This Week's Experiment - #244 Ice Race
I got the idea for this week's experiment Saturday while I was at the Miami
Museum of Science. In between my shows, some students were doing cooking
demonstrations. They were cooking mushrooms (Which were delicious!) and
talking about fungi. Watching them chop the mushrooms started me thinking
and soon I had this week's experiment. You will need:
a wide, plastic container
a plastic cup
water
a freezer
Fill the plastic cup with water and pour it into the plastic container. Then
fill the cup again. Place the container and the cup into the freezer. We
are going to wait until the water is frozen. While you are waiting, make a
guess about which you think will freeze first. Wait a minute! They both
have the same amount of water, don't they? Doesn't that mean that they will
both freeze at the same rate? Take a quick peek every 15 minutes until one
of them is completely frozen. Which one froze first?
The water in the wide container froze much faster. Why? Even though they
both have the same amount of water, they are in very different shapes. The
water in the wide container is much more spread out. It has a much larger
surface. The surface is where the heat is transferred, so the more surface
area, the faster the heat will be transferred and the faster the water will
freeze.
You can see the same thing in reverse. Let the cup and the wide container
stay in the freezer overnight, to be sure they are both well frozen. Remove
them and place them on the table. Wait and check them periodically, to see
which one melts first. Which do you think it will be? Right! The wide
container melts faster, again because it has more surface area.
What does all of this have to do with cooking? Think about cooking potatoes.
Imagine if we had a pot of boiling water and two potatoes. If we put one
potato in whole and cut the other into one inch cubes, which would cook
faster? The cubes, right? Cutting the potato into pieces means more surface
area, which means it cooks faster. That is why we often chop vegetables
before we cook them. It lets them cook faster and more evenly. I have
always enjoyed cooking and it is even more fun when you can see the science
in it.
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
krampf@aol.com
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