Air is probably one of the most underrated matter in our lives. Even we often take it for granted. Just because we don’t actually ‘see’ it, doesn’t mean it’s not there.

Of course it’s there. And it matters a lot in our daily life (I mean, we need air to breathe in right?).

Now if you have realized that air is a matter, you probably are wondering to which category does it belong?

Is air an element, compound, or mixture?

Air is a mixture. Air consists of various types of atoms AND it can be physically separated.

Wait, what?

Air can be separated PHYSICALLY?

Yes, you read that correctly. To know more about it, be sure to read along till the end of this post!

What Does Air Consist Of?

Air is a matter that consists of various elements and compounds such as Nitrogen (about 78%), Oxygen (about 21%), Argon (1%), and little amount of other matter such as Carbon dioxide and water vapor (H2O).

Different types of gas combine together and they appear as the air that we enjoy every day in our life.

Is Air A Mixture?

Yes, air is a mixture. It consists of different atoms and it can be separated PHYSICALLY. This makes air eligible to be considered a mixture.

In chemistry, mixture is a matter that consists of 2 or more types of atoms that is able to be broken down PHYSICALLY.

Air consists of various elements and compounds including nitrogen, oxygen, argon, carbon dioxide, hydrogen, water vapor, and many other.

All of these things combined together to form AIR. When they are combined, they can be separated through a physical process.

Why is air NOT a compound?

Air is NOT a compound because, although it consists of various atoms, you can break it down through a physical process (not a chemical process).

To be called a compound, a matter must consist of two or more elements AND it must not be able to be separated physically. You need a chemical process to separate a compound.

Air is not a compound because it doesn’t satisfy the requirement.

Yes, air does consists of various elements, i.e. Nitrogen, Oxygen, and other gases such as Carbon dioxide and Hydrogen.

BUT, here’s the thing: AIR can be separated physically. Yes, you read that right. You don’t need a chemical process to break down the air of the earth.

To break down an air, you can perform a physical process called FRACTIONAL DISTILLATION.

How Do You Separate Air?

This can be done through a physical process called distillation.

Distillation is one of the techniques to separate a matter. Distillation takes the benefit of the different boiling points or evaporation rates of the mixture’s components. In distillation, a mixture is heated to let its components condensed.

And yes, it’s a PHYSICAL process, not a chemical process.

Each element and compound has different boiling points. For example, oxygen has a boiling point of -183 degree Celcius while Chlorine has a boiling point of -34.04 degrees Celcius.

If the components of the mixture has a significant difference of boiling points, it can be separated through SIMPLE DISTILLATION.

However, if the components of the mixture have close differences of boiling points, it can be separated through FRACTIONAL DISTILLATION.

Air consists of various gases, and at least 3 of them has close boiling points.

Component of airBoiling point
Nitrogen-195.8 degrees Celcius
Oxygen-183.0 degrees Celcius
Argon-185.8 degrees Celcius
(not all components are listed on the table)

Separation of Air Through Fractional Distillation

Fractional distillation is a common way to separate air or to extract the main component of air (oxygen or nitrogen).

Generally, here are the steps of air separation through fractional distillation.

  1. The air is filtered to remove dust or debris
  2. The air is cooled down (heading to -200 degrees Celcius) so it becomes LIQUID.
  3. The water vapor (H2O) will condense and removed.
  4. When it reaches -79 degrees Celcius, the Carbon Dioxide (CO2) is removed.
  5. The remaining liquid mixture enters a heated column. This column has a colder part at the top and a ‘warmer’ part at the bottom. Since nitrogen and oxygen have different boiling points, they will naturally separate in the column (nitrogen escapes through the upper pipe, and oxygen is pumped out to the lower collection pipe).

P.S. If you want to separate Argon, place another collection pipe in the center of the fractioning column (between oxygen pipe and nitrogen pipe). As shown on the table (earlier in this post), the boiling point of Argon (-185.8 degrees Celcius) is between Nitrogen boiling point (-195.8 degrees Celcius) and the Oxygen boiling point (-183.0 degrees Celcius). This is why the Argon collection pipe should be placed between the other two.

Daniel Smithson

Hi, I'm Daniel Smithson, a Chemistry teacher for over 35-years and the founder of Learning should be fun and accessible to all. Find out more about our mission here:

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