Air refers to the earth's atmosphere. The air present in the earth's atmosphere is a homogeneous mixture of gaseous substances of 78% nitrogen and 21% oxygen, water vapour (variable), 0.9% argon, 0.4% carbon dioxide approximately, and trace gases. Many other gases like hydrogen, neon, helium, methane, etc., are also present in the air in minimal amounts. Air can be separated into its components in special units, employing distillation. The shape and volume of air are not definite, but a shimmering in hot air can be seen.
Oxygen, the most crucial element of air, is essential for respiration and combustion. It is also a significant component of organic molecules that constitute a living organism with carbohydrates, proteins, and fats. Oxygen is not just essential for life sustainability but also for its creation.
Carbon dioxide is a trace gas concentrated with 0.4% of its constitution. This is produced by respiration and through organic decomposition. Increasing amounts of carbon dioxide leads to air pollution.
Nitrogen is the most abundant, pure component of air. It is present in living organisms in classes of nucleic acids and amino acids. Nitrogen is applicable in medicine, having a primary usage in various antibiotics and drugs.
Argon, the third most abundant element in the atmosphere, is a noble gas. In medicine, argon is used as a blue laser to often cure eye flaws and tumours.
Water vapour contributes to the greenhouse effect by absorbing and emitting radiation. It can be used as a lifting gas as its density is lower than air. Dust particles originate from volcanic eruptions or soil or pollution of air.

Plants replace the oxygen in the atmosphere as they take in carbon dioxide and let out oxygen during photosynthesis. The plants take in carbon dioxide and water during photosynthesis and produce glucose.
The pants also consume oxygen for respiration, but they produce large amounts of oxygen through photosynthesis. This is why the plants are called the producers of oxygen. Plants and animals thus maintain the oxygen and carbon dioxide levels in the atmosphere through respiration and photosynthesis. Hence, we know that the dependence of plants and animals are interrelated.
In our environment, humans and other living organisms can survive because of the available oxygen. Humans could not possibly survive on this earth without oxygen. There is no substitute for oxygen for healthy living. But in due course of time, even the available oxygen in the atmosphere might just run out due to continuous usage. Hence, a constant replacement is necessary. This replacement is possible only because humans and animals inhale the oxygen released by plants and release carbon dioxide, which the plants further inhale during photosynthesis. A proper ecosystem exists only when one is compensated with the other. It becomes a cycle. Once the process is broken, no ecosystem would co-exist for one organism or living creature with another. This is how oxygen and carbon dioxide balance is maintained in the atmosphere. Therefore, we must grow more and more plants to maintain the balance.

Plants and animals living in the soil absorb the required amount of oxygen through soil by using the air present in the spaces between soil particles. However, when it rains heavily, the air in the soil is filled by water, and there is no air present in the ground for respiration. During these times, the animals living under the soil are forced to come out to obtain air and breathe. For example, earthworms live under the soil, and they come out of the soil only during heavy rain as there is no space or air left inside the ground to breathe. Many other animals live under the soil, digging burrows and mining tunnels under the earth. These burrows and tunnels create a room for air to circulate freely in soil by which the animals living under the soi can breathe. Also, a plant's root under the earth gets air for respiration through these air particles present in the ground. 

On the other hand, plants and animals living in the water (aquatic plants and animals) absorb the required oxygen from water. The plants and animals living in water absorb oxygen by diffusion through the gills or by the body surface. The water bodies like lakes, ponds, rivers, and seas have dissolved air. Hence these aquatic plants and animals use the oxygen present in the water to breathe.

The major takeaway is that any living being or living organism requires air to breathe and survive on this planet. Air can be used for various other purposes, such as to make fire for cooking or generating heat or light. Fuel cannot burn without the presence of oxygen in the air. Compressed air can be used for filling the tires of trucks, cars, bicycles, airplanes, etc. Since the air around us is essential for our existence, we must not pollute it. Air pollution challenges have been felt throughout. But only upon the reduction of air pollution, the effects of air pollution and its damage to the environment can be reduced. Combustion or the usage of fossil fuel amounts to an increase in pollution. To endorse and promote an environmentally friendly and sustainable livelihood, we must ensure to keep the air around us clean as we are evidently dependent on air for survival. 

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1. How will you prove that air supports burning?

The experiment of a burning candle can be used to prove that air supports burning. Do this experiment in the presence of an adult supervisor. Place a burning candle on a surface. Now, place an inverted glass over the candle. You will see that the fire will be extinguished. This experiment could be proof that combustion is supported by air.

2. Are the NCERT solution book of class 6 enough to score good marks in the board exam?

Studying only with the solution book would not be essential enough to gain all the required knowledge. Though these solution books follow the NCERT pattern and provide a series of crucial questions and answers, it is recommended to first thoroughly read the textbook. If the texts books are read thoroughly, then these solution books would be sufficient for continuous practice.

3. How would you prove that air dissolves in water according to Chapter 15 of class 6 Science NCERT solutions?

An experiment could be used here to show that air dissolves in water. A glass of water could be used here for the investigation. Taking a glass filled with water and heating the water would produce bubbles in the water. The bubbles in the water are being formed even before the water reaches the boiling point. Hence, it is proved that air is dissolved in the water.

4. Is it essential to solve all the examples given in the class 6 NCERT solution book? 

Yes, it is essential to solve all the examples in the NCERT class 6 solution book as they would help you know the pattern of the questions asked in the exams. These examples are relevant to the content studied in the NCERT textbooks. Practising these examples thoroughly might help you score good marks in your board examination.