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What is temperature?

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Quick answer

Temperature is a measure of how hot or cold something is — specifically, the average energy of the particles moving inside it. The faster its particles move, the higher its temperature. It's measured in degrees Celsius, Fahrenheit, or kelvin. Temperature reflects the average kinetic energy of an object's particles.

Key things to understand

  1. Temperature reflects the average kinetic energy of an object's particles.
  2. Faster-moving particles mean a higher temperature.
  3. It's measured in Celsius (°C), Fahrenheit (°F), or kelvin (K).
  4. It differs from heat: temperature is how hot something is; heat is the energy that flows between things.
  5. The lowest possible temperature is absolute zero (−273.15°C), where particle motion is minimal.

People also ask

What's the difference between temperature and heat?
Temperature is how hot or cold something is — the average energy of its particles. Heat is the total thermal energy that flows from a hotter object to a cooler one. They're related but not the same.
What is absolute zero?
Absolute zero (−273.15°C, or 0 kelvin) is the lowest possible temperature, where particles have the least possible motion. It can be approached but never fully reached.
Why are there different temperature scales?
Celsius and Fahrenheit were set using different reference points; kelvin starts at absolute zero and is used in science for its simplicity.

Part of the guide: Everyday Science: Light, Heat & Matter →