GCSE Combined Science (AQA)

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Specific Latent Heat

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Particle model of matter Internal energy and energy transfers

Specific Latent Heat

2:40 Heating to Change State
Spec 4.3.2.3
Previous Heating & Change of State Next Calculating Energy to Change State
  • Specific latent heat is the energy required to change the state of one kilogram of a substance without a change in temperature.
  • Example: 2.26 megajoules of heat is needed to boil one kilogram of water at 100 degrees Celsius.
  • Thermal energy used to boil water is transferred to the internal energy of the steam produced.
  • Temperature remains constant during the change of state but increases if heating continues afterward.
  • Specific latent heat of fusion describes changes from solid to liquid (e.g., ice to water).
  • Specific latent heat of fusion for water is 334 kilojoules to melt one kilogram of ice into water.
  • Specific latent heat of vaporization describes changes from liquid to gas.
  • Specific latent heat of vaporization for water is 2.26 megajoules to boil one kilogram of water into steam.
  • Avoid mixing up definitions of latent heat as it could result in losing marks in exams.
  • Latent heat can be measured by recording energy given to a heater during the change of state.
  • An electronic heater is used for faster heating than heat flow from surroundings.
  • When ice melts, the liquid flows through a funnel into a beaker, and the change in mass is recorded.
  • The mass of melted ice is the same as the mass of water collected.
  • Energy used for heating is determined by the electrical power of the heater.
  • Latent heat is calculated by dividing the energy by the mass.
  • Familiarity with this experiment or similar ones is recommended for exams.

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