To confirm that a colourless liquid is pure water, you can:
- Measure its boiling point. Pure water boils sharply at 100°C (373 K) at standard atmospheric pressure.
- Measure its freezing (melting) point. Pure water freezes sharply at 0°C (273 K) at standard atmospheric pressure.
- Conduct a chemical test like adding anhydrous copper (II) sulfate, which turns blue in the presence of water.
If the liquid boils at 100°C and freezes at 0°C under 1 atmosphere pressure and shows chemical behavior consistent with water, it can be confirmed as pure water.
