Air and Atmosphere: ICSE Class 6 Solutions

Air and Atmosphere: ICSE Class 6 notes and solutions

Question: State what would happen, if the air above the earth contained mainly oxygen and no nitrogen.

Answer: Nitrogen is utilised by plants for their growth and development. It is converted to soluble nitrogenous compounds in the soil in the presence of air and moisture. They are absorbed by plants and utilised as plant proteins. With no nitrogen, plants will not be able to survive on earth.

If the air above the earth contained mainly oxygen, the risk of fires would increase a great deal This leads to difficult in extinguishing fires. It would reduce the amount of oxygen and increase CO2 considerably.

Question: State the utility of oxygen for respiration in a) Living organisms b) Plants

a) Respiration in living organisms: It is a process whereby living things

• 1) Use oxygen from their air to ozidize food substances mainly glucose in their body cells.
• 2) Release energy in the form of heat.
• 3) Carbon dioxide and water vapour are also produced and released in the exhaled air.

b) Respiration in plants:

• 1. Plants respire during the day and night.
• 2. Plants respire through tiny pores on the surface called stomata.
• 3. The stomata help in taking in the oxygen and giving out carbon dioxide.
• 4. Plants do not perform bodily activities and hence need less energy than animals. The rate of respiration in plants is thereby slower than in animals.

Question: Compare respiration and combustion – both involving oxygen in air.

Respiration: It is a process in which livng organisms use oxygen from air to oxidize food substances mainly glucose, in their body cells. Release energy in the form of heat.

Combustion: Combustion or burning involves oxidation of substances like fuels with oxygen or air. Release energy in the form of heat and light.

Question: Explain the importance of carbon dioxide for (a) Photosynthesis (b) warming the earth’s environment. State what would happen if excess carbon dioxide as a pollutant is released into the atmosphere.

Answer: a) Photosynthesis in plants:

• 1. During photosynthesis which occurs during daytime, plants manufacture their own food.
• 2. They absorb carbon dioxide from the air and water in the presence of sunlight and chlorophyll is changed into glucose and oxygen is released out.
• 3. Hence oxygen in air is renewed by photosynthesis, and therefore the amount of oxygen in air does not get depleted or removed from air.

b) In the greenhouse effect (for warming the earth)

• 1. Earth gets heated up because of infrared, visible ray & ultra violet rays.
• 2. Carbon dioxide in the air allows UV rays to pass through but prevents the infrared rays from being radiated out of earth’s surface. It results in warming the earth’s environment.

If excess carbon dioxide is released into the atmosphere, it will result in rise in temperature leading to global warming.

Question: State in brief how water vapour in the atmosphere determines the climatic conditions.

Answer: Water vapour in the atmosphere determines climatic conditions by:

• 1. Minimizing the rate at which evaporation takes place.
• Condensation of clouds into rain, producing mist etc. and thereby dropping the temperature

Question: Give a reason why two different rare (inert) gases find application in advertisement signs and fluorescent bulbs.

Answer:

• 1. Neon is used in advertisement signs because when current is passed through this gas at low pressure, a brilliant red glow can be seen. This colour can be changed by adding mercury and argon.
• Xenon is used in fluorescent bulbs and lasers because it emits intense white light in discharge tubes.

Question: A mixture has variable composition. Give reasons why air is considered a mixture and not a compound.

Answer: Air is a mixture and not a compound because:

• 1. Air does not have a formula like a mixture, while compounds have a fixed formula.
• 2. When air is formed by gases, there is no energy change.
• 3. Properties of air are found to be the average properties of its constituents. Therefore, it has no definite properties.
• 4. Components of air can be physically separated.

Question: State a reason why there is a balance in the amount of carbon in the air, even though carbon dioxide is released into the atmosphere by various processes.

Answer: In photosynthesis, green plants manufacture their own food by absorbing carbon dioxide in the air and make food in the presence of chlorophyll and sunlight. Oxygen is released into the atmosphere, which maintains the composition of air and does not increase the amount of carbon dioxide in air.

Question: Name three different appliances where air is utilized.

Answer: Appliances, where air is utilized, are:

• 1. Vehicles run on tyres inflated with air.
• Brake mechanisms work on compressed air.
• Pumps and siphons work on air pressure