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Chocolate Milk Bubbles Experiment #443
Grade Level(s): 1-2, 3-5, 6-8
By: Robert Krampf

This week's experiment is in honor of The Bubble Room, my favorite restaurant in this part of the state. If you have never been there, the place is sort of Willie Wonka combined with a flea market. Great food and lots of personality. It is called The Bubble Room because they have LOTS of bubble lights, the kind that you see as Christmas decorations. With all of those bubbles, I thought I would do a bubble experiment.


To try this, you will need:

a clear glass
some milk (It does not have to be chocolate, but I that is what I was in the mood for.)
a drinking straw


Pour yourself about half a glass of milk. Put the straw in the milk and blow gently through it. As the glass begins to fill with bubbles, notice how they connect with each other.

The first thing you will notice is that they join in three's. You will not find a place on the glass where the sides of four bubbles come together at the same point. Everyplace where the sides of the bubbles come together, you will see that there are three sides connecting.

The next thing is that the three sides will all be connected at the same angle. If you have a protractor (device for measuring angles), you will see that all of the angles are exactly 120 degrees, even if the bubbles are different sizes.

Why does it happen that way? Lets start with why bubbles are round. You get a bubble when a gas is trapped inside a liquid or solid. These bubbles are surrounded by a thin layer of milk. The air is pushing outwards in all directions, and the air outside is pushing inwards. This causes the air to shape itself into the smallest, most compact space, which for a single bubble is a round ball. With two bubbles, the most compact shape is to have a flat wall on the side where they come together. For three bubbles, the most compact shape is for them to meet at 120 degree angles. No matter how many bubbles you look at, the angles will always be the same.

To get a better idea of how this works, place several chocolate chip cookies on the table. No, technically they do not have to be chocolate chip, but I am in a chocolate mood. Of course, I am almost always in a chocolate mood. Put one cookie in the middle and then place the other cookies around it, fitting them as close together as you can. When you have the cookies arranged, look at the places where they come together. At each junction, there are....three cookies, just as there were three bubbles at each junction. Imagine that the cookies were soft enough to flow a bit. If they flowed into each other, what angles do you think they would form? 120 degrees, just like the bubbles. It is the most efficient arrangement.

If this arrangement is so efficient, you would expect to see it in other places, besides just the bubbles in a glass of milk. Take a look at a honey comb. After looking at the bubbles, the pattern you see will be very familiar. So with the angles.

Now, the last thing that we have to do is clean up. I wonder what we could do with a hand full of cookies and a slightly used glass of chocolate milk? Well, I am sure you will think of something.

From Robert Krampf's Science Education Company

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