What is Air?

Air is the invisible mixture of gases that surrounds Earth. It contains important substances, such as oxygen and nitrogen, that most species need to survive. Air has an indefinite shape and volume. It has mass and weight, because it is matter. The weight of air creates atmospheric pressure¹².

What is the weight of Air?

The weight of air depends on the density and volume of air. The density of air, in turn, depends on the temperature, pressure, and humidity of the air. The density of dry air at sea level at 15 °C (59 °F) and 101.325 kPa (14.7 psi) is approximately 1.225 kg/m³ (0.0765 lb/ft³)³. To find the weight of a given volume of air, you have to multiply its density by its volume. For example, a cubic meter of air at the same conditions will weigh 1.225 kg (2.7 lb), while a cubic foot of air will weigh 0.0807 lb (36.6 g)⁵⁶.

What is the molecular mass of Air?

Molecular mass of air = (x1 x M1) + (x2 x M2) + … + (xn x Mn)

where x is the mole fraction and M is the molecular mass of each gas in air. The main gases in dry air are nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2), and others. The molecular mass of each gas can be found by multiplying its atomic mass by the number of atoms in its molecule. For example, the molecular mass of nitrogen gas (N2) is 2 x 14.0067 = 28.0134 g/mol.

Using the data from the web search results, the molecular mass of dry air can be estimated as follows:

Molecular mass of dry air = (0.78 x 28.0134) + (0.21 x 31.999) + (0.009 x 39.948) + (0.0004 x 44.01) + (0.00001818 x 20.18) + (0.00000524 x 4.003) + (0.00000179 x 16.042) + (0.000001 x 83.798) + (0.0000005 x 2.016) + (0.00000009 x 131.293)

Molecular mass of dry air = 28.97 g/mol

Therefore, the molecular mass or weight of dry air is approximately 28.97 g/mol.

Some FAQs about air

What are the main components of air?

Air is a mixture of many gases and tiny dust particles. The main components of dry air are nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%), and other trace gases such as neon, helium, krypton, hydrogen, and xenon¹². Air also contains variable amounts of water vapor, which can range from 0% to 4%¹².

How does air pressure change with altitude?

Air pressure is the force exerted by the weight of air on a unit area of surface. Air pressure decreases with increasing altitude because there are fewer air molecules above a given point as the height increases¹². For example, at sea level, the average air pressure is about 101.325 kPa (14.7 psi), but at 10 km (6.2 mi) above sea level, the average air pressure is only about 26.5 kPa (3.8 psi).

How does air temperature change with altitude?

Air temperature is a measure of how hot or cold the air is. Air temperature changes with altitude depending on the layer of the atmosphere. In the lowest layer, called the troposphere, where most weather occurs, the temperature generally decreases with altitude at an average rate of 6.5 °C per km (3.6 °F per mi)¹². However, in some layers above the troposphere, such as the stratosphere and the thermosphere, the temperature increases with altitude due to various factors such as solar radiation and chemical reactions¹².

How does air humidity affect human comfort?

Air humidity is a measure of how much water vapor is in the air compared to how much it can hold at a given temperature. Air humidity affects human comfort because it influences how well our bodies can cool themselves by sweating¹². When the air is humid, sweat evaporates more slowly from our skin, making us feel hotter and more uncomfortable than when the air is dry¹². Humidity also affects how we perceive the temperature; for example, a hot and humid day feels warmer than a hot and dry day because humid air reduces the cooling effect of evaporation from our skin¹².

Some fun facts about air

• The word “air” comes from the Latin word “aer”, which was derived from the Greek word “aer”, meaning “breath” or “wind”.
• The highest recorded surface wind speed on Earth was 408 km/h (253 mph), measured during Tropical Cyclone Olivia at Barrow Island, Australia, on April 10, 1996.
• The lowest recorded surface air pressure on Earth was 870 hPa (25.69 inHg), measured during Typhoon Tip at Guam in the western Pacific Ocean on October 12, 1979.
• The highest recorded surface air temperature on Earth was 56.7 °C (134 °F), measured at Furnace Creek Ranch in Death Valley, California, USA, on July 10, 1913.
• The lowest recorded surface air temperature on Earth was -89.2 °C (-128.6 °F), measured at Vostok Station in Antarctica on July 21, 1983.

Source:
(1) Air – National Geographic Society. https://www.nationalgeographic.org/encyclopedia/air/.
(2) Air – Simple English Wikipedia, the free encyclopedia. https://simple.wikipedia.org/wiki/Air.
(3) What’s in the Air? | Center for Science Education. https://scied.ucar.edu/learning-zone/air-quality/whats-in-the-air.
(5) Density of air – Wikipedia. https://en.wikipedia.org/wiki/Density_of_air.
(6) Air Density Calculator | What is Air’s Density?. https://www.omnicalculator.com/physics/air-density.