We explain what air is and what it is composed of. Also, what are its physical and chemical properties. Air pollution.
What is Air?
We commonly call air the homogeneous mixture of atmospheric gases that are retained by the gravity of our planet.
Air is a gaseous mixture of utmost importance for life on Earth, since it fulfills the 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 the oxygen necessary for respiration. Furthermore, air allows the hydrological cycle to occur, as it contains water vapor, which produces precipitation through condensation and the formation of clouds.
Air is composed of various gaseous elements, which normally cannot be differentiated or perceived separately. However, is it possible to liquefy air in laboratories (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 pressure and temperature conditions in which these elements are found at the time of making the measurements.
The importance of air 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. However, today, its properties are known in more detail and it is possible to take greater advantage of them.
See also: Air pollution
What is air composed of?
Air is mainly composed of 20.94% oxygen, 78.08% nitrogen, 0.93% argon 0.035% carbon dioxide and 0.40% water vapor, these being its predominant components.
Other elements present in the air, although in a minority, are neon (0.0018%), helium (0.0005%), methane (0.00017%), krypton (0.00014%), hydrogen (0.00005%) and ammonia (0.0003%).
Physical and chemical properties of air
Air varies according to its location in the following layers of the atmosphere: troposphere, stratosphere, mesosphere and thermosphere. The higher it is, the less pressure and the less weight it will have air, since the heavier elements it can contain are attracted more strongly by the Earth's gravity.
In general terms, air is less heavy and has a lower density than water (air has a density of 1.225 kg/m3 at about 20 ºC temperature). It is transparent, colorless, odorless and tasteless except when contaminated with some particular substance.
Air has no volume of its own since it is a gas and is incapable of existing in a vacuum. In addition, it is a good conductor of heat.
The chemical reactions that a mass of air can undergo depend on the chemical properties of the constituent components. In this sense, air has approximately constant proportions of some components, but it can also have pollutants or concentrations of some substances at high levels, depending on where that air mass is located, under what conditions it is, etc.
air pollution
Air pollution occurs when there are solid particles suspended in it, or when different gases that are naturally present in its composition exceed certain levels, and are then considered pollutants. There may even be a mixture of both.
Just like water or earth, air It is a recipient of substances emitted during industrial processes urban or waste that we release into the environment. This often brings serious complications such as acid rain (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 in the ozone layer in the stratosphere, allowing the direct passage of solar radiation).
Some of the main known air pollutants are:
- Gases produced by the combustion of fossils Carbon dioxide, carbon monoxide and sulfur dioxide are obtained as a result of the burning of fossil fuels such as oil, gasoline or coal.
- Chlorofluorocarbon compounds Known as CFCs, they are some of the most harmful domestic and industrial gases for the ozone layer. Due to this, since 1960 its necessary replacement by other less harmful gases has been noted (when applied in aerosols and refrigeration compressors).
- Methane It is a gas with a foul smell that is a product of the decomposition of organic matter. It is present in the feces of humans and animals, as well as in swamps and other areas of continuous decomposition of living matter. A large source of methane in the atmosphere, which exceeds levels beyond normal, is the waste from large herds of livestock animals (cows, pigs, etc.). They constitute one of the gases that cause the greenhouse effect and global warming.
- Ozone Although ozone is found naturally in the stratosphere, it can be found artificially in other lower layers, where it does not act as a beneficial agent but as a pollutant.
- Volcanoes and other natural disasters When volcanoes erupt, they expel enormous amounts of dust, smoke and combustion gases into the atmosphere, generating numerous air pollutants.
Continue in: Air pollution
References
- Physics. Theoretical-practical course on physical foundations of engineering. A. Llopis, FJ Gálvez, C. Rubio, R. López, collaboration with JM Bravo. p. 456. Polytechnic University of Valencia. (Google Books)
