Condensation Concept Cartoon

This cartoon was developed to assess students' ability to:

• Explain the phenomenon called condensation. Condensation occurs when water vapor (water particles too small and spread out to see and always in motion) in the air comes in contact with a cool surface, slowing the motion of the particles enough to allow them to gather together and form water drops on the cool surface.

This cartoon is typically used after Investigation 9, Why do the water drops form?

Things to look for in student responses

Do students realize that (a) the source of condensation on the outside of glass is water vapor in the surrounding air and that (b) for condensation to appear, water vapor must be cooled?

• Some students may agree with Leila that water has seeped through invisible pores in the glass – this idea is commonly held by students. Students who don't agree with Leila may point out that water can't seep through the other glass because it is solid and offer another explanation.
• Others may agree with Fern and explain that the drops are only on the outside of the cold glass of water, that there are tiny particles of water in the air called water vapor, and that when water vapor comes in contact with a cool surface, the particles slow down enough so they can gather together to form drops.
• Still others, who hang onto the idea that the source of droplets is water in the glass, may erroneously agree with Deneb. Students who disagree may point out that there are no droplets near the top of the cold glass which you might expect if the water was moving from inside the glass, over the rim, to outside and offer another explanation.