Water and Changes of State

1. Water and Changesof State

2. Joe is buying ice kachang …

3. but when he reached home … My ice kachang is all watery and slushy. What happened?

4. Why did this happen?

5. ice (solid) It has definite shape and volume. water (liquid) It has definite volume but no definite shape. steam, water vapour (gas) It has no definite shape and volume. 3 states of water

6. water loses heat ice Freezing • When you put water into the freezer, water loses heat. • At 0oC, water freezes to become ice. 0oC is the freezing point of water.

7. It gains heat from the surroundings and its temperature rises to 0oC. • At 0oC, ice melts to become water. Melting • When ice is just taken out of the freezer, the temperature of ice is lowerthan 0oC. 0oC is also called the melting point of ice.

8. ice gains heat water Melting • During the process of melting, the ice gains heat but its temperature remains at 0oC. • The heat taken in is used to change the solid ice to liquid water.

9. water gains heat steam Boiling • When water is boiled, it gains heat. • When the water’s temperature reaches 100oC, water boils to become steam. 100oC is called the boiling point of water.

10. water boils at 100oC water freezes at 0oC ice melts at 0oC

11. water gains heatwater vapour Evaporation • Water on the wet clothes gains heat from the surroundings. • The water evaporates to become water vapour and escapes into the air. Evaporation occurs all the time and at any temperature.

12. Factorsaffecting the rate of evaporation temperature area of exposed surface wind humidity

13. The higher the temperaturethe higher the rate of evaporation

14. The stronger thewindthe higher the rate of evaporation

15. The larger thearea of exposed surfacethe higher the rate of evaporation

16. The air in the jungle is humid. So Sue’s sweat evaporates slowly. The air in the desert is dry. So Joe’s sweat evaporates quickly. The lower the humiditythe higher the rate of evaporation

17. The water vapour in the air loses heat and condenses (to become water) on the surface of the glass. water vapourloses heatwater Condensation • The cool surface of the glass cools the air surrounding it. Condensation can take place at any temperature.

18. steam loses heatwater Condensationat higher temperatures • As steam loses heat, it condenses to become water. • The white “clouds” (that you see) are tiny water droplets. clouds

19. solid (ice) liquid (water) gas (steam, water vapour) Losing heat condensation freezing

20. solid (ice) liquid (water) gas (steam, water vapour) Gaining heat evaporation / boiling melting

21. What happens when other things gain heat?

22. Candles are made from wax.Wax melts when it gains heat. candles

23. Butter melts when it gains heat. butter

24. The alcohol on these swabs evaporates easily when it gains heat. alcohol

25. Perfumes are liquids that evaporate easily when they gain heat. perfumes

26. solid (ice) liquid (water) steam, water vapour (gas) 3 states of water

27. At a glance … • Water freezes into ice at 0OC. This is called the freezing point of water. • Ice melts into water at 0OC. This is called the melting point of water. • Water boils and produces steam at 100OC. This is called the boiling point of water.

28. At a glance … • Water evaporates into water vapour at any temperature. • Steam or water vapour condenses to become water.