Kids of all ages, including adults, adore the sheer joy that soap bubbles bring. These delightful globes of soapy liquid are fascinating to watch as they float through the air, shimmering and changing color in the sunlight.
Kids love to create them, chase them, and try to catch them before they pop, which can provide endless hours of entertainment.
Bubble play is a timeless and classic game that has captivated generations of kids.
But have you ever wondered why bubbles pop when they’re touched?
The answer lies in the delicate structure of the bubble’s thin film. When the film is touched, even by the slightest amount of pressure, it ruptures, causing the bubble to burst.
Remarkably, however, there are ways to touch and even pierce a bubble without causing it to pop.
Let's do a simple soap bubble experiment to see how.
- dishwashing liquid
- glycerin (optional)
- a dish
- a straw
- adult supervision
- Mix 1 cup of water with 1 teaspoon of dishwashing liquid in bubble container.
- Add 1 teaspoon of glycerin and stir gently to make a bubble solution. (optional)
- Pour small amount of this bubble solution onto the dish.
- Put one end of the straw into the solution and blow. Make sure the entire opening of the straw is submerged into the solution to make a bubble form.
- After making a big awesome bubble, remove the straw slowly.
- Wet your finger completely using the remaining soap solution.
- Poke and to make bubble collapse!
- You should be able to poke through the bubble without popping it.
- If the bubble pops when you touch it, then your finger is not wet enough.
Understanding the Science Behind Bubbles
To comprehend why a wet finger doesn’t burst the bubble, let’s first consider the molecular structure of water.
Although beyond the reach of the naked eye, water is composed of innumerable tiny molecules.
Water is made up of tiny polar molecules that are attracted to each other, creating a force known as surface tension.
Surface tension is a result of cohesive forces between water molecules. It is a critical property of water that binds the molecules and causes water to form droplets. This same force is responsible for the dome shape when you overfill a drinking glass.
Consequently, a bubble forms, with its shape determined by the spherical stress distribution within the thin film.
A soap bubble’s film features a thin layer of water suspended between two layers of soap molecules.
Why Bubbles Pop
A bubble pops when the water trapped between soap layers evaporates, or the balance between forces is disrupted, and bubbles burst.
In everyday life, the familiar sight of bubbles piling up during a bath shows the principle that surface tension determines bubble form and behavior.
While surrounded by a soapy liquid environment, the bubbles’ flexible skin maintains its integrity, and they do not easily burst.
Why Bubbles in the Experiment Didn’t Pop
A simple soap bubble experiment can reveal more about bubble collapse and surface tension.
Using a soapy water mixture, glycerin, and a straw, one can create bubbles of various sizes and examine their characteristics under different conditions.
Wetting one’s finger with the soapy solution allows the bubble to be touched without popping.
Adding glycerin to homemade bubble solutions increases the longevity and size of bubbles by making the bubble film thicker and more viscous, preventing it from evaporating or thinning too quickly.
Viscous bubble bursts, therefore, are less frequent.