Pressure can be increased by:
Boyle concluded that volume could only be inversely proportional to pressure for a fixed mass of gas and at a constant temperature if gases contained particles that were moving around. This and subsequent discoveries triggered the Industrial Revolution in the 18th century.
Forces applied to the particles in a gas result in a transfer of energy.
Work done = force × distance
Since the volume of the gas has decreased, the pressure increases because the particles are moving in less space and collide more often. The temperature of the gas is not fixed in most applications and the increased pressure leads to an increase in temperature. This is because the temperature is a measure of the average kinetic energy of particles – the increase in the internal energy of the gas (as kinetic energy of the particles) means that the temperature must increase.
This process explains why a bicycle pump gets warm when it is used to inflate a tyre.