Question

what happens to the particles when heat is added to a substance? the particles slow down. the particles speed up. the particles disappear.

Explanation:

When heat is added to a substance, according to the kinetic theory of matter, the energy is transferred to the particles. This added energy causes the particles to move more vigorously. The options "The particles slow down" is incorrect as adding heat does not reduce their motion. "The particles disappear" is also wrong as particles do not vanish when heat is added. The correct behavior is that the particles gain energy and speed up.

Answer:

The particles speed up.