Temperature and heat
Temperature measures how hot or cold something is; heat is energy that flows between objects because they are at different temperatures.
Practise this conceptTemperature and heat get used interchangeably in everyday speech, but they describe genuinely different things. Temperature is a measure of how hot or cold something is — a property an object simply has. Heat is energy on the move, flowing from a hotter object to a colder one because of a temperature difference between them.
A large pot of lukewarm water and a small cup of very hot tea can contain the same total amount of thermal energy, or even have the water hold more, despite the tea being at a much higher temperature — temperature doesn't care how much material there is, but the total energy stored very much does.
Once two objects reach the same temperature, heat flow between them stops, even though both still have plenty of thermal energy. That's the point of "same temperature": it means there's no more temperature difference left to drive further heat flow, not that either object has run out of energy.
Key ideas
Requires: Physical quantities and units
Unlocks: Kinetic theory of gases, Specific heat capacity, Thermal expansion
Common misconceptions
- Temperature and heat are the same physical quantity.
- Two objects at the same temperature always feel equally warm or cold to the touch.
- Heat always flows from a larger object to a smaller one, regardless of their temperatures.