This Week's Experiment - #215 Melting Icebergs
This week's experiment comes from a report I recently heard on National
Public Radio. Unfortunately, I was driving and could not write down the
fellow's name, so I could give him proper credit. He was talking about the
facts and fictions of global warming. One point that he mentioned was one
that I had heard many times and had never thought all the way through. What
would happen if the global temperature rose enough for much of the polar ice
caps to melt? All of that extra water would cause worldwide flooding, right?
Lets investigate. You will need:
a glass
water
ice cubes
Try to get a large lump of several ice cubes frozen together. You can place
several ice cubes into a bowl and leave it in the freezer over night and they
should freeze together. Place the ice cubes into a glass or bowl. Add
enough water to fill the glass to the top. Add as much water as you can,
until the glass will not hold any more without overflowing.
Now, look carefully at the glass, water and ice. There is quite a bit of ice
sticking up above the glass. What will happen when the ice melts? Now that
you have formed a hypothesis (a scientific guess), watch to see what happens.
Be sure that the glass is not bumped or disturbed. As the ice melts, does
the water overflow?
No, it does not. Even when all of the ice has melted, the glass is just as
full as it was when you started. As water freezes, it expands. It still
weighs the same, but it takes up more space. This means that it will float
when you put it into water. As it floats, the part of the ice that is
underwater takes up exactly as much space as the water that it formed from
took up. When it melts, it will take up that amount of space again, and so
the glass does not overflow.
Back to what would happen if the polar ice caps melted, there is a big
difference between the two polar ice caps. The North polar ice is all ice,
floating in water. If you could selectively melt just the northern ice cap,
sea level would stay the same.
The southern polar ice cap is not floating. Instead, it sits on the
continent of Antarctica. If it melted, then the sea level would rise. The
fellow that was giving the information said that most of the figures for
global flooding overstated the rise in sea level because they failed to take
into account that the northern ice would not change sea level. I have not
been able to verify that, but I will keep my ears open. And of course,
global warming would also melt a lot of ice in other parts of the world, not
just the ice caps. Still, it does make a nice experiment of the week.
From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
krampf@aol.com
To start receiving the Experiment of the Week, just
send a blank E-mail to: krampf-subscribe@topica.com
|
