The particle model

C1.1 The particle model

Summary This short section introduces the particle model and its explanation of different states of matter. A simple particle model can be used to represent the arrangement of particles in the different states of matter and to explain observations during changes in state. It does not, however, explain why different materials have different properties. This explanation is that the particles themselves and how they are held together must be different in some way. Elements are substances that are made up of only one type of atom and atoms of different elements can combine to make compounds. Underlying knowledge and understanding Learners should be familiar with the different states of matter and their properties. Learners should be aware of the energy changes when a change of state occurs. They should also be familiar with changes of state in terms of the particle model. Learners should have sufficient grounding in the particle model to be able to apply it to unfamiliar materials and contexts.

Common misconceptions Learners commonly intuitively adhere to the idea that matter is continuous. For example, they believe that the space between gas particles is filled or non- existent, or that particles expand when they are heated. The notion that empty space exists between particles is problematic because this lacks supporting sensory evidence. They also show difficulty understanding the concept of changes in state being reversible; this should be addressed during the teaching of this topic.