How to Test for Water (Edexcel IGCSE Chemistry (Modular))

Test for water

• Water can be identified using a chemical test and/or a physical test

Chemical test for water

• Anhydrous copper(II) sulfate turns from white to blue on the addition of water

• The equation is:

CuSO₄ (s) + 5H₂O (l) → CuSO₄.5H₂O (s)

Copper sulfate turns a light blue colour in the presence of water

Physical test for water

• A physical test to see if a sample of water is pure is to check its boiling point

• A sample of the liquid is placed in a suitable container such as a boiling tube and gently heated

• Using a thermometer, you can check if the boiling point is exactly 100 ^oC

• Any impurities present will usually tend to raise the boiling point and depress the melting point of pure substance