Interestingly enough, students who believed that the can
would expand were just as likely to blindly apply the gas laws
as those who thought it would collapse:
The gas molecules are moving around very quickly and
bouncing off the sides of the can quickly, causing expansion.
They are moving quickly due to the temperature
and because as temperature increases, so does volume.
(Spring 1997)
The water vapor inside it would continue to press out
against the can due to Charles Law, and the can would
possibly explode if the pressure was large enough.
(Spring 1997)
In total, 23 of the 70 control students quoted gas laws in
their responses.
A more alarming student response was also identified
from two control students’ responses: they expressed the belief
that the molecules themselves are capable of changing their
size and shape.
The gas molecules when heated are expanded and when
they cool they “shrink” back not taking up as much space
as before. (Spring 1997)
The gas molecules take the shape and volume of the
container they are in. They would be moving around
quickly because of the heat, and would create pressure
to get more space. (Spring 1997)
Other students wrote comments that seem to suggest
that energy behaves like a form of matter on the macroscopic
level—that it could be trapped in a sealed container:
Since the molecules were taken off the heat, they would
be moving slower than before. They would also be colliding
with each other less. But since it was capped, there
would be no place for the excess energy to go and the
can would get bigger. (Spring 1997)
With some responses, it was not so much what the students
wrote but what they failed to write. Several students did
not mention the changes in pressure or volume or the role of
the liquid in any way, while others were very vague about
how these changes in pressure or volume actually occurred: