Bubble Geometry
What makes bubbles round? Explore the shapes and angles bubbles create when they join together.
This activity may be Fiddly and Messy
What makes bubbles round? Explore the shapes and angles bubbles create when they join together.
This activity may be Fiddly and Messy
Activity video
What will I need?
1.
Gather your supplies using the list above
2.
Add the glycerine and the washing-up liquid to the warm water and stir the mixture slowly for a minute or two – this is to help the glycerine dissolve.
3.
Slide the protractor underneath the lid, and lightly coat the surface of the lid with bubble mix. Dip the straw into the bubble mixture, and slowly blow bubbles, one by one.
4.
Carefully move the lid over the protractor so you can measure the angles where the bubbles connect.
5.
To make a cubic frame, fold a pipe cleaner to give it three loops. Put one piece of straw on each loop. This is one corner of the cube.
6.
Make seven more pipe cleaner corner pieces, and attach more straw pieces to complete the cube. Attach the handle.
7.
Dip the frame fully into the solution. Gently pull it out and blow a bubble in the middle with a straw.
- Why do you think a free-floating bubble is always spherical?
- Can you make a bubble frame of a different 3D shape? What happens when you blow a bubble in the middle?
- Can you blow a bubble inside another bubble?
A soap bubble is simply a very thin sheet of soapy water called a soap film surrounding a volume of air. A force called surface tension pulls the soap film tight, so that it always has the minimum surface area possible. That is why a free-floating bubble always forms a sphere.
If two bubbles of the same size join, the surface between them will be perfectly flat. But if they are different sizes, that surface will bulge into the larger bubble, because the air pressure is greater inside the smaller bubble. Whenever two or more bubbles meet, the angle between the soap films will always be exactly 120 degrees.
The way bubbles connect is the same as how bees build honeycomb. In each case, the angle at which the lines meet is always 120 degrees. The resulting hexagon pattern is the most efficient way for the honeycomb to connect using the smallest surface area for the volume of the individual cells. This means the bees don’t make more wax than is necessary.
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