Specification Point 2.49:
Describe a test for the presence of water using anhydrous Copper (II) Sulfate

Chemical Test for Water

Test for water, Edexcel IGCSE Chemistry

Test for Water using Anhydrous Copper (II) Sulfate


  • Add liquid to anhydrous copper (II) sulfate
  • Colour change is observed and recorded


  • If liquid is water, the white powder will turn blue
  • This is because hydrated copper (II) sulfate is formed and is a blue crystal
  • Does not indicate whether water is pure


  CuSO4 (s)      +         5H2O  (l)      →         CuSO4.5H2O (s)      

    White                                                              Blue           

Specification Point 2.50:
Describe a physical test to show whether a sample of water is pure

Physical Test for Pure Water

Physical Test for Pure Water, Edexcel IGCSE Chemistry

The process to measure the boiling point of water


  • Boil the liquid and measure temperature as liquid starts to boil – its boiling point
  • Freeze the liquid to measure its freezing point (same as melting point)


  • Boiling point of pure water is 100°C
  • Freezing point (melting point) of water is 0°C
  • If either are increased or decreased water sample contains impurities

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.