Answer:
See explanation.
Step-by-step explanation:
Are you literally posting your entire you chemistry homework on this site, one question at a time? Anyways, the heat death refers to the second law of thermodynamics and entropy. Heat is constantly flowing from warmer to cooler objects and never the other way around. This heat flow increases entropy, which is constantly increasing. The universe will eventually disperse all of its heat energy away to continuously increase entropy and reach a limit as the temperature reaches 0 K at which point all molecular motion will cease and so will the life of the universe.