2. Chapter 6 Water and Humans

3. Water in Nature

4. State: Liquid(water) 、 Solid(ice) 、 Gas(steam) Space: in sea 、 in glacier 、 in air with salt: salt water 、 fresh water

5. Limited Fresh Water Water in sea holds 96.5% in total water source in earth. River,lake,and underground water belong to fresh water. People can use directly fresh water is limited.

6. We are in great need of water. Water is very important for human life. We must economize on the use of water.

7. soluble particles (e.g salt) insoluble particles (e.g mud and sand) Natural water is impure. It contain soluble particles,insoluble particles, and micro-- organisms. micro—organisms (e.g germ)

8. We can get pure water by some ways as follow:

9. 1. Settle Large particles can be removed by this way.

10. 2. Filtration Suspended or small particles can be removed by filtration.

11. Micro--organisms can be killed by boiling or adding chlorine. 3. Boiling or Adding Chlorine Water

12. Distillation is the best way to purify water. steam Impurity water Purity water out in 4. Distillation

13. Three States of Water

14. Water exists in 3 states:  Solid: ice  Liquid: water  Gas: steam

15. liquid solid gas melt sublimation boil liquefy condensation The 3 states are related as follow: freeze

16. The temperature at which a solid changes into a liquid is called the melting point.

17. Boiling of water The temperature at which a liquid changes into a gas is called the boilng point.

18. Evaporation

19. Compare to two pictures as follow: Surface Area???

20. Humidity 95% Humidity 65%

21. Moving Air???

22. Evaporation occurs at all temperatures. Evaporation can be enhanced by: Large surface area Higher temperature Moving air

23. Water Circulation in Nature

24. 5.3 水的循環 water drop C. cloud D. Rain falls E. Return to the rive 、 sea water in the river 、 sea A. B. steam Water Circulation evaporate condense amass rain

25. Prevent Water Pollution

26. The main reasons of water pollution: 1 、 water waste from living 2 、 water waste from farming 3 、 water waste from industry

27. 1 、 Industry Pollution 3 wastes: waste material waste liquid waste gas

28. 2 、 Farming Pollution Pollution make fish die Insecticide and chemical fertilizer give rise to water pollution.

29. Water Pollution Change Frog Shape

30. 3 、 Ocean Pollution Petroleum flow into the ocean, and cause the water pollution, a lot of birds die.

31. All citizens should prevent water pollution and the best way to do it is to reduce water waste from family using.