THERMAL PHYSICS — COMPLETE
NOTES
1. Introduction to Thermal Physics
Thermal physics is the study of heat, temperature, and how energy transfers between
objects. It connects two major physics ideas:
1. Energy (a quantity that can be transferred or transformed).
2. Matter (made of particles with motion and internal energy).
In IGCSE Physics, the aim is to understand how heat affects matter, how temperature changes
occur, and how energy moves from one place to another through conduction, convection, and
radiation.
2. Temperature vs Heat
Temperature — Definition
Temperature is a measure of the average kinetic energy of particles in a substance.
● Measured in degrees Celsius (°C) or Kelvin (K).
● A higher temperature means particles move faster.
Heat (Thermal Energy) — Definition
Heat is the transfer of thermal energy from a region of higher temperature to a region of lower
temperature.
● Measured in joules (J).
, ● Heat moves, temperature measures energy.
Key difference
● Temperature: depends on particle motion.
● Heat: depends on energy transferred, mass, and temperature difference.
3. Internal Energy
Every substance contains internal energy, which is the total of:
1. Kinetic energy of particles (motion).
2. Potential energy of particles (spacing/bonds).
When heat is added:
● Internal energy increases.
● This may change temperature OR state.
4. Kinetic Theory of Matter
The kinetic theory explains matter by describing particles:
Solids
● Particles vibrate in fixed positions.
● Strong forces of attraction.
● Fixed shape and volume.
Liquids
NOTES
1. Introduction to Thermal Physics
Thermal physics is the study of heat, temperature, and how energy transfers between
objects. It connects two major physics ideas:
1. Energy (a quantity that can be transferred or transformed).
2. Matter (made of particles with motion and internal energy).
In IGCSE Physics, the aim is to understand how heat affects matter, how temperature changes
occur, and how energy moves from one place to another through conduction, convection, and
radiation.
2. Temperature vs Heat
Temperature — Definition
Temperature is a measure of the average kinetic energy of particles in a substance.
● Measured in degrees Celsius (°C) or Kelvin (K).
● A higher temperature means particles move faster.
Heat (Thermal Energy) — Definition
Heat is the transfer of thermal energy from a region of higher temperature to a region of lower
temperature.
● Measured in joules (J).
, ● Heat moves, temperature measures energy.
Key difference
● Temperature: depends on particle motion.
● Heat: depends on energy transferred, mass, and temperature difference.
3. Internal Energy
Every substance contains internal energy, which is the total of:
1. Kinetic energy of particles (motion).
2. Potential energy of particles (spacing/bonds).
When heat is added:
● Internal energy increases.
● This may change temperature OR state.
4. Kinetic Theory of Matter
The kinetic theory explains matter by describing particles:
Solids
● Particles vibrate in fixed positions.
● Strong forces of attraction.
● Fixed shape and volume.
Liquids
