All Resources

Catch a Bubble

In this demonstration students learn what causes bubbles to pop and what they can do to increase the longevity of their bubbles.

Why bubbles pop

The film of soapy water that forms the ‘skin’ of a bubble has a structure like a sandwich. Two layers of soap molecules (the “bread”) sandwich a “filling” of water. 

A bubble will stay a bubble as long as its water “filling” is trapped between the layers of soap. It will pop when that water is lost in some way. There are a few different ways that a bubble can lose its water and pop:

  • When you make bubbles in the sun, or in a place with very dry air, they evaporate quickly. 
  • In the wind, bubbles are much more difficult to create and will be popped by puffs of air. 
  • If a bubble touches a dry finger, it pops because the water molecules are attracted to your dry skin. 

Increasing bubble life expectancy

Here are some recommendations for the best conditions for making bubbles:

  • Avoid bright sunlight: play in shady areas, in the early morning, or just after sunset.
  • Avoid the wind: choose a calm day or a sheltered location.
  • Choose a damp day. Immediately after a rainstorm is ideal.
  • Move to where your bubbles don’t run into dry objects.
  • Add glycerine to the bubble solution to make your bubbles last longer. Glycerine is hydroscopic, which means that it attracts water, so the bubbles evaporate more slowly.
  • Keep your hands and bubble tools really wet with bubble solution.

Objectives

  • Use their knowledge of soap films and minimal surface structures to make bubbles of various sizes, shapes, and arrangements.

Materials

Key Questions

  • When does a bubble pop?
  • Why does a bubble pop when you touch it with dry hands?
  • Why does it pop when it hits the floor?
  • Why does the bubble not pop when you touch it with wet hands?
  • Would the bubble pop if you wet your hands with plain water instead of soapy water?

What To Do

Activity

  1. Select a volunteer from the class to catch as many bubbles as they can.
  2. Blow streams of bubbles using a small bubble wand for the student to catch. (Every time a bubble hits their hands it will pop).
  3. Discuss as a class why the bubbles pop every time the volunteer touches the bubble. What can our volunteer do to actually catch a bubble?
  4. Cover the volunteer’s hands in bubble solution and blow a small bubble above them so that it will float down into their hands.

Discussion

  1. Discuss some conditions that are bad for the stability of bubbles.
  2. What causes the bubble to pop in each of these conditions and what can you do to prolong the life of your bubbles?

Extensions

  • Can you devise a way to pierce a bubble with a straw or a pin without popping it? (Hint: dip the pin in soap!)

Other Resources

Exploratorium | Bubbles
Soap Bubbles | Soapbubble.dk