# Average energy in kinetic stores is related to temperature

• The particles in a gas are constantly moving with random directions and speeds. If you increase the temperature of a gas, you transfer energy into the kinetic energy stores of its particles

• The temperature of a gas is related to the average energy in the kinetic energy stores of the particles in the gas. The higher the temperature, the higher the average energy

• So as you increase the temperature of a gas, the average speed of its particles increases. This is because the energy in the particles’ kinetic energy stores is 1/2mv2

# Colliding gas particles create pressure

• As gas particles move about at high speeds, they bang into each other and whatever else happens to get in the way. When they collide with something, they exert a force on it. In a sealed container, the outward gas pressure is the total force exerted by all of the particles in the gas on a unit area of the container walls

• Faster particles and more frequent collisions both lead to an increase in net force, and so gas pressure. Increasing temperature will increase the speed, and also the pressure

• Alternatively, if temperature is constant, increasing the volume of a gas means the particles get more spread out and hit the walls of the container less often. The gas pressure decreases

• Pressure and volume are inversely proportional-when volume goes up, pressure goes down. For a gas of fixed mass at a constant temperature, the relationship is:

• pV=constant, p=pressure, v=volume

# A change in pressure can cause a change in volume

• The pressure of a gas causes a net outwards force at right angles to the surface of its container

• There is also a force on the outside of the container due to the pressure of the gas around it

• Ifa container can easily change its size, then any change in these pressures will cause the container to compress or expand, due to the overall force

# Doing work on a gas can increase its temperature

• If you transfer energy by applying a force, then you do work. Doing work on a gas increases its internal energy, which can increase its temperature

• You can do work on a gas mechanically. The gas applies pressure to the plunger of the pump, and so exerts a force on it. Work has to be done against this force to push down the plunger

• This transfers energy to the kinetic energy stores of the gas particles, increasing the temperature. If the pump is connected to a tyre, you should feel it getting warmer