1. Water Treatment

2. Stages in water treatment
Screening
Settling
Filtration
Chlorination
Fluoridation

3. Screening
Removes any floating material

4. Settling
Add aluminium sulfate to water. Small particles sink to the bottom of tank.

5. Filtration
Water is passed through beds of sand and removes insoluble particles. Water is now clear.

6. Chlorination
Add chlorine to water to kill bacteria.

7. Fluoridation
Add fluorine to water to prevent tooth decay.

8. Water Cycle

9. Electrolysis of water

10. Electrolysis of water
Electrolysis is the splitting of water by passing electricity through it.
A hoffmann voltameter is used to split water into hydrogen and oxygen.

11. Electrolysis of water
Add sulfuric acid to improve the conductivity of water to help to split the water.
Result:
There is twice as much hydrogen as there is oxygen.

12. Tests
Hydrogen: Burns with a pop Oxygen: relights with a glowing splint.

13. To demonstrate that water expands when heated
Water expands once it drops below 4 degrees celsius.

14. The meniscus
Curved surface of a liquid in a container.

15. Desalination
97% of all water is salt water.

16. Colourless, odourless liquid
Freezing point is 0oC
Excellent solvent
Properties of water
Colourless, odourless liquid
Boiling point 100oC

17. To show that water contains a dissolved substances
Step 1:
Filter the water to remove any insoluble substances

18. Step 2
Evaporate the water using the evaporation technique and check what materials are left behind.

19. How to remove water hardness:
Softening water involves removing the calcium and magnesium ions.
Methods of removing water hardness:
Boiling
Distillation
Ion exchange