What is the air?

We explain what the air is and what it is made of. In addition, what are its physical and chemical properties. Air pollution.

1. What is the air?

We commonly call air the homogeneous set of atmospheric gases that are retained by Earth’s gravity around our planet.

The air is a gaseous layer of utmost importance for life on Earth, since it fulfills functions of protection from solar rays and other foreign elements such as meteorites . In addition, it provides the chemical dynamics of the planet with a set of essential elements of a gaseous nature, such as oxygen for respiration , and allows the hydrological cycle to occur.

The air is composed of various gaseous elements, which normally cannot be differentiated or perceived separately. However, it is possible to liquefy the air in laboratories , that is, make it liquid , and proceed to separate its components. In this way, many of the elements used in the chemical industry are obtained. Its properties and composition vary according to the height and the land region where it is measured.

Its importance was perceived by man since ancient times, when it was considered one of the four basic elements of nature , along with fire, water and earth. Today, however, we have a much better understanding of him than ever before.

2. What is the air made of?

The air is composed of a mixture of gases , of which nitrogen, oxygen and argon are the most predominant (78.08%, 20.94% and 0.93% respectively). It also has a percentage (0.035%) of carbon dioxide and water vapor (approximately 0.40%).

Other elements present in the air, although minority, are neon (0.0018%), helium (0.0005%), methane (0.00017%), krypton (0.00014%), hydrogen (0.00005%) and ammonia (0.0003%).

3. Physical and chemical properties of air

The air varies according to its location in the four layers of the atmosphere : troposphere, stratosphere, mesosphere and thermosphere. The higher you are, the less pressure and less weight the air will have , since the heavier elements are attracted more strongly by gravity.

In general, the air is less heavy and has a lower density than water (the air has a density of 1,225 kg / m ³ at a temperature of 15 ° C). It is transparent, colorless, odorless and tasteless , except when it is contaminated with a particular substance.

The air has no volume of its own, since it is a gas, and is unable to exist in a vacuum. In addition, it is a good conductor of heat.

4. Air pollution

Air pollution occurs when there are solid particles suspended in it or gases other than those that are naturally present in its composition. There may even be a mixture of both.

Just like water or land, the air is a receiver of the substances emitted during industrial , urban or waste processes that we release into the environment , which often brings serious complications such as acid rains (the water cycle is contaminated by the reaction with corrosive or poisonous gases in the air), respiratory diseases (for humans and animals) or the deterioration of the layers of the atmosphere (such as the decrease of the ozone layer in the stratosphere, allowing the direct passage of solar radiation).

Some of the main known air pollutants are:

• Fossil combustion gases . Like carbon dioxide, carbon monoxide and sulfur dioxide, the result of burning fossil fuels such as oil , gasoline or coal.
• Chlorofluorocarbons . Known as CFCs, they are some of the most harmful domestic and industrial gases for the ozone layer that exist, and since 1960 their necessary replacement in aerosols and refrigeration compressors with other less harmful gases has been noted.
• Methane . A disgusting smell gas product of the decomposition of organic matter, present in the feces of human beings and animals, as well as in marshes and other areas of continuous decomposition of living matter. One of the great sources of methane in the atmosphere, at levels beyond normal, are the large herds of breeding animals (cows, pigs, etc.). It is one of the gases causing the greenhouse effect and global warming .
• Ozone . Although ozone is naturally found in the stratosphere, it can be found artificially in other lower layers, in which it does not act as a beneficial agent but as a contaminant.
• Volcanoes and other natural disasters . Volcanoes throw huge amounts of dust, smoke and combustion gases into the atmosphere, causing an unpredictable pollution effect .