The Chemical Composition of Air
Jul 07, · Nearly all of the Earth's atmosphere is made up of only five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Several other compounds are also present. Although this CRC table does not list water vapor, air can contain as much as 5% water vapor, more commonly ranging from %. The % range places water vapor as the third most common gas (which alters the other . Air is a mixture of about 78% of nitrogen, 21% of oxygen, % of argon, % of carbon dioxide, and very small amounts of other gases.   There is an average of about 1% water vapour. Animals live and need to breathe the oxygen in the air.
The air you breathe is made up of lots of other things besides oxygen! So, what is air made of? Ask zir friends and, odds are, a few will correctly say nitrogen. It accounts for a fifth of the atmosphere. That leaves about one percent of the air unaccounted for. The question is: What is that one percent? Stop and guess! Most would guess carbon dioxide, which actually makes up less than a twentieth of mwde percent, villainous greenhouse notoriety notwithstanding.
Few would choose the element only discovered around a century ago: Argon. Argon was discovered by a Scot, William Ramsay, os eventually won the Nobel prize for his work with gases.
Anyway, that was just a hundred years ago. Ramsay died in How transient is fame—which is maybe why his existence is memorialized by a lunar crater that bears his name. The lunar crater, Ramsay center. So argon continues pf permeate our lungs, while the person responsible for our thoughts about it has vanished with barely a trace.
I thought for a moment there was going to be profundity in all this somewhere, but I guess How to make template for powerpoint was wrong. From the beautiful stars and planets to magical auroras and eclipses, he covers everything under the Sun and Moon!
But this is a "nice" article. We won't go into ir theory's", such as the "chemtrail sprayings", oops, I meant what's in lt "contrails" Skip to main content. You are here This Week's Amazing Sky. What Is Air Made Of? By The Editors. January 29, About This Blog. Related Articles Astronomy Moon. Tags gases. What do you want to read next? Take what is a state trooper Breath!
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Jan 29, · It doesn’t hurt you and it doesn’t help you, which is sort of like the government of Monaco. 2. Air’s second most common component is oxygen, which is on everyone’s “favorite element” list. It accounts for a fifth of the atmosphere. 3. That leaves about one percent of the air unaccounted for. Air, mixture of gases comprising the Earth’s atmosphere. The mixture contains a group of gases of nearly constant concentrations and a group with concentrations that are variable in both space and time. The atmospheric gases of steady concentration (and their proportions in percentage by volume). Air is made of ~80% nitrogen (N_2 - confusingly, two atoms of nitrogen stuck together are also called nitrogen) most of the rest oxygen (O_2) and a handful of other gasses. As Matt Westwood says, oxygen is produced by plant photosynthesis.
The atmosphere of Earth is the layer of gases , commonly known as air , retained by Earth's gravity , surrounding the planet Earth and forming its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface , absorbing ultraviolet solar radiation , warming the surface through heat retention greenhouse effect , and reducing temperature extremes between day and night the diurnal temperature variation.
By volume, dry air contains Air composition, temperature, and atmospheric pressure vary with altitude, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres.
Earth's atmosphere has changed much since its formation as primarily a hydrogen atmosphere, and has changed dramatically on several occasions—for example, the Great Oxidation Event 2. Humans have also contributed to significant changes in atmospheric composition through air pollution, especially since industrialisation , leading to rapid environmental change such as ozone depletion and global warming.
The atmosphere has a mass of about 5. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around km 75 mi.
Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earth's atmosphere and its processes is called atmospheric science aerology , and includes multiple subfields, such as climatology and atmospheric physics.
The three major constituents of Earth's atmosphere are nitrogen , oxygen , and argon. Water vapor accounts for roughly 0. Besides argon, already mentioned, other noble gases , neon, helium, krypton, and xenon are also present. Filtered air includes trace amounts of many other chemical compounds.
Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores , sea spray , and volcanic ash. Various industrial pollutants also may be present as gases or aerosols, such as chlorine elemental or in compounds , fluorine compounds and elemental mercury vapor.
Sulfur compounds such as hydrogen sulfide and sulfur dioxide SO 2 may be derived from natural sources or from industrial air pollution. A volume fraction is equal to mole fraction for ideal gas only, also see volume thermodynamics B ppmv: parts per million by volume C The concentration of CO 2 has been increasing in recent decades D Water vapor is about 0. The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction, is about This is decreased when the air is humid.
The relative concentration of gases remains constant until about 10, m 33, ft. In general, air pressure and density decrease with altitude in the atmosphere. However, the temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions see the temperature section, below.
In this way, Earth's atmosphere can be divided called atmospheric stratification into five main layers. Excluding the exosphere, the atmosphere has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. The exosphere is the outermost layer of Earth's atmosphere i. It extends from the exobase , which is located at the top of the thermosphere at an altitude of about km above sea level, to about 10, km 6, mi; 33,, ft where it merges into the solar wind.
This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase.
The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind.
The exosphere is located too far above Earth for any meteorological phenomena to be possible. However, the aurora borealis and aurora australis sometimes occur in the lower part of the exosphere, where they overlap into the thermosphere.
The exosphere contains many of the satellites orbiting Earth. The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause which separates it from the mesosphere at an altitude of about 80 km 50 mi; , ft up to the thermopause at an altitude range of — km — mi; 1,,—3,, ft.
The height of the thermopause varies considerably due to changes in solar activity. The lower part of the thermosphere, from 80 to kilometres 50 to mi above Earth's surface, contains the ionosphere. The air is so rarefied that an individual molecule of oxygen , for example travels an average of 1 kilometre 0.
This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between. It is this layer where many of the satellites orbiting the earth are present. The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere.
It extends from the stratopause at an altitude of about 50 km 31 mi; , ft to the mesopause at 80—85 km 50—53 mi; ,—, ft above sea level. Temperatures drop with increasing altitude to the mesopause that marks the top of this middle layer of the atmosphere. Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can be sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise.
They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events TLEs occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance.
It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft.
The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km 7. It contains the ozone layer , which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines a layer in which temperatures rise with increasing altitude.
This rise in temperature is caused by the absorption of ultraviolet radiation UV radiation from the Sun by the ozone layer, which restricts turbulence and mixing. The stratospheric temperature profile creates very stable atmospheric conditions, so the stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest.
The stratosphere is the highest layer that can be accessed by jet-powered aircraft. The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km 7. The troposphere is bounded above by the tropopause , a boundary marked in most places by a temperature inversion i. Although variations do occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface.
Thus, the lowest part of the troposphere i. Earth's surface is typically the warmest section of the troposphere. Fifty percent of the total mass of the atmosphere is located in the lower 5. Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus types generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate the tropopause from below and rise into the lower part of the stratosphere.
Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft. Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties:.
The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as pascals This is sometimes referred to as a unit of standard atmospheres atm. Total atmospheric mass is 5. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather. If the entire mass of the atmosphere had a uniform density equal to sea level density about 1.
It actually decreases exponentially with altitude, dropping by half every 5. However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account. In summary, the mass of Earth's atmosphere is distributed approximately as follows: . By comparison, the summit of Mt. Everest is at 8, m 29, ft ; commercial airliners typically cruise between 10 and 13 km 33, and 43, ft where the thinner air improves fuel economy; weather balloons reach Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply.
The various layers of Earth's ionosphere , important to HF radio propagation, begin below km and extend beyond km. By comparison, the International Space Station and Space Shuttle typically orbit at — km, within the F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months, otherwise, orbital decay will occur resulting in a return to earth.
Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as — km. The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where the temperature stabilizes through a large vertical distance through the rest of the troposphere. In the stratosphere , starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by the capture of significant ultraviolet radiation from the Sun by the dioxygen and ozone gas in this region.
Still another region of increasing temperature with altitude occurs at very high altitudes, in the aptly-named thermosphere above 90 km. Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on the gas pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile see illustration to the right , and does not mirror altitudinal changes in density or pressure.
The density of air at sea level is about 1. Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air a form of the ideal gas law. Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula.
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