Puddles that evaporate.
This works fast in dry windy weather and even works on cloudy days if the temperature is above 70º F. You'll have to start over if it rains.
Objectives: Students first predict and later conclude in writing. Students collect data by using measurement. Students describe a simple example of replicable evidence and fact.
Materials:
Procedure:
Pour equal amounts of water on the concrete or asphalt forming two big puddles or a puddle for each group. Trace a line around the perimeter of the puddles with chalk. Keep the chalk line on the dry side since it will be harder to see later if marked on wet concrete. The students measure across the puddles and write this distance in their journals. Return to the area each hour or so and have the students measure across the wet area again. You can draw new lines around the remaining puddles. Each time the newest line will be inside the others until all the water has evaporated, usually within a few hours even when starting with a few cups of water.
Close:
In this demonstration there is not an important difference between the puddles. Having a puddle for each group helps confirm how water evaporates.
Do this lesson in combination with other water vapor and weather lessons.
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