Properties of Gases

Compressibility A gas can expand to fill its container, unlike a solid or liquid. Gases are easily compressed, or squeezed into a smaller volume.

Compressibility Compressibility is a measure of how much the volume of matter decreases under pressure. You can use kinetic theory to explain why gases can be compressed more easily than liquids or solids can.

Compressibility Gases are easily compressed because of the space between the particles in a gas. Remember that the volume of the particles in a gas is small compared to the overall volume of the gas.

Compressibility The distances between particles in a gas are much greater than the distances between particles in a liquid or solid. Under pressure, the particles in a gas can be forced closer together, or compressed.

Compressibility At room temperature, the distance between particles in an enclosed gas is about 10 times the diameter of a particle.

Factors Affecting Gas Pressure The motion of the particles is constant and random. Because there are no significant forces of attraction or repulsion among particles in a gas, particles in a gas can move freely.

Factors Affecting Gas Pressure Four variables are generally used to describe a gas: Pressure (P) in kilopascals Volume (V) in liters Temperature (T) in kelvins Moles (n)

Factors Affecting Gas Pressure The amount of gas, volume, and temperature are factors that affect gas pressure. By adding gas to a container you are increasing the number of particles. Increasing the number of particles increases the number of collisions, which explains why the gas pressure increases.

Factors Affecting Gas Pressure If a gas is added to an enclosed, ridged container it will increase the pressure. Once the pressure exceeds the strength of the container, it will burst.

Factors Affecting Gas Pressure If the pressure of the gas in a sealed container is lower than the outside air pressure, air will rush into the container when it is opened. If the pressure of a gas in a sealed container is higher than the outside air pressure, the gas will flow out of the container. EX: aerosol cans

Factors Affecting Gas Pressure You can raise the pressure exerted by a contained gas by reducing its volume. The more the gas is compressed, the greater the pressure that the gas exerts inside the container. EX: piston

Factors Affecting Gas Pressure As a gas is heated, the temperature increases and the average kinetic energy of the particles in the gas increases. If you double the temperature, you double the pressure.