How are the molecules in a hot cup of water different from the molecules in a cold cup of water?

Answer 1

All molecules move, unless as 0 kelvin (which has never been reached). As temperature increases, the molecules move more and more. This is why ice melts and water evaporates. It takes energy to change phases so a hot cup of water will have an easier time evaporating since it already has more kinetic energy. As for the molecules in both cups, they are both in the liquid phase so they will have the same types of motion.

If the two cups have the same volume and substance in it, then it is understood that the hotter of the two will evaporate faster.

Answer 2

In a hot cup of water, molecules move more energetically to overcome the intermolecular forces among them to enter gas phase, and it evaporates more quickly than the molecules in a cold cup of water, because most water molecules in a cold cup don't have enough energy to break free to enter gas phase, so it evaporates slower.