This Week's Experiment - #469 More Foam...and Less

This week's experiment comes from Kaitlin, Cody and Jenna Russell. They wrote to tell me that they made a very interesting discovery about how the order that you add ingredients makes a big difference. To try this, you will need:

carbonated soda
ice cream
two glasses

Lets start by recreating their experiment. Does it make a difference which ingredient you add first? Put a scoop of ice cream into one glass. Pour some carbonated soda into the other. Now, lets compare the difference. Add some soda to the glass with the ice cream. Try to add the same amount of soda that you put into the other glass. Watch carefully, to see what happens and how much foam you get.

Next, add a scoop of ice cream to the glass with the soda. Again, watch carefully. This glass has quite a bit less foam. Why?

In the glass where you added the soda first, the soda produced foam all by itself. If you watched carefully, all this foam vanished when you added the ice cream. Even a tiny bit of ice cream added to the soda will cause all the foam to go away. The proteins from the ice cream change the surface tension, so they actually destabilize the old bubbles as they stabilize the new ones. Part of our foam is going away as the rest is forming.

Adding the ice cream causes the carbonation to leave the soda very quickly. Once you have some ice cream mixed in with the soda, you will notice that it is totally "flat," with no carbonation left. If part of that carbonation has already come out before the ice cream was added, there will be less gas left to form bubbles, so you will get less foam. If you totaled all the bubbles, both before and after the ice cream, you would get the same amount as if you had added the ice cream first. Now that you know what to watch for, you will probably want to do the experiment again, after you finish eating the first one.

Have a wonder filled week!