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Postby Proud Mom » Mon Mar 05, 2012 1:32 pm

I need help simplifiyng the reasons why a bubble stays together. My 2nd grader chose Bubble-Ology as her Science Fair Project, due this Thursday, 3/8/12. We experimented with all of the ingredients suggested on your site. There were 3 solutions we used to create bubbles. We then timed how long each bubble lasted (created approx. 20 bubbles and timed each one). Solution of water, Dawn, glycerin, light corn syrup were our ingredients per your chart. For a variation, we took all of these ingredients, added Elmer's glue and timed these bubbles. We increased the glue, and are going to time these bubbles this afternoon.

I've read Wikipedia's explanation about "Stability of soap films", Exploratorium's site about "Soap" and "Sticky Water", Bubbles.org's site about "Why do bubbles pop?", "bubble solutions" and About.com "Chemistry, Bubble Science". I need help simplifying this project so that my 2nd grader can understand and explain the following:

1. What makes bubbles stay together?
2. What solutions make an ultimate, long-lasting bubble (using home ingredients)?

Appreciate any help you can provide,

Proud Mom
Proud Mom
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Re: Bubble-Ology

Postby kgudger » Mon Mar 05, 2012 4:38 pm

Hello and Welcome to the Forums!

I'm not smarter than the Exploratorium, but I can see why a discussion of Hydrogen bonds might be above a 2nd grader. You might try explaining that water is made up of molecules that like to stick together. While not a magnetic attraction, it is a "polar" attraction and you can use magnets as a model of how the molecules stick together. As you read, soap reduces the pull on the water molecules (by getting between them). Pure water has too much pull, so bubbles can't form. Put too much soap in water and bubbles can't form, either. You could expand the experiment to show that there is a "best" amount of soap to add to the water to get good bubbles.

I don't know the ultimate bubble solution, but from practical experience I think the Bubble-Ology experiment demonstrates about the best you can get with home ingredients.

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Re: Bubble-Ology

Postby rmarz » Mon Mar 05, 2012 4:57 pm

Proud Mom - Soap bubbles are probably a little off our 'expertise' and experience, but it is a fun topic. As a grandfather, I'm also looking for the perfect bubble solution, and the conventional recipes of liquid soap detergent, glycerin, corn syrup and water seems to be most often cited. I'm interested in your results with Elmer's glue. But, back to your question. You have researched the 'what makes a bubble' so you have an understanding of surface tension, the addition of soap and other ingredients that become surfactants and allow the liquid to become a partially stable film. Fundamentally, the bubble breaks for two reasons. One, it contacts another surface. It breaks. The second reason is the one you are experimenting for. Evaporation.

As you can appreciate, the thickness of this soap bubble film is is very slight, in the order of a few microns (one millionth of a meter) down to several hundred nanometers (one billionth of a meter). The bubble material is a sandwich made up of soap molecules on the inner and outer surface, sandwiching water molecules in between. The bubble breaks primarily because of evaporation of the water. This film is somewhat porous, and water molecules are able to evaporate into the atmosphere causing a break in the film, and an escape of the air inside the bubble. The air inside the bubble, just before it breaks is at a slightly higher pressure than the atmosphere that surrounds it. When that pressure exceeds the films ability to maintain its structural integrity, the bubble breaks. This is the same as would happen if you overinflated a rubber or latex based balloon and exceeded it's structural strength.

I've attached a link to a website that might help as well. You can search for other references under "soap bubble thickness", "soap bubble colors" etc. Publish your best recipe findings. As a control, I would not make the bubbles too large, as that would be detrimental to your tests. Size is a variable that should be controlled unless you want to extend the experiment and use a constant solution and determine how size affects your result.

Rick Marz

http://www.ehow.com/facts_4966287_what- ... s-pop.html
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