* In the case of pressure,
The pressure is described as in terms of force per per unit area.
If the pressure is applied to the gas, the gas is collected in certain region and acquire some energy due to the force acting on it. Thus, the pressure increase the energy of the gas.
* In the case of volume,
When the volume of the gas is increased, the expansion of the gas takes place or we can say the gas uses its energy to do the work for expansion.
* In the case of temperature,
The molecules present in the gas acquire the thermal energy in the presence of high temperature. This energy corresponds to the zig zag motion of the molecules in the gas.