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Key Idea 3
Concept Question: How do scientists describe energy transfers as heat?

To cool the food within a refrigerator, the refrigerant fluid removes heat from the inside of the refrigerator while releasing heat to the air outside the refrigerator. But what exactly is heat? How do scientists describe it?


What do we know?

Heat is a transfer of energy. This is important to understand. An object cannot possess heat; rather, energy is absorbed or released as heat. Heat is energy in transit.
 A glass of lemonade

Heat will spontaneously flow from a region of high temperature to a region of low temperature until the two regions are at the same temperature. This is an intuitive concept; you know that a cold glass of lemonade will eventually reach room temperature. This happens because the lemonade absorbs heat from the surrounding air, so that the temperature of the lemonade increases. The temperature of the air in the room will actually decrease as well, but only by a tiny amount, because there is so much air surrounding the lemonade.