In learning environments that encourage students to ask questions, any teacher's knowledge may be challenged. In the water cycle exploration teachers discovered that they needed to dig deeper into their own understanding of evaporation. This page presents a group of fifth grade teachers grappling with evaporation. Its purpose is to serve as an example of the engagement that scientific practice requires for all science learners.

You may want to watch the videos several times to appreciate the teachers' conversation. You may also want to print the transcripts for taking notes and for reference later. When discussing the transcripts, cite specific line numbers to provide evidence or reference for your comments.
 

Evaporation: starting the discussion
As the video below opens, Jen pours a small puddle of water onto a plate and the group begins discussing its eventual evaporation.

Video 1

Examining the video. What are some characteristics of the questions being asked? What are your answers to some of the questions posed?
 

Surface area model
In the following video, Donna proposes a model for evaporation based on some reading she found in an Internet search. Donna admitted that it left her with new questions. Prior to this video segment, she stated:

… So what I'm learning is steam when you boil it, you can see it, I haven't been thinking about this much. And when stuff sits and just evaporates, you don't necessarily see it. Some people are saying that actually it doesn't have to boil, that water can just change into a gas without having to boil. That it can just change into a gas at different temperatures, I'm hearing that. So I'm wondering, and I saw some stuff about this on Google which I could not wrap my mind about. …

Video 2

Examining the video. What is the model for evaporation that the teachers have put together by the end of this segment? What questions do you have about their model?
 

Applying their model to new situations
In the next video, the group tries to apply their evaporation model to a some new contexts.

Video 3

Examining the video. Jen tries to apply the group's evaporation model to water boiling in a pan. Does this effort strengthen, weaken, or have no impact on the model? Next the group considers the model relative to what they know about the behavior of a lake when the weather is cold. What is the outcome of this effort? How does this discussion mimic the practice of science?
 

Proposing an experiment to test their evaporation model
In this video, Chris asks a question that turned into an opportunity for an experiment that could test the group's evaporation model.

Video 4

Examining the video. Testing a model is an important scientific practice. In our experience it is also a natural practice. The teachers here immediately recognized the opportunity for an experiment to test their model's predictions, and we find that students spontaneously seize the opportunity as well. What are some other experiments that could test the teachers' model? What would the model predict as the outcome for each experiment? Why is it useful to think about the model's prediction?
 

Being explicit about what causes evaporation
Just before this video segment, the group returned to a discussion of the sun and its role in evaporation. They mention among themselves that students always bring the sun into any discussion about evaporation. As this segment begins, David questions why the sun is important.

Video 5

Examining the video. The group teases out two aspects of their evaporation model. One is a condition for evaporation, i.e., that a water molecule must be near the surface of the puddle in order to be released from the puddle. The other aspect that the group teases out is that the molecule needs to have enough energy to leave the puddle, and this energy can be heat energy from the sun. David talks about a tangible reason for evaporation. What does he mean by tangible? How does this discussion relate to mechanism, or cause and effect?