Category Archives: 3.2 Water

Purifying water

Reasons for water of the correct quality  Water of the correct quality is essential for life. For humans, drinking water should have sufficiently low levels of dissolved salts and microbes. Producing water of the correct quality ■ choosing an appropriate source ■ passing the water through filter beds to remove any solids ■ sterilising with chlorine. Addition of chlorine and fluoride ions to drinking

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Hard and soft water

Reaction with soap Soft water readily forms lather with soap. Hard water reacts with soap to form scum and so more soap is needed to form lather: the presence of calcium ions and magnesium ions in the water makes it hard. Soapless detergents do not form scum with hard water. Origin of scum (hard water + soap) Hard water contains dissolved calcium or

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