The Science of Soap Bubbles

How Are Soap Bubbles Formed?

Soap bubbles are created when we blow air into a soapy solution. They are pockets of soap and water filled with air. 

The soap forms a thin skin or wall and traps the air inside, creating a bubble. 

The outside and inside surfaces of a bubble consist of soap molecules. A thin layer of water lies between the two soap molecule layers, and the air is trapped inside like a sandwich.

A soap bubble lasts only as long as the water lasts.

When the water evaporates, the soap bubble’s skin gets thinner and thinner until it finally pops. 

Why Are Soap Bubbles Round

When we combine soap and water, their molecules mix and make a flat soap film. When you add volume by blowing air, it creates surface tension.

Surface tension is a force that causes liquids to stretch. 

Bubbles that float in the air and are not attached to anything are always round because the thin wall of soap pulls in while the air inside of it pushes out, forming a sphere.

A sphere, the round ball shape of a bubble, is the best way to take up little space and hold a lot of air. 

Why Are Soap Bubbles Colorful?

A soap bubble is like a little magical ball of rainbow. 

Light is the magic wand that causes the myriad colors we see in a soap bubble.

• Some light rays reflect off the outer surface of the soap bubble, while some enter the soap bubble and reflect off its inner surface.
• When we first blow a bubble, we see green and blue, then magenta or purple, and then just before the bubble pops, most of it will be a dark golden yellow color.
• As a bubble floats around, the colors change as the soap and water layers’ thickness and the overlapping light rays create specific color combinations

Fun Facts

Here are some interesting facts about soap bubbles:

• The largest recorded free-floating soap bubble was over 105 feet long!
• Studying bubbles helps scientists understand principles like surface tension, elasticity, and even how cells work.
• In very cold temperatures, bubbles can freeze! They form delicate ice crystals and can look like tiny snow globes.
• Soap bubbles date back to 3000 BC when the Sumerians produced soap for the first time.
• The largest soap bubble blown by hand is 0.25 m³ in volume.

Review

Let’s quickly recap what we learned about the science of soap bubbles:

• What are the three ingredients that make up a soap bubble? Soap Molecules, Water & Air
• What is the force that causes a liquid to stretch? Surface Tension
• What shape takes up the least amount of space and holds the most amount of air?  Sphere
• What causes the myriad colors we see in a soap bubble? Reflection of Light
• What happens to a bubble when the water evaporates? Pops