How do blowing bubbles work

What happens if you blow through a straw into a cup of soapy water? The bubbles last much longer. Often, there are so many bubbles that they overflow the cup. Another way to blow bubbles is with a bubble wand. These bubbles have a different shape to bubbles blown into liquids. Have you noticed that this type of bubble, whether big or small, is always round? Imagine a glass of water is sitting on your desk. Unless someone bumps it, the water looks perfectly still.

But if you could see the individual water molecules you would see something very different. Water molecules are in constant motion. The molecules touch each other, but they easily roll and slide past one another. Follow the recipe at the end of this article to make some super strong bubbles for your act. Wearing a clown suit is optional. A bubble is just air wrapped in soap film. Soap film is made from soap and water or other liquid. The outside and inside surfaces of a bubble consist of soap molecules.

A thin layer of water lies between the two layers of soap molecules, sort of like a water sandwich with soap molecules for bread.

They work together to hold air inside. Create a bubble that stretches out using a large wand that you can make from a piece of wire. Whoosh it through the air so that the bubble follows and grows behind it. Then, with great drama, let the bubble go. Give the students a chance to note what happens to it before it pops.

Why is a bubble round? Bubbles can stretch and become all kinds of crazy looking shapes. But if you seal a bubble by flipping it off your wand, the tension in the bubble skin shrinks to the smallest possible shape for the volume of air it contains.

Compared to any other shape, a sphere has the smallest surface area for the amount of volume. Blow several bubbles and have the students blow and fan them to keep them from landing. The object here is to watch them pop without obvious interference.

At low gas jet speeds, only a small dimple appeared in the soap film. The phenomenon, the researchers found, can be explained as a contest between the pressure the gas jet exerts on the film and the surface tension of the film, which resists any increase in curvature. At that point, the film has reached its maximum curvature, and the bubble can fill with gas and float away.

The researchers found that wider jets, which produce larger bubbles, create them at lower gas speeds than narrower jets. Repeating the study with a simple bubble wand gave similar results, suggesting that the laboratory setup is a passable proxy for real-world bubble blowing. The thickness of the soap film had no effect on the gas speed at which bubbles formed. When people blow bubbles, the jet is formed at their lips—some distance away from the soap film—and it may be wider than the wand.

Their findings give a precise recipe or set of instructions for how to blow bubbles—and with it, related production processes. National Science Foundation supported the research in part.

Source: NYU. Search for:. Science Health Culture Environment.