We started with this Krampf Experiment.
http://www.krampf.com/experiments/Science_Experiment56.html
We are a member of his group on yahoo groups and get an experiment per week.
http://www.krampf.com/news.html
Here is the directions and ingredients.
Robert Krampf's Experiment of the Week
Ice and String
Imagine that you are given a full glass of water with a couple of ice cubes
floating in it. You are given a string and told to pick up the ice cube with
the string, without touching the glass, or the ice, or the water with your
fingers. Could you do it? Of course you could, if you knew a little science
and had a little salt.
For this experiment, you will need:
a glass of water
a couple of ice cubes
2 feet of thread
salt
To pick up the ice cube, lay the end of the thread across the ice cube. You
may want to loop the thread a couple of times, to give it plenty of surface
area to stick to. Then sprinkle about 1/2 teaspoon of salt on top of the
thread and wait about a minute. Then lift up on the string. You will find
that the string has frozen to the ice.
What happened? Pure water freezes at 32 degrees F. Adding salt to water
lowers its freezing point, allowing it to remain a liquid when it is colder
than 32 degrees. The surface of the ice cube, where the ice is beginning to
melt, is just below 32 degrees, so the addition of salt causes it to become a
liquid again. To make the change from a solid to a liquid, the ice must absorb
heat from its surroundings. That chills the water around it to the point
where it will freeze, freezing the string to the piece of ice.
The same process is used in making homemade ice cream. The ice cream mix is
placed in a container which is surrounded by ice and salt. This lowers the
temperature of the water enough to freeze the ice cream. You can quickly
make some homemade ice cream by placing 1/2 cup of milk, 2 tablespoons of sugar,
and a 1/2 teaspoon of vanilla extract into a zipper sealed sandwich bag.
Seal the bag tightly and then place it into a larger plastic zipper sealed bag,
along with 3 cups of ice and about 1/2 cup of salt. Seal the larger bag and
start shaking and squishing it to make the ice cream freeze evenly. After
about 3-4 minutes, the ice cream should become about as firm as homemade ice
cream gets. Open the large bag and remove and rinse the smaller bag, so that no
salt gets into your ice cream. Now grab a spoon and enjoy!
Have a wonder-filled week.
To join the list on Yahoo Groups, send a blank e-mail to:
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And our pictures from this experiment, which the girls *loved*!
Here they are trying to pick up the ice with the string before the salt.
Salt...
And finally...
Then of course, the ice cream making. We didn't have big plastic baggies so we found some old peanut butter jars and some jars bigger than the PB ones and used those to shake it up and it worked really well too.
And Finally, the *sweet* rewards (which they loved, ate a few bites, and put away for later)
