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Krampf #468 Foam
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KRA-@aol.com
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Oct 18, 2006 18:06 PDT
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Robert Krampf's Experiment of the Week
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This Week's Experiment - #468 Foam
Greetings from Ft. Lauderdale. Nancy and I are enjoying the South Florida
weather while I am doing energy and electricity shows for Florida Power and
Light. Nancy is adapting to "life on the road" and seems to be enjoying it
quite a bit. We have been doing quite a bit of bird watching and nature
photography, as well as enjoying the local food.
It has been far too long since I did an experiment with ice cream, so I
thought this week would be a good time to correct that. We are going to
investigate foam. For this, you will need:
a bottle of water
carbonated soda
ice cream
OK, to begin with, what is a foam? According to the Wikipedia, "a foam is a
substance that is formed by trapping many gas bubbles in a liquid or solid."
OK that should be easy enough. We just need a lot of bubbles. Pick up the
bottle of water. Be sure that the lid is on tightly and then give it a
good, hard shake. While you are shaking, you should be able to see that there
are quite a few bubbles of air in the water. Now, stop shaking the bottle.
Instantly, the bubbles disappear. Pure water is not good at keeping bubbles.
Its surface tension, that "stickiness" that we looked at last time, gets in
the way and causes the bubbles to collapse. What we need is something added
that can stabilize the surface of the bubbles. We could use soap, which does
a very good job of disrupting the surface tension and makes very good
bubbles, but soap does not taste very good.
Pour some soda into a glass. Now we have some foam! Dissolved substance
in the soda help to stabilize the bubbles, making them last longer. Still, af
ter sitting for a minute or so, most if not all the foam will be gone. If we
want the foam to hang around longer, we need to add some chemicals to make it
stronger, and I know just where to find them.
Add a scoop of ice cream to a glass and pour some soda over it. This time,
we get even more foam, and the foam lasts much longer. Ice cream is already
a foam, with as much as half of its volume made up of air bubbles. To keep
these bubbles in place as the ice cream freezes, they add proteins, such as
eggs and cream, which can both be whipped into a very nice foam. These proteins
make the bubbles in the ice cream stronger, letting the manufacturer add more
air. This makes the ice cream lighter in texture. It also makes the end
product cheaper to make, since as much as half of what they are selling you is
air.
As you pour the soda over the ice cream, some of the proteins mix with the
soda, making the foam last much longer. How much longer? I don't know. I
always find myself eating the experiment before I can find out.
Have a wonder filled week.
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Robert Krampf's on-the-road schedule:
My calendar is now on-line. You can see a detailed calendar, with dates,
times, schools, etc. at http://www.krampf.com/m_tour.html
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From Robert Krampf's Science Education Company
PO Box 60982
Jacksonville, FL 32236-0982
904-388-6381
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