ChemistryCode 5070
Water
What this topic asks you to be able to do
- Describe the chemical tests which reveal whether water is present, making use of anhydrous cobalt(II) chloride and anhydrous copper(II) sulfate
- Describe the procedure for checking how pure water is by measuring its melting point and its boiling point
- Account for the use of distilled water in practical chemistry in preference to tap water, given that it contains fewer chemical impurities
- State that water drawn from natural sources can have substances in it, including: sewage, plastics, harmful microbes, metal compounds, dissolved oxygen, nitrates from fertilisers, and phosphates from fertilisers and detergents
- State that, among these substances, some are beneficial, including: some metal compounds, which supply minerals essential for life, and dissolved oxygen, which aquatic life depends on
- State that a number of these substances can do harm, including: certain metal compounds, which are toxic; certain plastics, which harm aquatic life; sewage, which carries harmful microbes that cause disease; and nitrates and phosphates, which lead to deoxygenation of the water and harm to aquatic life
- Describe the treatment applied to the domestic water supply, with reference to: sedimentation and filtration to take out solids, carbon used to take out tastes and odours, chlorination to destroy microbes