Is Air Made of Matter?

Woman and child flying a red kite

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Is air made of matter? You can't see or smell the air, so you may be wondering whether or not it is made of matter. Here is the answer, plus how you can prove air (or any other phenomenon) consists of matter.

Well, Is It?

Yes, air is matter. Anything and everything you can touch, taste or smell consists of matter. The matter has mass and takes up space. You can prove that air is matter a couple of ways.

How Can You Tell Air Is Matter?

One way is to blow up a balloon with air. Before you added the balloon, it was empty. When you added air, the balloon expanded, so you know it is filled with something! A balloon filled with air sinks to the ground. The compressed air is heavier than its surroundings, so the air has mass or weight.

The matter in the air is what supports the enormous weight of a plane. It also holds clouds aloft. The average cloud weighs about a million pounds. If there were nothing between a cloud and the ground, it would fall.

Also, consider the ways you experience air. You can feel the wind and see that it exerts a force on the leaves on trees or a kite. Pressure is mass per unit volume, so if there is pressure, you know the air must have mass.

If you have access to the equipment, you can weigh air on a scale. You either need a large volume or else a sensitive scale. Weigh a container filled with air. Use a vacuum pump to remove the air. Weigh the container again. This proves something that had mass was removed from the container. Also, you know the air you removed was taking up space. Therefore, it fits the definition of matter.

What Type of Matter Is Air?

Air is an example of a gas. Other common forms of matter are solids and liquids. A gas is a form of matter that can change its shape and volume. If you consider air in a balloon, you can squeeze the balloon to change its shape. You can compress a balloon to force the air into a smaller volume. When you pop the balloon, the air expands to fill a larger volume.

If you analyze air, it consists mostly of nitrogen and oxygen, with smaller amounts of several other gases, including argon, carbon dioxide, and neon. Water vapor is another important component of air.

The Amount of Matter Isn't Constant

The amount of matter in a sample of air isn't constant from one place to another. The density of air depends on temperature and altitude. If you took a liter of air from sea level, it could contain many more gas particles than a liter of air from a mountaintop, which in turn would contain much more matter than a liter of air from the stratosphere. Air is most dense close to the surface of the Earth. At sea level, there is a large column of air pushing down on the surface, compressing the gas at the bottom and giving it a higher density and pressure. It's like diving into a pool and feeling the pressure increase as you go deeper into the water, except liquid water doesn't compress nearly as readily as gaseous air.

Seeing and Tasting Air

While you can't see or taste the air, this is because it's a gas. The particles in the air are very far apart. If air is condensed into its liquid form, it becomes visible. It still doesn't have a flavor (not that you could taste liquid air without getting frostbite). Using human senses isn't a definitive test for whether something is matter or not. For example, you can see light, yet it's energy and not matter!