Topic 2 of 6 · 3 of 6 modules ready

Thermal physics

The particle model of matter and how heating changes temperature, state and size.

Modules

Module 2 · syllabus 2.1.2, 2.1.3, 2.2.1 · 3 parts
Gas pressure and temperature
Why can a sealed can burst when it gets hot?
Trap some air in a syringe joined to a pressure gauge and squeeze it to smaller and smaller volumes, with a magnifier showing a model of its particles. Then lock the plunger, cool the air with ice and warm it on a hotplate, and extend the graph to find where the pressure would reach zero.
1. Squeezing a gas Gas pressure from particles hitting the walls, as a force per unit area; squeezing a gas at a steady temperature, and pV = constant with its graphs
2. Heating a gas at a fixed volume Heating a gas at a fixed volume, in particle terms; the kelvin scale and T = θ + 273
3. Thermal expansion Thermal expansion of solids, liquids and gases, why gases expand most, and where expansion is useful or a problem
Experiment Squeeze trapped air · then lock it, cool it and warm it
Open module Experiment Teacher pack

Module 2 · syllabus 2.1.2, 2.1.3, 2.2.1 · 3 parts

Gas pressure and temperature

Why can a sealed can burst when it gets hot?

Trap some air in a syringe joined to a pressure gauge and squeeze it to smaller and smaller volumes, with a magnifier showing a model of its particles. Then lock the plunger, cool the air with ice and warm it on a hotplate, and extend the graph to find where the pressure would reach zero.

Squeezing a gas Gas pressure from particles hitting the walls, as a force per unit area; squeezing a gas at a steady temperature, and pV = constant with its graphs
Heating a gas at a fixed volume Heating a gas at a fixed volume, in particle terms; the kelvin scale and T = θ + 273
Thermal expansion Thermal expansion of solids, liquids and gases, why gases expand most, and where expansion is useful or a problem

Experiment Squeeze trapped air · then lock it, cool it and warm it

Open module Experiment Teacher pack

Syllabus statements for this topic · for teachers · 45 statements

Core for every pupil · Supplement also for Extended entry. Paraphrased from the Cambridge IGCSE Physics 0625 syllabus (2026–2028); check the official syllabus for exact wording.

2.1.1 States of matter

2.1.1.1Properties of solids, liquids and gasesC
2.1.1.2Names of the changes of stateC

2.1.2 Particle model

Covered in Gas pressure and temperature

2.1.2.1Particle arrangement, separation and motion; particle diagramsC
2.1.2.2Particle motion, temperature and absolute zeroC
2.1.2.3Gas pressure from particle collisions with wallsC
2.1.2.4Random motion of suspended specks supports the particle modelC
2.1.2.5Brownian motion explained by random molecular collisionsC
2.1.2.6Particle forces, distances and motion set propertiesS
2.1.2.7Gas pressure as collision force per unit areaS
2.1.2.8Fast light molecules move visible specks; atoms versus specksS

2.1.3 Gases and the absolute scale of temperature

Covered in Gas pressure and temperature

2.1.3.1Gas pressure with temperature or volume, in particle termsC
2.1.3.2Kelvin and Celsius; T = θ + 273C
2.1.3.3pV = constant at fixed temperature, with its graphS

2.2.1 Thermal expansion of solids, liquids and gases

Covered in Gas pressure and temperature

2.2.1.1Thermal expansion of solids, liquids and gasesC
2.2.1.2Everyday uses and problems of thermal expansionC
2.2.1.3Why gases expand most and solids leastS

2.2.2 Specific heat capacity

Covered in Specific heat capacity

2.2.2.1Temperature rise increases internal energyC
2.2.2.2Temperature rise as higher average particle kinetic energyS
2.2.2.3Specific heat capacity; c = ΔE/(mΔθ)S
2.2.2.4Measuring specific heat capacity of a solid and liquidS

2.2.3 Melting, boiling and evaporation

Covered in Melting, boiling and evaporation

2.2.3.1Melting and boiling: energy in, temperature steadyC
2.2.3.2Melting and boiling points of waterC
2.2.3.3Condensation and solidification in particle termsC
2.2.3.4Evaporation as escape of faster surface particlesC
2.2.3.5Evaporation cools the remaining liquidC
2.2.3.6Boiling versus evaporationS
2.2.3.7Temperature, surface area and airflow affect evaporationS
2.2.3.8Cooling an object by an evaporating liquidS

2.3.1 Conduction

2.3.1.1Experiments comparing thermal conductors and insulatorsC
2.3.1.2Conduction by lattice vibrations and free electronsS
2.3.1.3Why gases and most liquids conduct poorlyS
2.3.1.4Many solids conduct moderately wellS

2.3.2 Convection

2.3.2.1Convection transfers energy in liquids and gasesC
2.3.2.2Convection from density changes; demonstration experimentsC

2.3.3 Radiation

2.3.3.1Thermal radiation is infrared; all objects emit itC
2.3.3.2Radiation transfer needs no mediumC
2.3.3.3Surface colour and texture versus infrared emission and absorptionC
2.3.3.4Steady temperature: energy out equals energy inS
2.3.3.5Unequal energy rates warm or cool an objectS
2.3.3.6Earth's temperature and its radiation balanceS
2.3.3.7Experiments comparing infrared emittersS
2.3.3.8Experiments comparing infrared absorbersS
2.3.3.9Emission rate with surface temperature and areaS

2.3.4 Consequences of thermal energy transfer

2.3.4.1Everyday transfers: pans and room heatingC
2.3.4.2Combined transfers: coal fire, car radiatorS