Pure Substances
Science: KS3, topic 2.1.14
Pure Substances
Substances can be pure or impure. Pure substances are important in chemistry. Impure substances can affect the results of a practical experiment.
Purity
- Pure substances only contain one type of atom, element or compound.
- Impure substances contain other atoms.
- Impure substances are a mixture.
- If a substance contains impurities, the boiling or melting point will change.
Adding salt to ice
- We use salt to melt ice and snow.
- Salt makes the ice more impure.
- Impure ice has a lower melting point.
- The impure ice melts at a lower temperature.
Test yourself on Pure Substances
Which of these can be added to snow in order to melt the snow?
A student has two identical ice cubes. One is pure ice and the other has salt mixed into it, making it impure ice. Which ice cube melts at a lower temperature, and why?