Question

how are molecules affected when heat is added? they vibrate slower. they start vibrating faster and then stop. there is no change. they vibrate faster.

Explanation:

When heat is added to a substance, the thermal energy increases the kinetic energy of its molecules. Higher kinetic energy means molecules move (vibrate, in the case of solids) faster. The first option is incorrect as heat increases motion, not slows it. The second is wrong because molecules don’t stop vibrating when heat is added (unless reaching absolute zero, which isn’t the case here). The third is incorrect as heat does affect molecular motion. So the correct answer is that molecules vibrate faster.

Answer:

D. They vibrate faster.