Air is made up of a complex “recipe” of other elements, which leads to the question:

Is air a compound or a mixture?

Air is a homogeneous combination of several gases; therefore, it is a mixture, not a compound. This mixture of gas is made up of nitrogen, oxygen, argon, water vapor, and tiny amounts of various other gases.

In this article, we will explore the question in more depth, looking at the properties of both compounds and mixtures and how they differ. We will also touch on the different types of mixtures and how air fits into this classification.

Mixture vs. Compound

When we use the words “mixture” and “compound,” what do we mean?

In chemistry, a mixture is a combination of elements (or compounds) that are physically connected but can also be physically separated (as opposed to chemically separated). Many mixtures still have the characteristics of the elements or compounds they contain.

Mixtures are formed whenever two or more substances are physically mixed together. Compounds, on the other hand, are substances made when two or more elements chemically combine.

Compounds and mixtures share some traits in common. For instance, they can be combined in any proportion or ratio of elements. Mixtures and compounds share a number of other physical and chemical properties.

While compounds can’t be chemically separated, their constituent parts can be. Mixtures can be physically separated by various means. These include processes like distillation, evaporation, chromatography, and filtration, all of which are used on different types of mixtures.

Mixtures and compounds are both important because they are essential elemental combinations. Almost nothing in our world is possible without one or the other; often both.

Both play vital roles in the chemical processes that support all life on earth. They are also crucial to many chemical processes in non-living things.

Is Air a Mixture or a Compound?

As previously mentioned, air is a homogeneous mixture of several gases. These gases are distinct and can be physically separated. While separating the components in air is difficult and requires special equipment, it can be done.

Air is composed of:

  • Nitrogen
  • Oxygen
  • Argon
  • Various other gases in tiny amounts
  • Water vapor

While air may vary in the amount of a specific gas present, it always includes a wide variety of compounds. These are constantly present and affect the way air reacts as a cohesive mixture.

What Makes Air a Mixture?

As I mentioned, compounds are the combination of different elements where it is difficult or impossible to separate them. When compounds are created, they also give off energy. This is unlike mixtures, where no energy is generated.

Mixtures are combinations of elements that don’t cause chemical reactions. Additionally, mixtures can be physically separated back into their constituent parts.

Air is a mixture precisely because it can be broken down into its constituent parts. A demonstration of this is how air shows the properties of each of its constituent gases. For example, despite having many other gases in it, air supports combustion because of the presence of oxygen.

Air is a mixture with variable composition.

Air has different component gases in varying amounts at different places. It is made up of differing amounts of oxygen, nitrogen, argon, hydrogen, carbon dioxide, water vapor, and smaller amounts of many other components. All of these things can be physically separated from one another into distinct elements.

Compounds are only able to be separated by a chemical process.

No chemical processes are required to separate the elements in air. Separating the constituent parts of air is done using a physical process called fractional distillation.

What is Distillation?

Distillation is a technique used to separate mixtures of matter. It takes advantage of the fact that different gases have their own boiling points and evaporation rates. Distillation heats these gases until they boil and evaporate. Since each gas is different, this happens at individual moments, and they can be physically separated.

Simple distillation can be used for mixed components with very different boiling points. But since the components in air all boil at temperatures close together, they require fractional distillation. For example, oxygen boils at -183 degrees Celsius, nitrogen at -195.8 degrees Celsius, and argon at -185.8 degrees Celsius.

What Does Air Consist of?

While it’s possible to generalize about the contents of air, the exact makeup can be pretty malleable. This depends on your exact location and environment, as well as potential industrial or weather phenomena.

The air you’re breathing right now is made up of numerous elemental gases. Most of it is nitrogen and oxygen. Other inert gas elements also exist in trace quantities. There are small but growing amounts of carbon dioxide, sulfur oxide, and nitrogen oxide. Hydrogen and neon are also present.

Air also contains aerosols, such as dust and pollen.

This happens naturally as air flows and interacts with the environment. They can also be air pollutants like soot, smoke, car exhaust, and power plant fumes.

Too many of these particles in the air make it difficult for plants and animals to breathe. Over time, they can cause cancers and numerous other diseases.

By burning fossil fuels like coal, oil, and gasoline, cars and power plants create carbon dioxide. This is the most significant contributor to human-caused climate change. But air pollution also has effects on a daily basis.

Air pollution measuring over 100 on the Air Quality Index (AQI) is the equivalent of breathing car exhaust. Forest fires, car traffic, and power plants can all cause high AQI levels. It’s unsafe for people and animals to be outside in these conditions.

Besides aerosols, air also has plenty of microorganisms. These are known as bioaerosols. These microbes circulate through the air and can travel incredible distances. Some can make it unbelievably far on wind and rain.

Learning About Air as a Mixture

To review what we have learned: air is a mixture, meaning it is composed of elements that have a physical connection but are distinct. This means that they can be physically separated and that air retains the characteristics of its components (such as combustibility due to its oxygen content).

Again, air in not a compound.

Understanding how air works as a mixture is vital as a foundational point for many scientific questions. Thanks for reading, and, as always, breathe easy, my friend.

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.

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Medical Disclaimer: The information provided by Respiratory Therapy Zone is for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Please consult with a physician with any questions that you may have regarding a medical condition.