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WHAT IS EVAPORATION? Design tests to find out how each of the following factors affects the rate at which water evaporates: 1) temperature: Does hot water evaporate faster than cold water? When we wash dishes and leave them in a drainer for Mother Nature to dry them, is there a difference if we rinse in cold water as opposed to hot water? 2) movement of the air: If there is a fan blowing across the liquid, what effect will the moving air have on the evaporation rate? 3) kind of liquid: Does cooking oil evaporate slower or faster than water? How about rubbing alcohol? 4) amount of moisture in the air (humidity): On a high humidity day, would evaporation of water be slower or faster? Prepare at least two conditions for each test, so that results can be compared. For example, to test the effect of air movement, place some liquid in front of an electric fan and an equal amount in another place where there is no wind but the temperature and humidity are the same. Observe saucers filled with water over a period of several days. Keep a daily record of what happens to the water. Fill a flower pot with soil, and pour water into the soil until it begins to drip from the bottom. Weigh the pot, then do not water it again for a week. After a week, weigh the pot again. Compare the before and after weights of the pot. What caused the difference? Pour 1/2 cup of water into each of two identical shallow pans. Place one pan in a warm location and the other in a cool place away from any breeze. Compare the time required for the water to evaporate from each pan. Make some judgment about the relationship of heat to evaporation. The test can be repeated and speeded up by placing the experimental pan over a heat source such as a hot plate or radiator. Similarly, two cloths of the same size and the same material can be substituted for the pans. Soak each cloth thoroughly in water. Set one cloth in a cool location and the other in a warm location. An analogy can be made to clothes on a clothesline on a sunny day and on a cloudy day. In each of the above tests, be sure that the heat factor is the only influence. ---o0o--- Pour one cup of water into a wide, shallow dish and another cup of water into a tall, narrow jar. Place both in direct sunlight. You will see that the water in the dish with the wide mouth evaporates faster than the water in the jar. Discuss differences in evaporation from small puddles and large lakes. Does ocean water evaporate? Where does liquid go after it evaporates?  Any problems with this page? Send URL to
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