water

• aim - describe how to analyse a sample of water for purity and how to purify a sample of water by distillation
• 1 - measure pH of water, by placing a small amount of water onto a piece of universal indicator paper. the paper will turn green if pH is 7 (neutral)
• 2 - if paper does not turn green then the water sample is not pure and contains dissolved acids or alkali
• 3 - even if pH is 7, water still may not be pure and contains dissolved solids. we need to test for those
• 4 - use a balance to weigh an empty evaporating basin and record mass
• 5 - fill evaporating basin with water sample and place on a tripod and gauze. use a bunsen burner to gently heat the water until all has evaporated. let basin cool and weigh again
• 6 - if the water basin contained any dissolved solids, then the mass of the empty evaporating basin would have increased because the dissolved solids would of formed crystals on the surface of the basin