cause harmful diseases.

Q11: Draw a diagram showing the composition of air in the atmosphere.
Ans:

Q12: How does an organism living in soil breathe?
Ans: Through air present in soil.

Q13: How can you show that air is dissolved in water?
Ans: Take water in a pan and heat it. After sometimes just before it boils we can observe some bubbles at the inner surface of the pan. This is because of the air dissolved in water.

Q14: Why an animal living in the soil does come out of the soil for respiration in the rainy season?
Ans: When it rains heavily, water fills up all the spaces occupied by the air in the soil. Therefore organism living in soil has to come out for respiration.

Q15: Why does a lump of cotton wool shrink in water?
Ans: A lump of cotton wool shrinks in water because water molecules fill the spaces between the fibers of the cotton wool. This process, known as capillary action, displaces the air that was initially occupying those spaces, resulting in the shrinkage of the cotton wool.

Q16: List at least five activities that are possible due to the presence of air.
Ans: Respiration, burning, photosynthesis, movement of aeroplanes and parachutes, generation of electricity by windmills.

Q17: How do plants and animals help each other in the exchange of gases in the atmosphere?
Ans: Plants and animals help each other in the exchange of gases in the atmosphere Plants take carbon dioxide to prepare food and release oxygen during daytime. This oxygen is taken in by animals and carbon dioxide is released. Thus, plants and animals help in maintaining a balance of oxygen and carbon dioxide.

Long Q & A:
Q1: Explain the role played by air in the lives of humans, animals and plants.
Ans: Living things cannot live without air. We can survive on earth because of the atmosphere only. Plants prepare their food by the process of photosynthesis which is possible because of air. They use carbon dioxide gas in air and release oxygen that is utilized by human and animals to breathe. Air is necessary for the combustion, and flying of aeroplanes and birds. Thus it is well said that 'Air is life'.

Q2: What is the importance of water vapour in air?
Ans: When air comes in contact with a cool surface, it condenses and forms tiny drops of water on the cooled surfaces. The presence of water vapour in the air is important for maintaining the water cycle in nature.
This is because it is water vapour present in the air which rises high in the sky along with hot air, get cooled, condenses to form clouds and then brings rain on the earth.

Q3: Explain briefly carbon dioxide gas and its properties.
Ans: Carbon dioxide is a colourless and odourless gas. It is soluble in water. It neither burns nor supports burning. CO₂ extinguishes a burning fire. Plants and animals consume oxygen for respiration and produce CO₂ which is necessary for photosynthesis. It is an important greenhouse gas.

Q4: What are the uses of air?
Ans: Air is useful to human beings in many ways. Some of the important uses of air are as follows:

• It is used for breathing purpose.
• It is used for burning fuels to make fire.
• It helps the birds, bats and insects in flying.
• It plays an important role in the water cycle in nature.
• Compressed air is used in tyres of various kinds of vehicles.
• It also helps in the dispersal of seeds and pollens of flowers of several plants.

Q5: Why the animals living deep inside the soil come out during heavy rains?
Ans: The air is present in spaces between particles of soil. Animal living inside the soil get oxygen for breathing (or respiration) from the air present between the soil particles. However, when it rains heavily water fills up the spaces occupied by the air in the soil.
In this situation, the animals living inside the soil have to come out of the soil to obtain air for breathing. For example, the earthworms come out of the soil only during heavy rains.

Q6: Why we must always breathe in through our nose and not by our mouth?
Ans: We inhale air when we breathe through our nostrils. We also know that air contains dust particles. To prevent dust particles from getting into the respiratory system, fine hair and mucus are present inside the nose.
Since our mouth does not contain the above-discussed barriers of dust, so if we breathe through it, dust particles may enter in our respiratory tract. This is why breathing through mouth is not suggested.