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Evaporation and Condensation; FOSS
 Lesson
at a Glance:
Curriculum: Full Option Science System (FOSS), Water
Module: Investigation 3, Water Vapor, Delta Education
Grades: Third and fourth
Topic: Evaporation and condensation
Prior to teaching Water Vapor, Linsey led her students through
a hot and cold water investigation, in which they compared the properties
of water in liquid and solid (ice) states.
Linsey introduced Investigation
Three by asking the students to recall a recent recess period during
which they observed that the ground outside
had become dry after a brief rain shower earlier in the day. In the discussion
that followed, their interpretations of what happened were clearly informed
by what they learned about the water cycle in second grade.
This led to
an experiment in which they took two paper towels and soaked them in
water, rung them out, and then put them in plastic cups on a
balance and made sure they were equal. They then covered one cup and
left the other
exposed to the air overnight to see what would happen the next day. “Some
of the kids predicted that it depended on where the balance was placed
in the room,” Linsey said, “and some thought that it depended
on whether we left the lights on all night. The ones who predicted
that the covered cup would drop realized that the paper towel in the
uncovered
cup was exposed to air.”
In a follow-up lesson, Linsey’s
students watched as water droplets condensed on the outside of a plastic
cup filled with cold water and then
tried to explain why the same phenomenon didn’t occur on a cup
filled with room-temperature water.
“
I would say that the big idea of both of these lessons is getting the students
to understand that water is in the air. Where does the water go? Well,
it’s everywhere. You know, getting them to understand that water
vapor is part of the cycle, that it is a gas, and that it can change back
into a liquid again. I’ve been teaching this unit for four years,
and every time I find that I really need to ask the students what they
know about things ahead of time, in order to help me to know where to go
as well.”
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