Some Thoughts on Heat

We just started thinking about heat energy (Q) again so I thought I would share a shot from our diagram on the board and a few thoughts. When you add energy to something (any kind of energy) that something changes. If I add a Big Mac to you, you gain weight. If I add kinetic energy to you, you start moving faster. If I add heat to you, you get hotter.... sometimes. We really get two choices every time we add heat to something: 1) Change Temperature or 2) Change State. Take a look at the diagram below.

When we add heat to ice, it wants to get hotter. However, it gets to a point (Melting Point) where it can't get any hotter as a solid, at that point it begins to convert to a liquid, which also takes energy (Heat of Fusion). Once all of the solid has converter we can get hotter again, until we hit another boundary (Boiling Point). No we must use energy to convert to a gas (Heat of Vaporization). At that point we can keep going up (and eventually become plasma.

Although turning ice into steam can be energy intensive and seems tough, its a problem made up of lots of simple steps. Take the example in the graph above, converting 1 kg of ice at -30oC to steam at 120oC. Although it takes 5 different stages of adding energy, each step is pretty simple.

This is kind of unrelated, but I thought you'd enjoy. Here is a video of some experiments with dry ice and a microwave: