Air and Atmosphere - Class VI

The Earth's atmosphere is composed of approximately 78 percent nitrogen gas, making it the largest reservoir of nitrogen on the planet.

As air rises, it encounters lower atmospheric pressure and expands. This expansion requires energy, which is taken from the air's internal energy, causing the temperature to drop (adiabatic cooling).

As air sinks, it is compressed by the increasing atmospheric pressure. This compression adds energy to the air parcel, causing its temperature to rise (adiabatic warming).

The density of air at sea level is approximately 1.225 kg/m^3, which is equivalent to 1.225 grams per liter. 1.3 grams is the standard approximation used in many textbooks.

It is true that 70% or so of the Air is nitrogen but that it needs to be the largest reservoir. Nitrogen is an essential part of most living organisms. Most of the bodily fluids and enzymes have nitrogen in a bonded form. This is true even in the case of plants. So, the correct answer is "Air".

When two unsaturated air masses with different temperatures mix, the resulting mixture can become saturated if the mixing process crosses the saturation curve on a psychrometric chart.

"Ozone hole" means thinning of the ozone layer.

Scuba divers use a mixture of gases to avoid nitrogen narcosis and oxygen toxicity at high pressures. Helium is often used to dilute the mixture because it is inert and less soluble in blood than nitrogen.

The nitrogen molecules present in the air can be converted into nitrates and nitrites by nitrogen fixation.

Reformation of ozone in stratosphere is powered by UV radiation.

The part of the atmosphere which contains constant gases with a known composition called homo-sphere.

Plant consume carbon dioxide, water and other nutrients to make their own food.

Solid oxygen is a clear substance with a light sky-blue colour. Oxygen gas is a colourless gas without taste or odour. Oxygen toxicity is a condition that results from the harmful effects of breathing molecular oxygen $(O _2)$ at elevated partial pressures. This causes hyperoxia, an excess of oxygen in body tissues.

Oxygen is produced by plants by the process of photosynthesis,

Plants plays a very important role in the oxygen cycle as plants create the majority of oxygen we breathe through the process of photosynthesis. In this process plants use $CO _2,$ sunlight and water to create energy. In this process they also create oxygen which they release into the air.

Plants also consume oxygen for respiration.