Freezing, Melting, and Evaporation

1. Freezing, Melting, and Evaporation

2. Part 1 - Definitions • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

3. Melting To melt means to change a substance from a solid to a liquid state by heating it to the melting point. Different substances melt at different temperatures. Water melts at 0°C or 32°F.

4. Freezing To freeze means to change a substance from a liquid to a solid state by cooling it to the freezing point.

5. Temperatures • The freezing and melting temperatures for most substances are the same. • For water this is 0°C or 32°F. Read Workbook pages 180-181

6. Boiling Point The boiling point is the temperature at which a liquid changes to a vapor or gas. Again this is a different temperature for different substances. For water the boiling point is 100°C or 212°F.

7. Evaporation Evaporation is the change of a liquid into a vapor at a temperature below the boiling point. This occurs at any temperature between the melting point and the boiling point. However, the warmer the temperature the more quickly the water will evaporate.

8. Condensation Condensation is the change of a gas or vapor to a liquid, either by cooling it or by subjecting the substance to an increase in pressure. When water vapor cools in the atmosphere, it condenses into tiny drops of water which form clouds. Read Workbook page 187

9. Sublimation Sublimation is the process of changing from a solid to a gas without passing through a liquid phase. Read Workbook page 188

10. Practice – Number your paper from 1 to 10. Decide the state or phase for each item. Is it . . . • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

11. 1. In which state is the snow? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

12. 2. In which state is the puddle? (Choose 2 answers.) • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

13. 3. In which state is the fog? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

14. 4. In which state is the moisture on the bottle? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

15. 5. In which state is the puddle on the road? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

16. 6. In which state is the road? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

17. 7. In which state is the moisture on the leaf petals? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

18. 8. In which state is the water in the tea pot? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

19. 9. In which state is the ice next to the mountain? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

20. 10. In which state is the water vapor? • Melting • Freezing • Boiling • Evaporating • Condensing • Sublimating

21. Answers

22. 1. In which state is the snow? • Melting

23. 2. In which state is the puddle? • Melting • Freezing

24. 3. In which state is the fog? e) Condensing

25. 4. In which state is the moisture on the bottle? e) Condensing

26. 5. In which state is the puddle on the road? d) Evaporating

27. 6. In which state is the road? b) Freezing

28. 7. In which state is the moisture on the leaf petals? e) Condensing

29. 8. In which state is the water in the tea pot? c) Boiling

30. 9. In which state is the ice next to the mountain? f) Sublimating

31. 10. In which state is the water vapor? d) Evaporating

32. Part 2 Factors that influence the rate of Evaporation

33. Factor 1 - Temperature The higher the temperature the faster the rate of evaporation.

34. Which puddle will evaporate faster? A B

35. Factor 2 - Wind • The more wind or air circulation the faster the rate of evaporation.

36. Which puddle will evaporate faster?

37. Factor 3 – Exposed Surface Area The larger the exposed surface area the faster the evaporation rate. The water will evaporate more quickly from the beaker on the right with the wider opening. 1 inch 3 inches

38. If each beaker contains 8 ounces of water, which beaker will evaporate the quickest?

39. Factor 4 - Humidity • When humidity (the amount of water vapor in the air) is high, evaporation is slower.

40. In which location would laundry hanging on a line dry the quickest? Read Workbook page 189

41. Part 3 Factors that influence the rate of Melting or Freezing

42. Factor 1 - Temperature Remember the freezing/melting point of water is 0°C or 32°F. The higher the temperature the faster water will melt. The lower the temperature the faster water will freeze.

43. Factor 2 - Size and Shape If you have two equal masses of ice – one in a solid block and the other in smaller pieces - the smaller pieces will melt faster.

44. Factor 2 - Size and Shape (cont.) Just like with evaporation, the more surface area exposed to heat the faster water will melt. Likewise, the more surface area exposed to cold, the faster water will freeze.

45. In which cup will the ice melt quicker? A B

46. Factor 3 – Conduction Think about this. People control the temperature of food by placing it into styrofoam containers. Styrofoam is a poor conductor of heat. A styrofoam container will not change temperature quickly. This is why when you buy a cup of hot chocolate, it will probably come in a styrofoam cup. Your hot chocolate will stay warm longer and your hand will not get burned.

47. Heat Transfer If you place equal amounts of hot water into two containers - a metal container (a good conductor of heat) and a wooden container (a poor conductor of heat) - the water in the metal container would cool faster.

48. Cold Transfer Any time you place equal amounts of water at the same temperature into two containers – one a good conductor of heat and one a poor conductor of heat. The container made from a good conductor of heat will speed up the cooling of the water by conduction.

49. In which cup could you freeze 6 ounces of water the fastest?

50. Factor 4 – Changing the Composition During the cold and icy winter, you have probably experienced salt on sidewalks and roads. It is used to melt the ice and snow and keep it from refreezing. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving.