Look for: All conditions saw an increase in humidity, e…

3.A Analyze evaporation investigation data for patterns to provide evidence that increased temperatures cause an increase in evaporation leading to more water vapor entering the atmosphere.

• All conditions saw an increase in humidity, even the dry soil conditions.
• Wet soil conditions had a greater humidity increase than dry soil conditions.
• Heated conditions had a greater humidity increase than non-heated conditions.
• Increasing humidity in the bottle is an indication of evaporation occurring, so a larger change in humidity indicates more evaporation occurred in the same period of time.

If students do not identify that the humidity increased in all bottles, ask students if we have any conditions in which humidity stayed exactly the same or decreased. If so, did anything unusual happen with temperature for that condition. Follow up specifically on the locations experiencing drought and what we can conclude about evaporation in these places - that it is still happening.

If students do not identify that the heated bottles had higher humidity level changes, ask what differences they see between the two conditions (heated versus unheated). Connect back to students’ ideas about what causes water to evaporate (adding energy) and what conditions had energy added to them.

You may need to support students in the transition from humidity level changes to evaporation to evaporation rate. The concept of ‘rate’ is a change in one measure with another measure. In this case, it’s a change in the quantity of water vapor in the air (humidity) over time (8 min). Ask your students, Which condition had the greatest change in humidity in the same time period? What can we say about how fast evaporation was happening in this condition compared to the other conditions?

Lead a whole group discussion about the results. Display slide J. Say, Let’s revisit our initial question and see if our data allows us to draw a conclusion.

Suggested prompts

Sample student responses

Our question was whether increased temperature affects evaporation. What can we conclude now with the data we have?

• The heated conditions had more evaporation.
• If it’s warmer, there is going to be more evaporation.
• [students bringing energy ideas] When we added energy using the hand warmers, the energy transferred into the system to the water and it evaporated.

What patterns did we notice that surprised us or that we weren’t expecting?

• We didn’t think there would be much evaporation in the dry soil, but there was.
• Water is evaporating more everywhere in the warmer temperatures, even in dry soil places.

If there are increased amounts of water vapor in the air, how does that affect our water system model?

It should add more water in the air, and we should see more evaporation everywhere.

How does what we did here relate to the droughts and floods we’re investigating?

It should increase the amount of precipitation, so shouldn’t everywhere be flooding?

• The floods might just be more intense.
• Maybe the dry areas get drier because they run out of water to evaporate.
• If clouds stay in the same place then deserts should be getting more rain too, which isn’t happening.
• Say, It seems like we have identified that it means that there might be more water vapor in the air, maybe more precipitation and flooding, but we aren’t sure exactly what’s happening with the drought places if there is evaporation but no precipitation.