Revision

Objectives

Lesson outcomes

Retrieve the key definitions, equations, and assumptions across A2 thermal physics.
Practise mixed questions involving temperature, thermal energy, ideal gases, kinetic theory, and the first law.
Identify which parts of the A2 topic need focused revision before the test.

Syllabus

CIE 9702 syllabus points

21 linked

14.1.1 understand that (thermal) energy is transferred from a region of higher temperature to a region of lower temperature
14.1.2 understand that regions of equal temperature are in thermal equilibrium
14.2.1 understand that a physical property that varies with temperature may be used for the measurement of temperature and state examples of such properties, including the density of a liquid, volume of a gas at constant pressure, resistance of a metal, e.m.f. of a thermocouple
14.2.2 understand that the scale of thermodynamic temperature does not depend on the property of any particular substance
14.2.3 convert temperatures between kelvin and degrees Celsius and recall that T / K = θ / °C + 273.15
14.2.4 understand that the lowest possible temperature is zero kelvin on the thermodynamic temperature scale and that this is known as absolute zero
14.3.1 define and use specific heat capacity
14.3.2 define and use specific latent heat and distinguish between specific latent heat of fusion and specific latent heat of vaporisation
15.1.1 understand that amount of substance is an SI base quantity with the base unit mol
15.1.2 use molar quantities where one mole of any substance is the amount containing a number of particles of that substance equal to the Avogadro constant NA
15.2.1 understand that a gas obeying pV ∝ T, where T is the thermodynamic temperature, is known as an ideal gas
15.2.2 recall and use the equation of state for an ideal gas expressed as pV = nRT, where n = amount of substance (number of moles) and as pV = NkT, where N = number of molecules
15.2.3 recall that the Boltzmann constant k is given by k = R / NA
15.3.1 state the basic assumptions of the kinetic theory of gases
15.3.2 explain how molecular movement causes the pressure exerted by a gas and derive and use the 1 1
15.3.3 understand that the root-mean-square speed cr.m.s. is given by <c 2 > 1
15.3.4 compare pV = 3 Nm<c2> with pV = NkT to deduce that the average translational kinetic energy of a 3
16.1.1 understand that internal energy is determined by the state of the system and that it can be expressed as the sum of a random distribution of kinetic and potential energies associated with the molecules of a system
16.1.2 relate a rise in temperature of an object to an increase in its internal energy
16.2.1 recall and use W = p∆V for the work done when the volume of a gas changes at constant pressure and understand the difference between the work done by the gas and the work done on the gas
16.2.2 recall and use the first law of thermodynamics ∆U = q + W expressed in terms of the increase in internal energy, the heating of the system (energy transferred to the system by heating) and the work done on the system

Definitions

Required definitions

Specific heat capacity
the energy required per unit mass per unit temperature rise.
Specific latent heat
the energy required per unit mass to change state without a change in temperature.
Specific latent heat of fusion
the energy required per unit mass to change between solid and liquid without a change in temperature.
Specific latent heat of vaporisation
the energy required per unit mass to change between liquid and gas without a change in temperature.

Lesson Notes

Student guidance and lesson notes

Overview

This lesson brings the whole A2 thermal physics sequence together before assessment. You should be able to move between temperature scales, thermal energy calculations, the ideal gas equation, kinetic theory, internal energy, and the first law without treating them as separate checklists.

What You Need to Know

Temperature and thermal equilibrium explain the direction of thermal energy transfer.
Thermal energy questions depend on recognising whether the process is heating, cooling, changing state, or mixing systems.
Ideal gas questions require kelvin temperatures and careful distinction between n and N.
Kinetic theory links pressure to molecular collisions and temperature to average translational kinetic energy.
Thermodynamics questions depend on a clear system, sign convention, and energy accounting.

How to Work Through It

Start with quick retrieval of definitions, assumptions, and equations from chapters 14-16.
Work through mixed past-paper questions without sorting them by lesson first.
Mark each response for physics reasoning, equation choice, unit conversion, and sign convention.
Finish by writing a short target list for the topic test.

Check Your Understanding

Can you choose between E = mc delta theta, E = mL, pV = nRT, pV = NkT, and delta U = q + W?
Can you explain pressure using molecular collisions rather than only quoting an equation?
Can you keep kelvin temperatures, SI volumes, and thermodynamic signs consistent?
Can you describe the difference between thermal energy, temperature, and internal energy?

Common Mistakes

Revising equations without practising when each model applies.
Losing marks through Celsius temperatures, non-SI volumes, or grams instead of kilograms.
Mixing up n, N, moles, molecules, molecule mass, and total gas mass.
Treating work done by a gas and work done on a gas as the same sign.