Question

what happens to the average kinetic energy of particles when the temperature decreases? a the particles move slower. b the particles stop moving. c the particles move faster. d the particles stay the same.

Explanation:

The average kinetic energy of particles is related to temperature. Temperature is a measure of the average kinetic energy of the particles. When temperature decreases, the average kinetic energy of the particles decreases. Lower kinetic energy means the particles move slower (since kinetic energy is related to the speed of the particles: $KE = \frac{1}{2}mv^2$, where $KE$ is kinetic energy, $m$ is mass, and $v$ is velocity). Particles never stop moving completely (only at absolute zero, which is a theoretical concept and not achievable in normal conditions), so option B is wrong. A decrease in temperature leads to slower, not faster (option C) or unchanged (option D) particle motion.

Answer:

A. The particles move slower.