Evaporation Concept Cartoon

This cartoon was developed to assess students' ability to:

• Explain the phenomenon called evaporation. During evaporation, water changes from the liquid to the vapor phase. Children have many experiences with evaporation in their everyday lives. However, explaining what has happened to the water is particularly challenging when they know very little about gases and how they behave.

This cartoon is typically used after Investigation 7, What happened to the water?

Things to look for in student responses

Do students realize that the water from the puddle is now in the form of water vapor, a gas that is part of air?

• Some students may agree with Fern that the water in the puddle is made of particles that have escaped from the puddle, moved apart, and are now spread out in the air. The particles in water vapor are too small and too spread out to see.
• Others may agree with Deneb and think that it has "gone," meaning it is no longer water, it is not part of air, and the water in the puddle is not matter that is conserved. Those who disagree with this idea may point out that the water from the puddle still exists only it's water vapor which is invisible.
• Students may agree with Tomas that water from the puddle is in the clouds. While there may be some truth to Tomas's idea, as some water particles from the puddle may make their way to a cloud, students preference for this idea over Fern's may be a sign that they think water vapor is visible. Students may point out to Tomas that some or even most of the water from the puddle will become invisible water vapor in the air.