Tangible Science: Cavitation

*Adult Supervision Required*

Could you break a glass bottle using science? Is there a way you could use your hand to shatter the bottle, without hitting it against anything? 

If you’d like to do this experiment yourself, you will need: a glass bottle, water, something to break the bottle into (like a bucket or a box), we also recommend a t-shirt to pad your hand.

Let’s break some bottles:

  1. Fill your glass bottle with water, up to the start of the neck.
  2. Wrap the t-shirt around your dominant hand tightly, and use your other hand to grab the bottle by the neck.
  3. Hold your bottle over your bucket, and hit the top of the bottle with the palm of your hand as hard as you can. If you hit the top hard enough the bottom will blow out, breaking your bottle! Don’t believe that it’s possible? Check out this video:

Now this is very cool, but what actually happened to the bottle?

When you are holding the bottle still, only gravity is acting on the top of the water. When you hit the top of the bottle, your hand accelerates the glass bottle and fluid, and this increase in acceleration causes the water at the bottom of the bottle to become water vapor, while the rest of the water remains at normal water pressure. This difference in pressure causes cavitation, which is the formation of vapor cavities in a liquid, the same as water “bubbles” that you see during water boiling, resulting in the glass exploding. This is an example of fluid dynamics in action.

So there you have it, if anyone asks if you can break a bottle using science, you know you can!

 

Author: Leo Borasio