How do we define energy?

Question

Which unit represents the larger amount of energy?

What happens to the molecules in a sample of ice as the sample is slowly heated until it liquefies and then vaporizes?

When steam is at 150 C. What happens to the molecules in the sample as the sample is slowly cooled until it liquefies and then solidifies?

Answer 1

We do not really fully understand energy.  I cannot help you with your homework, but I can tell you that we only understand SOME properties of energy.

Answer 2

Energy can simply be defined as ability of a system to do work. However Heat is an exceptional form which is also designated as degraded form of energy.

In SI system its unit of measurement is Joule.

When you provide heat to molecules, their kinetic energy increases resulting in acceleration of their motion and consequently temperature and the process continues till molecules turn into its gaseous forms at higher kinetic energy.

However cooling is the revers of above process. Kinetic energy reduces and intermolecular forces become stronger to bind the molecules with eash other.