Is Air a Compound or Mixture? (And Why?)

Air is a mixture. It is composed of various gases such as nitrogen, oxygen, carbon dioxide, and trace amounts of other gases, all of which are physically combined but not chemically bonded together. ¹

Well, this was just a simple answer. But there are few more things to know about this topic which will make your concept super clear.

So let’s dive right into it.

Why is air a mixture?

Air is a mixture because it is composed of several different gases, such as nitrogen, oxygen, carbon dioxide, and trace amounts of other gases. These gases are not chemically combined, but rather exist together in the atmosphere, creating a mixture.

Air is a mixture of gases rather than a pure substance because it contains various components in different proportions.

The primary gases in air are nitrogen (approximately 78%) and oxygen (approximately 21%), with the remaining percentage consisting of carbon dioxide, water vapor, argon, and other gases. ^{2 3}

These gases exist in the atmosphere independently of one another and do not undergo chemical reactions to form new compounds. They retain their individual properties and can be separated by physical means, such as fractional distillation or filtration.

In conclusion, air is a mixture because it consists of different gases, including nitrogen, oxygen, carbon dioxide, and others, which coexist in the atmosphere without undergoing chemical bonding.

This mixture of gases in the air is crucial for supporting life on Earth and plays a significant role in various natural processes and human activities.

What type of mixture is air?

Air is classified as a homogeneous mixture. This is because the gases that make up air are uniformly distributed throughout the atmosphere.

In the case of air, the different gases, such as nitrogen, oxygen, carbon dioxide, and others, are thoroughly mixed together and form a single-phase gas.

This means that regardless of where you sample the air, the proportions of the gases will remain relatively constant. 

The gases in air do not separate into distinct layers or settle out due to gravity, as seen in heterogeneous mixtures. Instead, they form a uniform and well-mixed blend that we commonly experience as the Earth’s atmosphere.

Why is air not a compound?

Air is not a compound because it does not consist of chemically bonded elements. A compound is a substance formed when two or more elements chemically combine in specific proportions, creating a new substance with different properties from its constituent elements. ⁴

In contrast, air is a mixture of different gases, primarily nitrogen, oxygen, and traces of other gases. These gases retain their individual identities and properties in the mixture.

They do not undergo chemical reactions or combine in fixed proportions to form a new substance.

Each gas in the air maintains its unique characteristics, such as boiling point, density, and reactivity. As a result, air is considered a mixture rather than a compound.

Further reading

Why is Water a Compound?
Is Water an Element?
Is Air an Element?
Why is Air a Homogeneous Mixture?
Is Water a Homogeneous Mixture?

1. for Science Education, U. C. (n.d.). What’s in the Air? | Center for Science Education. What’s in the Air? | Center for Science Education. https://scied.ucar.edu/learning-zone/air-quality/whats-in-the-air
2. Atmosphere. (n.d.). Atmosphere. https://education.nationalgeographic.org/resource/atmosphere
3. ATMO336 – Fall 2016. (n.d.). ATMO336 – Fall 2016. http://www.atmo.arizona.edu/students/courselinks/fall16/atmo336/lectures/sec1/composition_fall16.html
4. NCI Dictionary of Cancer Terms. (n.d.). National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms