Heat v. Temperature

Out in the “real world” people speak about temperature and heat carelessly and it might seem that temperature and heat are essentially the same thing but, in fact, although they are related, they are very different.

Temperature is a measure of the average kinetic energy of the molecules in something. Although some molecules are moving faster than average and some slower, we can't (and our measuring devices can't) sense those microscopic differences, so an average does what we need it to do. Temperature is what you are discussing when you say something is hot or cold.

Heat is the total kinetic energy that something has. This is the result of adding up all of the energies of all of the atoms. As a result, the amount of heat is dependent on the amount of something that is present as well as the temperature.

A simple way to see the difference is to picture a thimble of boiling water and a bathtub of cold water. The water in the thimble is hotter (the average molecule in the thimble is moving very fast) but the bathtub of water has more heat (even though the molecules are slower, there are so many that the total energy is huge.)

If you feel unsure about that, just imaging dumping the thimble of water into the bathtub...the temperature would barely change. The amount of heat in the thimble is actually very small.

It is also important to understand how these words are misused. Heat is a noun. Heat can be added to something or taken away. Heat transfers. Hot and cold on the other hand are adjectives. Things can be hot or cold, things can become hotter or colder, but there is no such thing as hot and there is no such thing as cold. When your mom tells you to shut the refrigerator door because you are letting the cold out, she really means that you are letting cold AIR out and letting warm AIR in.

To understand heat more, we need to think about the transfer of heat