Going, Going, Gone ! Goal • Rate of evaporation changes • Some of the variables that create these changes • Scientific method Key Questions • How can you make a wet handprint disappear? • How can the rate of evaporation be changed, if at all? Focus • Experiment with making a wet handprint on a paper towel disappear • Use the scientific method to test variables which may affect the rate of evaporation • Relate these variables to weather conditions Time Frame • Approximately 1 week Materials • • • • • • • Paper Towels Water Water Containers Stop Watch Hair Dryer Light Bulb Eye Dropper or other measurement device Background Knowledge • Introduction to the Water Cycle • Definition of Evaporation • Changing states of matter –Liquid to gas Anticipatory Set • “How can you make the wet handprint disappear?” • Show students your handprint on paper towel • Have students think about this silently while pass out worksheet • Instruct them to try this and time themselves • Guide a discussion Changing Variables • “How can the rate of evaporation be changed, if at all?” • Group class into pairs and give them the worksheet • After obtaining approval, based on safety, available materials, and variation from other groups proposals, students may start experiments Presentations • Give each group a file folder and have them make a presentation with worksheets and graphs • Each group will give an oral presentation Discussion Questions • Was your test fair? Controlled Variables • What different ways were used to try to change the rate of evaporation? • How do the ways we used to evaporate water relate to nature? Fans – Wind, Light Bulbs – Sun • Under what conditions on Earth would a lot of water evaporate? • If you were in a desert, how could you keep water from evaporating quickly? Weather Connections • Unequal heating of Earth, causes changes in evaporation rates • Warmer it is – the faster the water molecules move and evaporate • This causes an increase in humidity, or the amount of water in the air, and the formation of clouds Extensions • Journals: Make a list of local sources of evaporating water, both indoors and outdoors. Pass out final worksheet • Competition between teams of who can get the same amount of water evaporated the fastest. • What if we changed the kind of paper towel?