(POM) Behavior of Gases Lesson

Behavior of Gases

How do hot air balloons work? Air is a mixture of many gases, primarily nitrogen and oxygen. When any gas is heated, its molecules gain kinetic energy and push harder against the inside walls of their container. In other words, the molecules speed up and begin to move faster causing them to push against the walls of their container at a more rapid rate. The density of the gas also decreases because of the spreading out of the gas molecules. The hot air balloon expands and the heated air causes it to rise since the hot air is less dense than the cooler air outside the balloon. While in flight, the balloon operator keeps the air in the balloon hot by occasionally blasting the air with a large burner. In this lesson, you will learn all about the properties of gases and the mathematical relationships between the pressure, volume, temperature, and amount of a gas.

Compressibility is a measure of how much a given volume of matter decreases when placed under pressure. Gases are compressible because most of the volume of a gas is composed of large amounts of empty space between the gas particles. When a gas is compressed, the gas particles are forced closer together.

Factors that Affect Pressure:

• Amount of Gas

The pressure inside a container is dependent on the amount of gas inside the container. Look at the picture below. When gas is pumped into a closed rigid container, the pressure increases. If the number of gas particles is doubled, the pressure doubles.

• Volume of Container

If the volume of a container is decreased, the gas molecules have less space in which to move around. As a result, they will strike the walls of the container more often, resulting in an increase in pressure. Look at the picture below. When the volume of an enclosed container of gas is reduced, the gas pressure increases. In other words, if the volume is cut in half then the pressure doubles.

• Temperature

An increase in the temperature of an enclosed gas causes the pressure to increase. This is because the added kinetic energy causes the air molecules to move faster, so they impact the container walls more frequently and with more force. Look at the picture below. If the temperature is doubled, then the pressure doubles.

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