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Bubbles fascinate both children and adults with their beautiful shapes and colours. Such simple ingredients—soap and water—create mesmerizing examples of both geometry and chemistry. By experimenting with bubbles, students learn about surface tension, elasticity, minimal surface structures, and how to blow really, really big bubbles!
Making Bubble Solution
Catch a Bubble
Magic Bubble Wands
Body in a Bubble
Stick and String Bubble Wand
Zubrowski Bubble Wands
Paper Plate Bubble Wand
Bubbles are soap films wrapped around air. Soap films are made from soap and water. The soap film looks like a sandwich with soap as the bread on the outside and water as the filling on the inside.
Soap molecules have two ends, a hydrophobic end and a hydrophilic end. The hydrophobic end avoids water and attaches to oil. The hydrophilic end avoids oil and attaches to water. Soap thus helps attach oily dirt to water so the dirt can be washed away from clothes and dishes.
Surface Tension & Elasticity
Surface tension is the force between liquid molecules at the surface of the liquid (in this case water). The water molecules cling to each other, which causes the surface of the water to behave like an elastic sheet. Elastic substances tend to return to their original shape when they're stretched.
Water doesn't make stable, free-floating bubbles all by itself. If you blow a bubble in water, it pops quickly because the surface tension of the water is relatively high and the water is not very stretchy. Adding soap decreases the surface tension so that the water can stay stretched around the bubble.
Even as the bubble is blown up larger or is stretched in various ways, soap stabilizes bubbles by an action known as the Marangoni effect. In places where the bubble is stretched, the surface concentration of soap decreases, which causes the surface tension to increase. This area of increased surface tension springs back to its original form and prevents the bubbles from stretching to the point of popping. The result is spherical bubbles with a uniform surface tension.
Soap also reduces water evaporation so the bubbles last longer, although this effect is relatively small.
Minimal Surface Shapes
When you play with bubbles, you'll notice that they come in predictable shapes. That's because deforming a bubble takes energy. The bubble tends to spring back to the shape that is stretched as little as possible – the minimum surface. Floating around in the air, a bubble will become a sphere, because a sphere has the least surface area for a given volume of air. Another way to think about this is that the bubble is stretched most evenly as a sphere (as compared to an egg shape, or a cube). A shape with corners or edges means that the soap is stretched unevenly.
» Tips for Producing Giant Bubbles!
Big bubbles are fun for all ages. Follow these tips for the best results:
elasticity: The tendency of materials to return to their original shape after being deformed.
hydrophilic: Attracted to water.
hydrophobic: Repelled from water.
Marangoni effect: When liquid flows away from regions of low surface tension to regions of high surface tension.
minimal surface shape: A shape that has the least surface area for a given volume of air.
surface tension: The force between water molecules at the surface of the water.
» Exploratorium | Ron Hipschman | Soap bubbles
» Frederick Brasz | Soap films: statics and dynamics
» Weird Science Kids | Soap bubble
» Exploratorium | Ron Hipschman | Shape of bubbles
» Soapbubble.dk | The geometry of soap films and soap bubbles
» Einstein Online | Spotlights on relativity | From soap bubbles to Einstein
» The Groundwater Foundation | Fun with bubbles
» The ExperiMENTALS | Experiments | Make a cube-shaped bubble
» Steve Spangler Science | All about air | Square bubbles
» Bubblesphere | Questions about bubbles | Why are bubbles round
» Home Science Tools | Super soap bubble solution
» SFU Physics | Community outreach | Bubble tricks
» Balloon HQ | Soap bubble magic
» Steve Spangler Science | All about air | Giant bubble experiment
» eHow.com | How to put a kid in a bubble (with homemade, extra strength
» Bernie Zubrowski | Soap bubbles
» Come Together Kids | Really big bubble maker
» About.com | Bubble wands
» Creative Kids at Home | Activity library | Bubble wands
» Bubblesphere | Questions about bubbles | Why do bubbles have color?
» Wikipedia | Soap bubble
» San Diego Supercomputer Center | Bubble prints
» Yahoo! Voices | Kid craft recipes | Bubble paint recipes for making bubble prints
» Soap Bubbles | soapbubbledk
» David A. Katz | The Chemistry (and a little bit of physics) of Soap Bubbles
» Bubbles by Bernie Zubrowski, Little, Brown & Company, 1974. ISBN 0-316-98881-2-pbk.
» Soap Bubbles and the Forces that Mould Them by Charles Vernon Boys, Cornell University Library, 1890.