Thursday, April 21, 2011

EGGperience the Pressure

Why can’t I get jar lids off sometimes? It is all to do with air pressure.  The next demonstration shows how air pressure works and will leave you with a curiosity to show your friends. 

For this experiment you will need:

  • 1 Peeled boiled egg
  • 1 Glass bottle with a wide neck
  • Boiling water 
  • Oven gloves
  • 1 Adult to help you out 

Take the bottle and fill it with boiling water. Leave for a bit so the bottle gets nice and hot.  Using your oven gloves, pour the water out and place the bottle on a flat surface.  Sit the egg on the bottle (narrow end first).  Now just watch.  The egg should get sucked into the bottle.

Why?  First a small bit of air sneaks out of the bottle past the egg.  Then, as the hot air cools it that air shrinks – taking up less space.  The steam inside the bottles cools too and turns into water – taking up less space. 

This process results in the air pressure on the outside of the bottle becoming greater than on the inside.  It’s this pressure that pushes and pulls the egg into the bottle.

Maybe your egg popped?  Why do you think it has done this?

Don’t give up if you have problems getting this to work.  So did we!  Make sure the water and the bottle are super-hot.  If the egg splits it might be that the bottle neck is too small.

So the next time you can’t get the lid off a jar just try standing it in hot water. This will change the air pressure in the jar and it should become easier to get the lid off.   

Check back tomorrow for more eggperiments!