According to the ideal gas law, the pressure of a gas is directly proportional to its temperature when the volume is constant. This relationship is expressed by the equation:
P1/T1 = P2/T2
where P1 and T1 are the initial pressure and temperature, and P2 and T2 are the final pressure and temperature.
If the temperature increases while the volume remains constant, according to the equation above, the pressure of the gas will also increase. This is because an increase in temperature causes the gas molecules to move faster and collide with the container walls more frequently and with greater force, resulting in an increase in pressure.
On the other hand, if the volume decreases while the temperature remains constant, the pressure of the gas will increase. This is known as Boyle's Law, which states that the pressure and volume of a gas are inversely proportional when the temperature is constant.
Therefore, if the temperature increases and the volume decreases, the pressure of the gas will increase due to both the direct effect of temperature and the indirect effect of volume.