Have you ever placed a can of cola in the freezer, hoping to
make it get colder faster? Great, but I hope you didn't leave
it there overnight. If you did, the next morning you would
have found a can that had exploded, with shards of cola slush
all over the freezer.
No, cola doesn't contain TNT. In fact, the phenomenon is
caused by a healthy ingredient -- water! The same property of
water that caused the cola explosion also causes ice cubes to
float.
QUESTION: What is this property of water that causes the two
observations described above?
ANSWER: Because of its special chemical structure, water
expands when it freezes. Other compounds, like alcohol,
contract as they freeze. A can of cola has just enough room
for the cola, but if the cola freezes to take up more space,
it will force the can to break open. Ice cubes float because
ice is less dense than water, meaning that it has fewer
particles in the same area.
We can see that Hashem has our safety and welfare in mind
from the way that He designed water. Much of the water on
Earth is stored in the form of icebergs which float at the
surface of oceans in cold climates, near the North and South
poles.
If the opposite were true, this ice would sink and rest at
the bottom of the ocean. As a result, the ocean waters would
creep up and cover much more land than they do now,
eliminating many of our favorite cities! The fact that Hashem
makes water expand when it freezes allows people space to
live. [It also enables the fish to survive in winter, but
that's another lesson...]
Try this: To see whether water expands or contracts
when frozen, fill a measuring cup with water to the volume of
your choice. Place it on the table and look at eye level to
make sure the water goes exactly up to the line you chose.
Place the measuring cup in the freezer on a flat shelf for
several hours, until the water is completely frozen. See if
the volume has changed.
An easy way to simulate what would happen if an iceberg
rested beneath the ocean is to place an ice cube in a cup and
fill the cup to the very top with water. Carefully push the
ice cube down with a fork, just until the whole ice cube is
submersed.
(Avoid immersing the fork itself into the water because then
it will take up space in the cup.) The water that flows over
the sides of the cup represents the ocean water that would
come up onto the land.
