This activity is a lot of fun for 6th graders to discover for themselves the relationship between diameter and circumference.

Given a small container of bubble solution, the student pours a little of it onto his/her desk and use a straw to blow a bubble. When a bubble pops, it leaves enough of an imprint on the desk for the student to measure its diameter and circumference with a string. Students continue to blow different-sized bubbles and record their measurements.

Mix these three ingredients together well for a perfect bubble solution. I doubled this recipe to make enough for 34 students working in pairs.

- 1 cup distilled water
- 2 tbsp Karo light corn syrup
- 4 tbsp Dawn dishwashing liquid

I put the bubble solution in small plastic cups. **Paper cups do not work!** I give students embroidery threads to use as “string” to measure diameter and circumference. Of course they then have to measure the string against a ruler to get a reading in centimeters.

They work in pairs — one person blows a bubble and measures, the other person records; they wipe off desk, string, and ruler after each bubble. Switch roles. I ask for at least five different-sized bubbles.

Not wanting to waste the leftover bubble solution, I let the kids go outside to blow bubbles in the Friday afternoon sun. One kid said, “Today is such a good day.” Other kids quickly chimed in to agree.

I really think they will remember that the circumference is about three times the diameter. Yeah, that 3.14159 pi thingy.

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[…] Fawn Nguyen’s students have fun investigating the relationship between a circle’s diameter and circumference in Friday Bubbles. […]