What you need:
A Styrofoam glass, a pressure cooker, a gas stove, a metal grate. a heatproof plastic bowl, water, timer
What to do:
1. Cover the bottom of the pressure cooker with about 2 to 3 cm of water.
2. Place the metal grate in the water then place the bowl on the grate.
3. Keep the Styrofoam glass upright in the middle of the bow
l 4. Close the lid of the pressure cooker and place it on the stove.
5. When the whistle of the cooker begins to hiss, start your timer.
6. For ten minutes, let the cooker do its job. When the time is up, take the cooker off the stove and place it under a cold water tap. This helps to release the pressure immediately.
7. Once the cooker has cooled, open it and take out the glass.
What happens:
The Styrofoam glass has shrunk to less than half its size!
Why?
The glass is made of Styrofoam which is the brand name for expanded polystyrene. It comprises long chains of molecules known as ‘polymers that have been inflated with a gas. That is why Styrofoam feels so light. If you look at the glass carefully, you’ll even see that it contains air pockets.
A pressure cooker works by turning water into vapour. Some of this vapour escapes from the whistle opening in the lid of the cooker, but most of it remains inside the cooker. This hot vapour is what creates the pressure inside the cooker. In our case, the pressure of the water vapour squeezes the air right out of the Styrofoam, causing it to shrink. That’s how you get the little glass.
Picture Credit : Google
