Curriculum
Science — Second Preparatory
Unit 1: Matter and Energy
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Unit 2: Matter and Chemical Reactions
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Unit 3: Energy Flow in Photosynthesis and Respiration
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Unit 4: Geological Processes
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Text lesson
Changes of State
Changes of State
Constant temperature during a change of state
Constant temperature during a change of state
- When ice below 0 °C is heated, its temperature rises until it reaches 0 °C.
- Then melting starts, and the temperature stays at 0 °C until the last piece of ice has melted.
- The heat gained during this stage is used to separate the particles from each other, not to raise the temperature.
- In the same way, pure water boils at 100 °C under normal atmospheric pressure, and its temperature stays constant while it boils.
- The heat needed to change the state without changing the temperature is called the latent heat.
- The latent heat of fusion of ice is 336 kJ per kilogram.
- The latent heat of vaporisation of water is 2260 kJ per kilogram.
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