What you’ll learn7 learning objectivesChoose one objective for a focused lesson, or study the complete topic.10.1.1Chemical tests for the presence of• Describe chemical tests for the presence of water using anhydrous cobalt(II) chloride and anhydrous copper(II) sulfateSyllabus objective10.1.2To test for the purity of water using• Describe how to test for the purity of water using melting point and boiling pointSyllabus objective10.1.3Distilled water is used in practical• Explain that distilled water is used in practical chemistry rather than tap water because it contains fewer chemical impuritiesSyllabus objective10.1.4Substances found in natural water• State substances found in natural water: dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, fertiliser nitrates, and phosphates from fertilisers/detergentsSyllabus objective10.1.5Some of these substances are• State: some of these substances are beneficial, (a) dissolved oxygen for aquatic life (b) some metal compounds provide essential minerals for lifeSyllabus objective10.1.6Harmful substances: toxic metal• State harmful substances: toxic metal compounds, plastics harming aquatic life, sewage microbes causing disease, and nitrates/phosphates causing deoxygenation and aquatic damage. Eutrophication details not requiredSyllabus objective10.1.7Treatment of the domestic water supply• Describe treatment of the domestic water supply in terms of: (a) sedimentation and filtration to remove solids (b) use of carbon to remove tastes and odours (c) chlorination to kill microbesSyllabus objective