Frozen versus Room Temperature Rubber Band Stretch
Name: Bari
Status: student
Grade: 6-8
Country: USA
Date: March 2009
Question:
How does freezing versus room temperature effect a rubber
band's elasticity? I did an experiment and the rubber band exposed
to freezing temperature stretched farther than the one at room
temperature. Why did this happen?
Replies:
Bari,
We need to know some specifics about your experiment.
What temperature did you use for "freezing temperature"? How did you "freeze"
the rubber band?
Did you try several different rubber bands to see if the effect that you observed
was not an artifact of the specific rubber band? Did you try reversing the situation
so that the previously room temperature rubber band was now the frozen one (and vice
versa)?
How did you make sure that the same amount of force was used to stretch the rubber
band?
Did you freeze the rubber band and attempted to stretch it while still in its frozen
state or did you allow it to warm up a bit before stretching it?
As you can see, there are many variables in your experiment that have to be addressed
before any proper explanation can be made. Give us more details and maybe we can answer
your question.
Greg (Roberto Gregorius
Did you really do this experiment at constant temperature? The Hooke's Law constant for a
rubber band should increase at lower, but constant, temperature. However, if your
conditions were such that the rubber band warmed slowly with time during the course
of the experiment. What you observed is what would happen. The experiment you are trying
is not easy. Beginning and ending at room temperature keeps the temperature more or less
constant. But starting at a reduced temperature makes for a stiffer 'spring' that loosens
as time (and therefore temperature) increases with time. What happens if you start with
a rubber band at about 40 C. and let it cool to room temperature?
Also be sure that the measurement is made at constant rubber band length. As you can see
meeting all these boundary conditions is not so easy.
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