Particle model of matter

The particle model of matter is a fundamental concept in physics that explains how all substances are made up of tiny particles (atoms, molecules, or ions) in constant motion. This model helps us understand the properties of solids, liquids, and gases, and how they change state when heated or cooled. In the WJEC GCSE Combined Science course, you'll explore how the arrangement and movement of particles determine density, pressure, and energy transfers during changes of state.

Understanding the particle model is crucial because it links microscopic behaviour to macroscopic observations. For example, it explains why ice floats, why a gas exerts pressure on its container, and why heating a solid eventually turns it into a liquid. This topic also introduces key equations, such as density = mass/volume, and the concept of internal energy. Mastering this model will help you tackle more advanced topics like thermodynamics and kinetic theory later in your studies.

In the wider subject of Combined Science, the particle model connects to chemistry (states of matter, diffusion) and physics (energy, forces). It's a core idea that appears in many exam questions, often requiring you to explain everyday phenomena using particle theory. By the end of this topic, you should be able to describe the arrangement and motion of particles in each state, calculate density, and explain how energy is involved in changes of state.