Lesson: Evaporation


The Water Cycle


  1. To demonstrate the concept of evaporation



Teacher wipes a damp sponge across the chalkboard. The class should watch and make observations about what happens. They should notice the streak slowly disappear. Ask:"Where does the water on the board go? What happens to puddles after it rains? Where does the water go? Have you ever seen clothes hung out on a line to dry in the sun and wind? Where does the water from the wet clothes go?"



The next day, have pairs observe their plates and puddles. Ask : "What happened to the water? Where did the water go? What is the name for water going from liquid into the air? (evaporation) What is the name for water that is in the air? (humidity) How do we measure the amount of water in the air? (humidity detector)" Review how the air acts like a sponge to soak up water. Like the sponge, the air can hold only so much water. Ask : " What kind of weather would you expect to happen if there was a lot of water in the air or high humidity? What kind of weather would you expect to happen if there was very little water in the air or low humidity? What kind of humidity values would you see on cloudy or foggy days? What kind of humidity would you expect to find on a clear and sunny day? How would you dress or prepare for school on a high humidity day?"

Vocabulary Words:


Discuss: When we left our plates with puddles out overnight and came back the next day, what did we find? What had happened to the water? Do you think the humidity in the room changed overnight? How? Why? Do you think the humidity outside changes when you hang your wet clothes outside to dry? Why?

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