Thermal physics

Thermal physics is the study of heat, temperature, and the transfer of energy between systems. In the WJEC A-Level Physics specification, this topic covers the behaviour of gases, the laws of thermodynamics, and the concepts of internal energy, specific heat capacity, and latent heat. Understanding thermal physics is essential for explaining phenomena from the operation of heat engines to the cooling of a cup of tea, and it forms the foundation for more advanced topics in thermodynamics and statistical mechanics.

This topic is central to physics because it links microscopic particle behaviour to macroscopic observables like pressure and temperature. You will explore the kinetic theory of gases, which explains how gas pressure arises from molecular collisions, and the ideal gas law, which relates pressure, volume, and temperature. The first law of thermodynamics introduces the conservation of energy in thermal processes, while the second law deals with the direction of heat flow and the concept of entropy. Mastering these ideas will enable you to solve problems involving energy transfers, efficiency, and the behaviour of real and ideal gases.

Thermal physics also has practical applications in engineering, meteorology, and everyday life. For example, understanding specific heat capacity helps in designing heating and cooling systems, while latent heat is crucial for understanding phase changes like boiling and condensation. In the WJEC exam, you will be expected to apply these concepts to both theoretical and experimental contexts, including the use of the gas laws and calorimetry experiments.