Thermal properties of matter · revision map · IGCSE 0625, Topic 2.2
TOPIC 2.2 · THERMAL PROPERTIES
CAMBRIDGE IGCSE PHYSICS 0625 · ONE-PAGE REVISION MAP
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THERMAL
PROPS2.2
PROPS2.2
Thermal Expansion
Heating makes particles vibrate more and move a little further apart, so most materials expand. Cooling makes them contract.
- Gases expand most, then liquids, then solids, for the same temperature rise.
- Used in liquid-in-glass thermometers, where the liquid rises up a narrow tube.
- Expansion gaps are left in bridges and railway lines so they are not damaged.
- A bimetallic strip bends as one metal expands more than the other; used in thermostats.
Specific Heat CapacityEXTENDED
The energy needed to raise the temperature of 1 kg of a substance by 1 °C (or 1 K).
E = m c Δθ
E = energy (J)
m = mass (kg)
c = specific heat capacity
Δθ = change in temperature
unit J/(kg · °C)
m = mass (kg)
c = specific heat capacity
Δθ = change in temperature
unit J/(kg · °C)
- A high specific heat capacity means a substance needs a lot of energy to warm up. Water has a high value.
- Found by heating a known mass with an electric heater and measuring the energy supplied and the temperature rise.
- Rearrange to find any quantity, for example c = E ÷ (m Δθ).
- Water's high value lets it store a lot of energy, so it is used in central-heating systems and keeps coastal climates mild.
Melting, Boiling & Latent Heat
During a change of state the temperature stays constant: energy goes into breaking bonds, not raising temperature.
E = m LL = specific latent heat (Extended)
melting/freezing at melting point;
boiling/condensing at boiling point
melting/freezing at melting point;
boiling/condensing at boiling point
Evaporation & CoolingEXTENDED
Evaporation happens from the surface of a liquid at any temperature, not just at boiling.
- The fastest molecules leave, so the average energy left falls and the liquid cools.
- Faster when hotter, with more surface area, a draught, and drier (less humid) air.