IGCSE Coordinated Science: Chemical and Physical Changes 1. Identify physical and chemical changes, and understand thedifferences between them. Chemical Changes : These occur when a substance combines with another to form a new substance Examples include: ❖ Rotting fruit ❖ Mixing chemicals ❖ Tarnishing silver. Physical changes: These are changes that affect the form of an object, but ultimately doesn’t have any effect on its chemical composition. Examples include : ❖ Tearing a piece of tin foil. ❖ Crumpling a piece of paper. Differences between the two: 1. A physical change is reversible, a chemical change is not. Forexample, the freezing of water would be a physical change because itcan be reversed, whereas the burning of wood is a chemical change –you can’t ‘unburn’ it 2. A physical change is a change in which no new substance is formed;a chemical change results in the formation of one or more newsubstances. Again, consider the previous examples: Freezing water intoice just results in water molecules which are ‘stuck’ together – it’s stillH 2 O. Whereas burning wood results in ash, carbon dioxide, etc, all new substances which weren’t there when you started.
You’re messing around with the physical structure object, but that’s it.