Whether you are consciously aware of it or not, you pay attention to the temperature constantly.  Are you too hot or too cold?  If you touch something that’s too hot, like inadvertently touching a pan that has been heated up on the stove, you pull your hand back quickly, reacting to the temperature of the pan.  Afterwards, you might go grab a piece of ice and hold it on your hand, knowing that having the cold ice in contact with where you burned your skin will feel good.  So, though you think about temperature every day, you probably don’t have a very good definition for what the temperature means.  You know how to measure it with a thermometer, but you may not necessarily know what that measurement is describing.

Heat is another word that we use every day, but if someone asked you to explain what heat is, you might have trouble coming up with a good definition.  In fact, the way most of us use the word heat in every day conversation is actually at odds with the way heat is defined scientifically.  As a result, the first thing we need to do in beginning thermodynamics is understand the differences between heat, temperature, and energy.