Monday 30 April 2012

The self-crushing can!


The self-crushing can!

This is a brilliant experiment to show what keeps us from being crushed in our atmosphere.  It’s all about pressure.

How to do the experiment...

First you will need...

·         Tongs
·         An empty clean can
·         Water
·         A cold tank or sink of water
·         A Bunsen burner or a hot plate

What you will need to do is...

Put a little water in the bottom of the can.

Heat the can up (use the tongs to hold the can for safety) from the bottom until lots of steam rises.

Turn the can upside down

Plunge into the VERY COLD WITH PLENTY OF ICE water! 

What happened? 

Why do you think it did that?

Here's an explanation of what happened
An empty can doesn’t crush because the air particles inside the can are the same as outside of the can as air is able to flow easily into the can, therefore the pressure in the can is equal to the pressure outside the can, stopping the can from being crushed.  So how do we change this?   Well, when we put a little bit of water in the can (just a little) then we add some heat (energy) this makes the air molecules move about faster and some of them escape to make room.   The pressure inside the can is still the same as outside.
Flipping the can upside down and put the can under the cold water the water closes off the opening of the can, no more air can more in or out of the can.  Now the air molecules that were full of energy bouncing around the can is cooled by the cold water; this changes the amount of pressure in the can as the air molecules condense and move closer inside the can, thus making the pressure outside more than the pressure inside.  What we have done is create a vacuum inside the can!

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