Eyeing an Icicle
Today's Snack: Make mini-popsicles
in the freezer! Take an empty ice-cube tray and fill it with your favorite
flavor of juice. Put one or two pieces of fruit into each little compartment.
Grapes and cherries work great! Stick a wooden toothpick into each piece of
fruit so that it sticks straight up, or at least out of the compartment.
Freeze. It takes about an hour to freeze solid.
Measuring tape, yardstick or ruler
Glass measuring cup
When icicles form and hang
down from the rooflines, they often look smaller than they really are. Next
time you have a chance, if you live in a colder climate, be sure to have a
grownup help you get a ladder or stepstool ready, and then when you see
icicles, run outside and break one off.
Rush inside with it and measure its
length in inches. Write down your measurement. You can wrap a cloth measuring
tape around it at its thickest point, too, if you want to record its
circumference - how many inches around it is.
Now place it inside a
measuring cup, and weigh the cup containing the icicle. Record that weight.
Also, write down your guess: which weighs more, ice or water? We're going to
find out by purposely melting our icicle.
But first, estimate how much water
there is, frozen in your icicle. Is it one tablespoon? One cup? One gallon?
Write down your estimate.
Also estimate how much
that water weighs. Record your estimate.
When you're ready to
start melting your icicle, keep it in the glass measuring cup so that it sticks
straight up. You might have to prop it up.
While it's melting,
let's talk about icicles. They're spikes of ice that have formed when water is
dripping from above, hits air temperatures below freezing, and the water
re-freezes into ice. The most spectacular icicles are "ice columns," which are
icicles that are so long that they touch the ground.
The good news about icicles is
that they're pretty. The bad news is, they can signal that there is too much
heated air escaping from the interior of a building. There should be more
insulation added, most likely, when you see rows of long icicles on a house or
Worse, icicles are heavier than
you think, and if they get too long and break off, they can do serious damage
to anyone or anything that's below them. They also can literally tear off the
overhangs, eaves or gutters that they are hanging from. And when icicles hang
from tree branches, as we've seen all over the country in bad ice storms, if
the icicles get too heavy, they can break off tree branches - even very large
When your icicle is totally
melted, get out your estimates, and get ready to see how you did.
First, how close did your estimate
come to how much water is in the measuring cup? Did you think it would melt
down into a lot more water than it did? Are you surprised, since your icicle
seemed to be so long? Or did it create less water than you expected?
Second, weigh the measuring cup on
the scale, and then pour out the water and weigh it again. Subtract the
difference, and that will tell you how much the water that formed your icicle
weighed. How close did your estimate of the weight of that water come to the
actual figure you recorded, of the weight of the icicle?
Also, did you guess that the
icicle would weigh more, or the melted water? They should weigh the same,
because ice and water weigh the same. This exercise should teach you that
molecules are molecules - even though the icicle seemed heavier because it was
so long, its weight is exactly the same as the amount of water it melted down
into. The melting process does not make it heavier or lighter.
Here's one more exercise:
Can you figure out how much water
per inch of your icicle there was? For example, there are 8 ounces in a cup. If
your icicle was 16 inches tall, and melted down into one-half of a cup of
water, that's 4 ounces of water. If you divide 4 ounces by 16 inches, you get
.25. That means that every inch of that icicle melted down into one-fourth of
an ounce of water.
It has a lot to do with
the circumference of your icicle. Remember, that's a term for how big around
your icicle is. Do you think thick icicles use more water per inch, or less?
Go ahead and guess how much water
per inch your icicle melted down into. Then, using your records of how many inches
long it was, and how much water it melted down into, figure it.
If you got it right, or
pretty close, congratulations. You not only ACED it - you ICED it!