C4 - Purifying and testing water
- Created by: Naomi
- Created on: 23-01-13 21:42
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- Purifying and testing water
- Water purification
- The water in a river is cloudy and often not fit to drink
- To turn it into clean water in taps it is passed through a water purification works
- The three stages of water purification are:
- Sedimentation
- Chemicals are added to make solid particles and bacteria settle out
- Filtration
- A layer of sand on gravel filters out the remaining fine particles
- Some types of sand filter also remove microbes
- A layer of sand on gravel filters out the remaining fine particles
- Chlorination
- Chlorine is added to kill microbes
- Sedimentation
- Some soluble substances such as pesticides and nitrates are not removed by the standard purification method (as they are dissolved in water)
- Extra processes are needed to remove them
- Sea water has many sunstances dissolved in it that is undrinkable
- Techniques such as distillation must be used to remove the dissolved substances
- It takes huge amounts of energy, so it is very expensive and only used when there is no fresh water
- Techniques such as distillation must be used to remove the dissolved substances
- The water in a river is cloudy and often not fit to drink
- Water tests
- Water can be tested with precipitation reactions using aqueous silver nitrate solution and barium chloride solutions
- In precipitation reactions, two solutions react to form a chemical that does not dissolve
- This chemical suddenly appears in the liquid as a solid - a precipitate
- Water purification
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