Key learning points

1. There are changes in arrangement, movement and energy of particles during state changes.
2. There are two types of change; physical and chemical, and the physical state of a substance can be predicted.
3. The attraction between particles has a role in determining the amount of energy needed for state changes.
4. The particle model has limitations, for example by showing particles as same sized, inelastic spheres.
5. The model does not show the attraction between the particles which affects the amount of energy needed to change state.

Keywords

• Physical change - A change in which no new substances are formed, such as a change in state, e.g. melting.

• Chemical change - Occurs when a reaction takes place and atoms or ions in the reactants are rearranged to make new products/substances.

• Particle model - A model that helps us to understand physical properties of substances. It uses circles or spheres to represent particles, i.e. atoms or compounds.

• Limitation of a model - A point at which we cannot use the model to help us explain a scientific phenomena.

Common misconception