Air is not a compound, but a mixture of a variety of gasses. The air in the atmosphere consists of nitrogen, oxygen, which is the life-sustaining substance for animals and humans, carbon dioxide, water vapor, and small amounts of other elements (argon, neon, etc.). Higher in the atmosphere air also contains ozone, helium, and hydrogen. People can only clearly notice the presence of air when the wind blows.
Air Is Considered A Mixture For The Following Reasons:
- Air can be divided into its components like nitrogen, oxygen, argon, and carbon dioxide by the process of fractional distillation of liquid air.
- Air shows the properties of all the gases present in the atmosphere. For example, Oxygen is a good follower of combustion. Hence air also is a good follower of combustion.
- Air does not have a fixed formula.
- Air has a variable composition because air at various places contains different amounts of gases.
- Heat or Light energy is neither absorbed nor released when air is prepared physically by mixing the required amount of gases.
- The mixture does have a pointed boiling point. It holds good in the case of liquid air.
What Does Air Consist Of?
The air we breathe includes most of the following gases:
- Nitrogen (N2): 78%
- Oxygen (O2): 20%
- Noble gasses: 1%
- Carbon dioxide (CO2): 0.03%
- Water vapor (H2O): 0.97%
The amount of water in the air highly varies. When large amounts of water are present in the air other elements are present in lower amounts. The amount of water in the air can grow up to 4%. The lowest percentage of water in the air is 0,5%. Water presses present gases closer together so that they can take up enough space.
When the amount of water in the air is very low, the air is named ‘dry’. The weight of 22,4 dm3 of dry air is 28,96 grams. When the air consists of sufficient amounts of water it is called humid. Humid air is lighter (less dense) than dry air.
Apart from the elements that have been summed up earlier, other elements are also present in the air. However, the percentages of these elements are very low. Aerosols can be found in the air. These are dust particles that are blown off the earth’s surface by wind, or emitted during volcanic activity. When burning processes take place, ashes and grime particles also end up in the air.
The composition of air varies greatly with height. Over ninety kilometers above the earth’s surface oxygen molecules fall apart and only oxygen atoms are left. Over one hundred kilometers above the earth’s surface, nitrogen molecules also decompose. At this height, the air does not have the composition we know. The atmosphere is completely different there.
What Are Gases?
All chemical elements can be found in a lot of different states (phases). One of these stages is the gaseous phase. Apart from gaseous an element can also be solid or liquid. Water is called ice when it is solid, it is wet when it is liquid, and when it is gaseous it endures merely as gas or steam.
When temperatures grow, the molecules of a consequential part, causing the substance to become gaseous and less visible. This stage change causes air to be invisible.
When temperatures fall air molecules are more convenient together and a substance finally becomes solid. The temperatures at which each ‘phase change takes place to alter for each substance.
Where On Earth Do We Find Air?
We can state that air can be detected everywhere on earth except where there is water. Air is even spotted in the surface layer of the earth; in the soil.
Air is not only located on earth, it is also situated around the earth in an air layer hailed the atmosphere. The atmosphere can be divided up into different layers depending on temperature and height. These lines are not clearly divided by straight borders; they constantly overflow one another.
The first layer of air, which is located closest to the earth is called the troposphere. This layer is 11 kilometers in height. When moving up in the troposphere temperatures decline six or seven degrees per kilometer. Consequentially the weather on earth is primarily determined by circumstances within the troposphere.
The upper layer of the troposphere is hailed the tropopause. Near the Antarctic, the tropopause layer is situated eight to ten kilometers above the earth. However, at the equator, the tropopause layer is detected at seventeen to eighteen kilometers above the earth.
The second layer of air above the troposphere is hailed as the stratosphere. Temperatures stop declining in the lower part of this layer. The temperature is around -55 degrees Celsius here. In the higher stratosphere temperatures are increasing to zero degrees Celsius at forty-seven kilometers above the earth.
Within the stratosphere, solar radiation builds ozone (O3) from oxygen (O2), between twenty and forty kilometers above the earth’s surface. This reaction causes this part of the stratosphere to be attributed to the ‘ozone-sphere’. The upper part of the stratosphere is hailed as the stratosphere.
The third layer of air is hailed as the mesosphere. This layer can be found over fifty-two kilometers above the earth’s surface. The upper part of the mesosphere is hailed as the mesosphere. Within the mesosphere, temperatures are declining once more. Mesosphere temperatures are around -90 degrees Celsius.
The fourth layer of air, the thermosphere is detected over ninety kilometers above the earth. Temperatures rise enormously in this layer, causing the highest temperature to be above one thousand degrees Celsius. The density of air is very low in this layer, therefore the strengths between molecules nearly vanish.
The lightest molecules can depart through the lowest layer of the thermosphere, the exosphere. The exosphere does not have a clear border, because it disappears into space.
The lowest ninety kilometers of the atmosphere are often referred to as the hemisphere because the air composition is fairly constant. All air above this layer is referred to as hydrosphere because the air has a very different composition in this area.
What Types Of Air Are There?
When a large quantity of air has one identical dampness and temperature, it is rated as one separate type of air. The air type must cover a horizontal area of one thousand kilometers. The height of an air type can vary between one hundred meters to coverage of the entire troposphere.
An air type forms when an air mass has been circulating for three to nine days in an area that is located completely above either land or sea and where the wind does not blow. Within this area, the air mass receives its specific properties. Above land, these areas can be deserts or savannas.
As soon as the air leaves the area its specific properties will slowly fade and eventually disappear entirely.
Air types that have received their specific properties in an area above the sea are much more humid than air types that have received specific properties above land. The air types that are shaped above oceans are called marine air types. Air types that are shaped above land are called continental air types.
We can distinguish four separate basic air types, which can all be divided up between marine and continental types:
- Equatorial air. The temperatures lie between 25 and 30 degrees Celsius and its moisture content is high.
- Tropical air. Marine tropical air has high moisture content and a temperature of around 25 degrees Celsius. Continental tropical air has low moisture content and a temperature of over 50 degrees Celsius.
- Polar air. Marine polar air is always humid and is relatively hot in winter and cold in summer. Continental polar air is very dry and cold in winter. Temperatures can fall to below -50 degrees Celsius. In summer this type of air is warm, yet still very dry.
- Arctic air. This type of air is very cold. Marine arctic air is warmer than continental arctic air in winter.
What Is Wind?
The wind is mainly air that is in motion. The air moves as a consequence of different types of air pressure on earth. Wind direction and wind force can vary rapidly. Wind-force is often referred to as cardinal locations.
Wind-force is expressed as a number hailed a Beaufort number, on the Beaufort scale. The wind force is always measured about ten meters above land.
Description of wind speed according to the Beaufort scale
Description – Wind speed(Metres per second)
- Windless: – <1 (Metres per second)
- Little wind: – 1-3 (Metres per second)
- Little wind: – 4-6 (Metres per second)
- Moderate wind: – 7-10 (Metres per second)
- Moderate wind: – 11-16 (Metres per second)
- Rather strong wind: – 17-21 (Metres per second)
- Strong wind: – 22-27 (Metres per second)
- Rough wind: – 28-33 (Metres per second)
- Stormy wind: – 34-40 (Metres per second)
- Storm: – 41-47 (Metres per second)
- Heavy storm: – 48-55 (Metres per second)
- Very heavy storm: – 56-63 (Metres per second)
- Hurricane: – >63 (Metres per second)
Simply put, wind lies because solar radiation warms the earth. Heat and hot air rising, causing the air in the atmosphere to initiate moving. This motion is known as wind. During this passage of air, warm air is transported from the equator to the poles and cold air is transported back to the equator. This aftermath causes the equator to cool down and the poles to lightly warm up to prevent extreme temperatures. Apart from wind, oceans also aid in circulating heat.
Air does not move precisely from the equator to the poles and back, as you might expect. The spinning motions of the earth influence wind directions. Consequentially, the wind that blows from the equator to the North Pole is turned slightly eastwards. The wind that blows from the equator to the South Pole is turned slightly westwards. The wind is consistently called after the direction it comes from. Wind from the equator to the North Pole is called west wind. Hot air that is blown from the equator to the poles freezes down on its way.
On 30o north and south latitude, air falls back to the earth’s surface. Not all air will be blown back to the equator from there.
The wind blows in a circle, called a cell. On earth we can distinguish three kinds of cells:
- The Hadley cell is a cell between the equator and 30o north and south latitude. The wind in this cell that is located near the earth’s surface is called the trade wind.
- The Ferrell cell is located between 30o and 60o north and south latitude. The wind in this cell blows harder in winter. At the 30o latitude border, windfalls and blows towards the poles. At 60o latitude, the air rises and the wind blows back to the 30o latitude border. Not all wind blows back, part of the wind from the Ferrell cell is taken up in the Pole cell.
- The Pole cell is located on the poles, up to 60o north and south latitude. At 60o latitude, the air rises, but above the poles, the air falls. Winds in the Pole cell are usually cold and dry.
This is only an impression of how the wind blows on earth. The earth does not only consist of water, but also of the land. Land influences wind directions. This causes the wind to be able to blow in a different direction in separate regions.
What Is Air Pressure?
Air practices a certain force on objects called air pressure. All air found in the atmosphere presses itself upon the earth as a result of the magnetic attraction force of the earth. Air pressure is practiced upon each object and life form on earth, such as tables, roofs, and houses, but also humans, animals, and plants. You will not notice this air pressure, because there is a force inside your body that creates a pressure equally strong on the air around you. Under a table the pressure equals the pressure on the table, otherwise, it would directly collapse.
Air pressure is defined as the pressure that the total weight of a column of air practices upon a piece of the earth of one square meter (1 m2). The unit of pressure is Pascal (Pa).
The highest air pressure is situated at the bottom of the atmosphere, just above the ground. Higher in the atmosphere the air pressure decreases. On earth you experience the pressure of a large number of air particles; higher in the air there are fewer particles present that practice pressure upon you.
The average air pressure on earth is 1013 hPa. This is not an exact number and as such, it can vary a little bit. People will hardly notice this because their bodies adapt to new air pressures. However, some people are more sensitive to changes in air pressure. For those people, a change in air pressure can cause migraines.