Daily Idea #357: Bottle Top Pop

While standing in line for something the other day, a family friend showed us this trick and I knew right away it was going to be a daily idea. So, thank you for the science trick (you know who you are)!

All you need is an empty water bottle— one that has thinner plastic is better (don’t forget to recycle it when you are finished). This experiment will pop the cap off forcibly so be very careful not to point it at anyone.

Start by unscrewing the cap enough that it is still on the bottle airtight, but loose enough that you can flick it off easily with your thumb or finger. Grab the bottle at both ends and twist— twist hard enough that it creates a small “waist” in the middle of the bottle. You may notice that the bottle has heated up a tiny bit; increasing the pressure in the bottle increases the temperature. While holding the tension in the twist, flick the cap with your finger to finish unscrewing it and watch the cap fly across the room. You might see some mist released when the cap flies off (if you want to increase the vapor mist, put a small drop of hand sanitizer in the bottle before you twist); by increasing the pressure inside the bottle you have raised the temperature. When the pressure is released quickly, it causes left over water droplets to form a gas. By quickly releasing the pressure, you drop the temperature quickly making the water vapor (which you cannot see) turn into tiny water droplets (which you can see).

You can repeat this as many times as you want by blowing air back into the bottle and repeating the steps. If the bottle gets any cracks in it, it will no longer work.