As the average speed of particles in a sample of matter decreases, two factors that also decrease are:
Temperature: Temperature is a measure of the average kinetic energy of particles in a substance. When the average speed of particles decreases, it indicates a reduction in their kinetic energy, which leads to a lower temperature.
Pressure: In gases, the pressure is related to the kinetic energy of gas particles and their speed. When the average speed of gas particles decreases, they collide with the walls of their container less frequently and with less force, resulting in a decrease in pressure.
So, both temperature and pressure tend to decrease as the average speed of particles in a sample of matter decreases.