Question

What happens to the particles of a solid when heat is added? (speed up or slow down)

Answer 1

When heat is added to a solid, the particles in the solid gain energy and begin to vibrate more rapidly. This increase in energy causes the particles to speed up, moving more vigorously within their fixed positions in the solid structure. If enough heat is added, the solid may eventually reach its melting point and transition into a liquid state, where the particles move more freely. So, to answer your question, the particles of a solid speed up when heat is added.