Melting Ice Experiment #442
Grade Level(s): 1-2, 3-5, 6-8
Submitted by: Robert Krampf
This week's experiment comes from my favorite television program. I
don't watch a lot of TV, but I always make an effort to watch Good
Eats with Alton Brown. If you get the Food Network, the science in
this show is incredible. I highly recommend it to anyone who likes
science and food. When Mr. Brown performed this experiment, I
knew that I had to try it for myself. I thought that you might like it too.
You will need:
a pot of boiling water
your kitchen sink
Lets begin with a question. Which will melt an ice cube faster, cold
water or boiling water? At first, it seems obvious that the boiling water
would melt the ice faster, but then you probably thought that would be
too obvious, so it must be a trick question. Then you began trying to
think of a way that cold water could melt it faster. Well, you were on
the right track.
Start with a pot of boiling water on the stove. Then turn on the cold
water faucet in your sink. Select two ice cubes that are the same size.
Put one of them into the boiling water. Hold the other in your hand
and place it in the stream of cold water from the faucet. Watch to see
which melts first.
The ice cube in the stream of water melts first. How could cold water
melt the ice faster than hot water?
Ice melts as heat moves inward from the surrounding area. The
greater the difference between the temperatures of the ice and its
surroundings, the faster the heat will move inwards. So why didn't the
ice in the boiling water melt first?
When you first put the ice into the hot water, heat moved quickly in
from the surrounding water, causing the ice to melt. That left it
surrounded by a layer of cold water from the freshly melted ice and
water that had given up a lot of its heat as the ice melted. This layer
of cool water insulated the ice, slowing the melting process.
Even though the running water was cool, it was still quite a bit warmer
than the ice. It was flowing, so any melted ice was quickly carried
away, and the insulating layer of cold water did not form. The flowing
water provided a constant supply of heat to continue the melting
process, so it melted the ice much faster.
From Robert Krampf's Science Education Company
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