Why do bath bubbles pop when I sprinkle talcum powder on them?

croc attack!!! by Nizam Uddin, on FlickrFor most of us, kid’s birthday parties are a nightmare that are best avoided. Having to supervise one would be an experience with few perks. One of which would be getting to eat chocolate cake. Another would be getting to blow party bubbles. Because, let’s be honest, you never get too old for playing with bubbles.

Yet despite their instant fun factor, soap bubbles never last very long and pop disappointingly quickly. Up close, each bubble is a small, air-filled balloon with delicate walls made of a soap and water mix. With a surface thinner than a human hair, the bubble wall is so fragile that a tiny particle of dust can be enough to pierce it. Sprinkling talcum powder on bath bubbles, for example, is like showering a layer of balloons with pins.

But bath bubbles would never be there were it not for the soap – it is extremely difficult to make bubbles in pure water. Water has surface tension – a tendency to want to stay together in blobs and drops. Without soap, each time you make a plain water bubble, the water will pull itself together causing it to quickly collapse. With soapy water though, the soap molecules get in between the water molecules, reducing its surface tension, making bubble-making possible.

It is possible to get longer-lasting, sturdier bubbles by adding glycerine (also spelt ‘glycerin’). A sweet-tasting substance used for sore throats (you can buy it from supermarkets and pharmacies), glycerine has a special ability of slowing down how quickly water can evaporate. Free-floating bubbles eventually pop when the water in its wall evaporates, but glycerine molecules will form weak bonds with water molecules, ‘sticking’ them together and keeping the water inside a bubble’s wall inside for longer.

If you like, you could add glycerine to your bath water for an especially frothy and sweet cleanse. More cheerful and cleaner – hurray for longer lasting bubbles!

Answer by Dr Stu

Question sent from ‘JJ’

Image source: croc attack!!! by Nizam Uddin, on Flickr

Article by Stuart Farrimond

August 21, 2014

Doctor Stu is editor of Guru Magazine. He originally trained as a medical doctor before deciding to branch out into lecturing, writing, editing and science communication. He drinks far too much coffee, eats lots of ice cream and has a bizarre love of keeping fit.
You can check out Doctor Stu’s blog at realdoctorstu.com or his poncy personal website stuartfarrimond.com. Here's his .

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