Heat is a form of energy that flows from a hotter body to a colder one. Temperature measures how hot or cold an object is. The two are different but related, and the topic is important for general science exams.
Difference Between Heat and Temperature
- Heat is total thermal energy; its SI unit is the joule.
- Temperature is the average energy of particles; its SI unit is kelvin (K).
- Heat is measured by a calorimeter; temperature by a thermometer.
Temperature Scales
- Celsius: water freezes at 0 and boils at 100.
- Fahrenheit: water freezes at 32 and boils at 212.
- Kelvin is the SI scale; 0 K = -273 degree Celsius (absolute zero).
- Normal human body temperature is about 37 degree Celsius (98.6 F).
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Modes of Heat Transfer
- Conduction: heat flows through solids without the material moving.
- Convection: heat flows through liquids and gases by movement of particles.
- Radiation: heat flows without any medium, like heat from the Sun.
Specific Heat and Effects of Heat
- Specific heat is the heat needed to raise 1 kg of a substance by 1 degree.
- Water has a very high specific heat.
- Heat causes expansion of solids, liquids and gases.
Quick Revision Points
- SI unit of heat is joule; of temperature is kelvin.
- Absolute zero = 0 K = -273 degree C.
- Body temperature is about 37 degree C.
- Conduction in solids, convection in fluids.
- Radiation needs no medium.
- Sun's heat reaches Earth by radiation.
- Water has high specific heat.