States of matter: Basics
Check out this PhET simulation on states of matter to explore how the particles behave during changes of state.
Physical and chemical changes
Matter is dynamic in nature. Explore how it undergoes physical and chemical changes, including transformations between different states such as melting, freezing, and evaporating.
Physical change
A physical change is when the substance changes its physical appearance or state without affecting its chemical identity. Examples of physical changes include:
- the grating of a piece of cheese
- the boiling of water
- sugar dissolving in water.
Change of state
When a substance converts from one physical state to another, this is known as a change of state. Let's look at changes of state using water as an example.
Water is one of the few substances that can exist in all three states: solid ice, liquid water, and gaseous steam or vapour. The process of state changes have different names depending on which states are involved.
- Melting is when a solid changes to liquid.
- Freezing is when a liquid changes to solid.
- Condensation is when a gas changes to liquid.
- Vaporisation is when a liquid changes to gas.
- Deposition is when a gas changes to solid.
- Sublimation is when a solid changes to gas.
Changing states of matter image, by RMIT, licensed under CC BY-NC 4.0
Chemical change
A chemical change is when a substance changes its chemical identity or composition. It involves the formation of new substances that have different properties compared to the original substance. Examples of chemical changes include:
- the rusting of iron objects when exposed to moist air for a long period of time
- sugar heated in a saucepan to make caramel
- the burning of potassium in water
- milk turning sour.
Your turn – physical and chemical changes
Test yourself on your understanding of physical and chemical changes.
