Question

the hot metal objects in the photo cool quickly and soon stop glowing what happens to the energy as the metal parts cool

Answer 1

Answer:

What happens when a piece of hot metal is dropped in room temperature water. Over time the metal will cool and the water will heat up. Eventually the two objects will have the same temperature. They are then said to be in thermal equilibrium with one another.

During the intervening time the hot metal is transfering energy to the water. How can we tell?

The water can do more work than it could before. The water might boil, for example. A piston could be placed over the water in a sealed container, and the piston would lift, much like the lid rattling on a pot of boiling water. The piston would gain gravitation potential energy in lifting, so the heated water did work on it. The original energy came from the hot piece of metal.