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Q & A: temperature and heat

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Most recent answer: 10/22/2007
Can you explain the difference between temperature and heat?
- Aimee (age 13)
Great Lakes College, Australia

Yes, temperature is a measure of how much random jiggling there is of the little parts of things, such as atoms and molecules. In other words, it's a measure of how much energy a typical little part has in the form of those random motions. Of course there's a far more precise and general definition, but at least that should be ok for starters.

Heat is a measure of how much energy flows from one object to another because of their different temperatures. No matter what the objects are made of or what their sizes are, heat will flow from the hotter (higher temperature) one to the cooler one, unless work is done (as in a refrigerator).

Notice that for big objects, the total amount of thermal energy flowing around is bigger than for small objects. On the other hand, the temperature of a little piece of a uniform object is the same as the temperature of the whole thing.

Sometimes people use "heat" to mean the total amount of random (thermal) energy in some object. However, that definition is not the standard one and can lead to confusion in some cases.

Mike W.

(published on 10/22/2007)

Follow-Up #1: temperature and thermal energy

Could you explain the difference between temperature and thermal energy?
- Rachelle (age 12)
Yes. There's a certain amount of energy that an object would have even at zero absolute temperature. When the object heats up, there's additional energy rattling around randomly among all the little parts- atoms, molecules, etc. That extra energy is what we call the thermal energy.
The temperature is, approximately a measure of how much of that thermal energy there is per little part. So two cups of boiling water have twice as much thermal energy as one cup, even though they both have the same temperature.
At a very deep, general level, the temperature is a measure of how much thermal energy has to be added to a system to double the number of different quantum states available to it.

Mike W.

(published on 10/22/2007)

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