Temperature is used to measure the movement of particles such as atoms and molecules. as temperature increases, what is always true of the particles in a substance? the rate of movement increases. the distance between them decreases. the attraction between them increases. the rate of reaction decreases.

The rate of movement increases.

Explanation:

When temperature increases the kinetic energy of the particles in matter also increases. Particles in matter are always in motion. Temperature increases the velocity or the rate of motion of the particles. Temperature is proportional to the average kinetic energy of the particles. When temperature increases, heat increases which then increases the kinetic energy of the particles in motion. The mathematical expression relation temperature to kinetic energy is as follows:

Avg. K.E. = 3/2 RT

where K.E., R and T are average kinetic energy, universal gas constant and absolute temperature in Kelvin.  

a is the correct answer