This is the second in a series of Heat Pump 101 videos from instructor and author, John Siegenthaler, P.E.. “The Difference Between Energy & Power” was the previous lesson in the series. You can enroll in John’s Heat Pump 101 course for free to learn the very basics of heat pumps in less than an hour.

Here’s the key idea from this video:

All materials that have a temperature above absolute zero. There’s nothing on the earth that is at absolute zero. Everything is above that. Liquid nitrogen gets close to that temperature, but it is still not at absolute zero.

Here’s an example to consider:

Imagine your hand touching a piece of metal that’s at five degrees. You would sense that that piece of metal is very cold and yet, if that metal were cool to zero degrees Fahrenheit, it would contain less heat. We would have to remove heat from a five degree Fahrenheit piece of metal to get its temperature down to zero degrees Fahrenheit, and just the fact that we removed heat to change its temperature implies that there was heat there to begin with.

Even though it feels cold, if there’s a material at a lower temperature, there is still heat available in that material. Heat naturally moves from any material at some given temperature to a material at a lower temperature.

The next video in this series is covers the three modes of heat transfer, which we’ll cover in the next post. If you want to see that video now or jump ahead to the others, you can find them all in John Siegenthaler’s free Heat Pump 101 course.