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2.2.2Thermal Physics

Specific HEAT Capacity — Cambridge IGCSE Physics 0625 Revision Notes & Topical Questions

5 min read 8 parts Lesson 18 of 45 1 quiz

📚 Cambridge IGCSE Physics 0625 Hub / Topical Revision
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Lesson summary

2.2.2 Specific Heat Capacity — IGCSE PHYSICS notes: Define internal energy and specific heat capacity and use E = mcΔθ.Internal energy — the total energy stored inside a system by its particles due to their motion and positionsMotion of the particles gives kinetic energyRelative …

  • Temperature rise
  • Higher temperature
  • Definition
  • What the symbols mean
  • Electrical heater
  • Calculation

Part 1 of 6Internal energy

Internal energy
  • Internal energy the total energy stored inside a system by its particles due to their motion and positions
  • Motion of the particles gives kinetic energy
  • Relative positions of the particles give potential energy
  • The two together make up the internal energy
Temperature rise
  • Temperature rise raises the internal energy because the average speed of the particles increases

Part 2 of 6Temperature and average kinetic energy

Heating
  • Heating increases the kinetic energy of the particles and so the internal energy
Temperature
  • Temperature is related to the average kinetic energy of the molecules
Higher temperature
  • Higher temperature means a higher average kinetic energy of the particles

Part 3 of 6Specific heat capacity

1Definition
  • Definition specific heat capacity c is the energy required per unit mass per unit temperature increase
  • It is the energy needed to raise 1 kg of a substance by 1 °C
2Temperature rise depends on
  • Temperature rise depends on the mass heated, the type of material and the thermal energy transferred in
3Low c
  • Low c the substance heats up and cools down quickly
4High c
  • High c the substance heats up and cools down slowly
  • Water has a high c of about 4200 J/kg °C, so it is useful in heating systems and as a coolant

Part 4 of 6The equation

Equation
  • E = mcΔθ,
  • which rearranges to c = E ÷ (mΔθ)
    What the symbols mean: E, Q or q = energy transferred (J) · m = mass · c = specific heat capacity (J kg−1 °C−1; water 4.18 J g−1 °C−1) · ΔT or Δθ = temperature change (°C or K)
    • (kg; g in chemistry calorimetry)
  • E is the change in thermal energy in joules (J)
  • m is mass in kilograms (kg)
  • c is specific heat capacity in J/kg °C
  • Δθ is change in temperature in °C
Unit
  • J/kg °C means joules per kilogram per degree Celsius
Values
  • Values c is always given in an exam, so it need not be memorised

Part 5 of 6Measuring c in brief

Electrical heater
  • Electrical heater supplies energy E = IVt to a known mass in an insulated block or beaker
Calculation
  • Calculation c = E ÷
    • (m × temperature rise)
Heat loss
  • Heat loss energy lost to the surroundings makes the measured c too high
  • Reduce it by insulating and using a lid

Part 6 of 6More from the specification

1Specific heat capacity
  • Specific heat capacity energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius, with energy = mass x c x temperature change
2Electrical method
  • Electrical method an immersion heater in a block or liquid, with current and voltage measured, gives the energy supplied over time
3Changes of state
  • Changes of state melting, boiling and evaporation need energy to overcome forces between particles without a temperature rise
4Expansion
  • Expansion heating a solid, liquid or gas makes particles move more vigorously so the substance expands;
    • surface insulation reduces heat loss in the experiment
5Specific heat capacity
  • Specific heat capacity energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius, with energy = mass x c x temperature change
6Electrical method
  • Electrical method an immersion heater in a block or liquid, with current and voltage measured, gives the energy supplied over time
7Changes of state
  • Changes of state melting, boiling and evaporation need energy to overcome forces between particles without a temperature rise
8Expansion
  • Expansion heating a solid, liquid or gas makes particles move more vigorously so the substance expands;
    • surface insulation reduces heat loss in the experiment
9Constant
  • Not changing.
10Immersion heater
  • Electric heater placed in a liquid or block to supply energy
11Intermolecular force
  • An attractive force between particles.
12Potential difference
  • Work done by a unit charge passing through a component.
13Liquid
  • State with a fixed volume that takes the shape of its container.
14Evaporation
  • Escape of the most energetic molecules from a liquid surface at any temperature
15Boiling
  • Liquid becoming gas throughout the liquid at the boiling point
16Expansion
  • Increase in size on heating as particles move further apart.
17Melting
  • Change from solid to liquid.
18Force
  • A push or pull measured in newtons.
19Current
  • Flow of electrons in a circuit.
20Thermometer
  • A device that reaches equilibrium with an object to measure its temperature

Key terms

TermMeaning
Internal energyTotal kinetic and potential energy of the particles in a system
Specific heat capacityEnergy required per unit mass per unit temperature increase
Thermal energyEnergy transferred because of a temperature difference
J/kg °CUnit of specific heat capacity

Avoid these mistakes

1
Using grams instead of kilograms — convert mass to kg before using E = mcΔθ.
2
Thinking a high c heats up faster — a high c means more energy is needed per degree, so it heats slowly.
3
Confusing temperature with internal energy — temperature is linked to average kinetic energy, internal energy is the total of kinetic and potential energy.
4
Forgetting that heat loss makes the measured c too high — some supplied energy is not used to heat the sample.

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