What you need:
A mineral water bottle made of thin plastic (ones with small caps tend to work best)
A few drops of water leftover in the bottle.
All your strength!
What to do:
1. Start by pressing at the centre of the bottle, pinching its walls together.
2. Then twist the lower part of the bottle.
3. Hold the bottle like that and unscrew the cap. Squeeze to let the air escape and screw the cap back.
4. Twist the bottle again until you find that it’s getting harder to do so. Get an adult to help you if you find the process taxing.
5. Once you feel you can’t twist the plastic any more, point the head of the bottle away from yourself and others (and from breakable items!). Keep the twisty pressure on the bottle and unscrew its cap with your thumb.
What happens?
If all goes well, the cap just pops off and goes flying. Also, you see white smoke rising out of the bottle.
Why?
While you’ve been twisting the bottle, you’ve been forcing the air inside it to be compressed into an increasingly smaller space. The pressure builds so much that the cap simply pops off.
As the pressure increases inside the bottle, so does the temperature. The rise in temperature causes the leftover water in the bottle to turn into water vapour.
This is the smoke you see escaping from the bottle when you the lid
If you miss even one part of this, straighten the bottle, blow some air in it and try again.
Picture Credit: Google
