Properties of Gases Compressibility A gas can expand

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.