Bubble Science

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Blowing bubbles is a fun activity. Understanding why bubbles form, and why they are round takes science. The warm summer days are a perfect time to have fun learning about the science of soap and water. First, let’s think about why bubbles form. The bubble solution sold at toy stores and supermarkets is just a solution of soap and water. The solution is mostly water, but the soap is definitely required. You can’t blow a bubble using water (try it!).

So, the soap must be providing something important. To understand why large round bubbles form (and last) in a soap and water solution, but not in pure water, we must think about what is happening at the molecular level. Water molecules are attracted to each other very strongly (water has high surface tension) which means that they will not stretch apart to form large bubbles. Soap lowers the surface tension of water, allowing the bubbles to form.

How does soap lower the surface tension of water?

Soap molecules are long chains of atoms. One end of the chain is able to slip between the water molecules (scientists say that part of the soap molecule is hydrophilic), while the other end tends to stay outside of the water molecules (that part is hydrophobic). Because part of the soap molecule is able to push water molecules apart, soap lowers the surface tension of water and allows bubbles to form and last. Some bubble recipes contain more than just soap and water. Glycerin and corn syrup are frequently recommended. Why? Well, bubbles pop as the water in the film evaporates. Both glycerin and corn syrup can help prevent the evaporation.

After making the bubble solution, blow some bubbles. If a bubble wand (from commercial bubble solution) is not available, one can be made from a pipe cleaner. Try different shapes? Does a square wand make a square bubble? (NO—blown bubbles are always spherical,!) Try to see if you can stick something pointy right into the bubble—a pipe cleaner or toothpick works for this. (hint: wet it first). Try some experiments. Compare solutions with and without glycerin. Do the bubbles last longer (use a timer and collect data on many bubbles before reaching any conclusions). Does corn syrup work as well as glycerin? (Try this outside to avoid spraying bug attracting sweet droplets inside the house). Does glycerin make a difference? Does the brand of dish soap matter? Come up with other questions and test them out!

Make Your Own Bubble Solution and Bubbles!

Liquid dishwashing soap (Dawn or Joy are brands that are often recommended)

Glycerin (optional)

Water (distilled is recommended)

Bubble wands (can be made with pipe cleaners)

Container to hold solution

1. Measure one cup of water into the container.
2. Add 2 tablespoons of detergent.
3. Add 1 tablespoon of glycerin (optional)
4. Mix gently
5. Make bubbles!