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gcse science C4 - H
specific for ocr gateway additonal science B.
| Question | Answer |
|---|---|
| what are 4 different water sources? | -rivers -lakes -bore holes -reservoirs |
| what are the 3 ways in which water is used? | -coolant -valuable solvent -cheap raw material |
| what are 4 substances which pollute water and how do they get to the water supply? | -nitrate residues, nitrates from fertiliser -lead compounds, older houses have lead water pipes, lead dissolved into water -pesticide residues, spraying near to water sources |
| how is clean water made? | its passed through a water purification works |
| what are the tree main stages to water purification? | 1. sedimentation. larger solid particles settle out 2. filtration. sand used to filter out fine particles 3. chlorination. chlorine added to kill microbes |
| what poisonous soluble substances can still remain in the water? | pesticides and nitrates |
| how can these poisonous soluble substances be removed? | extra processes e.g. distillation |
| why would distillation of sea water be impractical? | uses huge amounts of energy, making it very expensive |
| why is clean water important? | saves more lives than medicine |
| why will a dry winter result in water shortages? | reservoirs don't fill up properly for the rest of the year |
| why is there an increase in demand for water? | more homes are being built |
| why can saving tap water reduce carbon dioxide emissions? | takes energy to pump and purify it |
| water tests: sulphate | lead nitrate + sodium sulphate - lead sulphate (white precipitate) + sodium nitrate Pb(NO3)2 + Na2SO4 - PbSO4 + 2NaNo3 |
| water tests: chloride | silver nitrate + sodium chloride - silver chloride (white precipitate) + sodium nitrate AgNO3 + NaCl - AgCl + NaNO3 |
| water tests: bromide | silver nitrate + sodium bromide - silver bromide (cream precipitate) + sodium nitrate AgNo3 + NaBr - AgBr + NaNO3 |
| water tests: iodide | silver nitrate + sodium iodide - silver iodide (yellow precipitate) + sodium nitrate AgNO3 + NaI - AgI + NaNO3 |
Created by:
jirwin
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