Matter is a physical substance that occupies space and has mass. According to the particle theory, all matter is made up of particles. The particle model is proposed to describe the arrangement of particles in the three states of matter. The particle theory can be used to explain the properties of matter in different states, and some physical phenomena like thermal expansion and contraction, the existence of gas pressure, dissolving and whether an object floats or sinks.

 

In this Unit, students will be introduced to some basic ideas of particle theory and learn to use it to explain some physical phenomena. Through performing different practical works, e.g. observing the movement of particles in a smoke cell under a microscope and measuring the change in volume and mass when salt is dissolved in water, students will practise different science process skills like observing and inferring. Learning about the particle theory and using the theory to explain physical phenomena helps students realise the unifying concept “evidence and models”.