Testing Water Purity
Chemistry: Edexcel IGCSE, topic 13.2.12
Testing Water Purity
We can test the purity of water by evaporating it on an evaporating dish or by by measuring its boiling point.
Evaporation
- If water contains dissolved salts, these salts will be left behind when water evaporates.
- The purer the water is, the less salts are left behind.
- Pure water will leave nothing behind.
Boiling point
- Pure water melts at 0°C and boils at 100°C.
- If the water contains impurities:
- The melting point will be higher than 0°C.
- The boiling point will be lower than 100°C.
- We can find out how many impurities a water sample contains by working out how far from these temperatures the sample melts or boils.
- The greater the number of impurities, the further away from these temperatures the sample will melt or boil.
Test yourself on Testing Water Purity
What temperatures does pure water melt and boil at?
Which of these is not a method for testing water purity?