Beginner Topic 1044 of 1102 Biochemistry, Environment & Industry

Atmospheric Composition

The atmosphere is mostly nitrogen and oxygen with trace gases.

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In-depth explanation of Atmospheric Composition

Dry air is composed of about 78.08 percent nitrogen, 20.95 percent oxygen, 0.93 percent argon and about 0.04 percent carbon dioxide by volume. Trace gases include neon, helium, methane, krypton and hydrogen, while water vapour varies from near zero up to about 4 percent. The atmosphere is divided into layers by temperature: the troposphere, the stratosphere containing the ozone layer, the mesosphere and the thermosphere. Most weather occurs in the troposphere. The composition is maintained by biological, geological and chemical cycles.

Going deeper: Atmospheric Composition

Key ideas: Dry air by volume: N2 78.08 percent, O2 20.95, Ar 0.93, CO2 about 0.042 (420 ppm), plus Ne, He, CH4 and others in trace; water vapor varies 0 to 4 percent. Layers: troposphere (to 12 km, weather), stratosphere (ozone, to 50 km), mesosphere, thermosphere. Pressure falls roughly by half every 5.5 km.

Common mistakes and connections: Students believe oxygen is the main gas, or that temperature always falls with height; it rises in the stratosphere because ozone absorbs UV. Composition is nearly constant up to about 80 km. Links to gas laws, partial pressures (Dalton) and ozone.

Visualization of Atmospheric Composition

Composition of dry air by volume. Nitrogen and oxygen make up about 99 percent, with argon and a trace of carbon dioxide and others. The interactive lesson shows this as a live animation or chart.

Worked example and use case

At sea level the total pressure of the atmosphere is about 101.3 kPa.

Frequently asked questions about Atmospheric Composition

What is Atmospheric Composition?

The atmosphere is mostly nitrogen and oxygen with trace gases.

Is Atmospheric Composition a beginner, intermediate or advanced topic?

Atmospheric Composition is a beginner topic in Biochemistry, Environment & Industry. It needs no earlier chemistry lessons and is a good starting point.

What should I learn before Atmospheric Composition?

Study these earlier topics in Biochemistry, Environment & Industry first: Composite Materials, Smart Materials, Biomaterials.

What comes after Atmospheric Composition?

The next topics in Biochemistry, Environment & Industry are Greenhouse Effect and Global Warming.

Can I practise Atmospheric Composition with quizzes?

Yes. The interactive lesson includes a self-check question on Atmospheric Composition, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.

Where Atmospheric Composition fits in Biochemistry, Environment & Industry

Atmospheric Composition is topic 69 of 127 in Biochemistry, Environment & Industry.