Can Crush Practical

that attracts attention.

 

 

 

Category - Solids, Liquids & Gases

Key Idea - Air Pressure

 

Purpose - I have used this to show the effects of a vacuum and also when teaching the concepts of liquids vs. gases 
Nature -  Class Practical
Materials -  empty soft drink cans, Bunsen burner, tripod, gauze mat, beaker tongs, bucket or sink of cold water
Method - 
  1. Place about 2 cm of water into the soft drink can
  2. Place can to heat
  3. Once water is boiling well fold the paper towel into a sling to enable the hot can to be lifted.
  4. Quickly invert the can into the cold water making sure the mouth is well under the water.
  5. Note the quick imploding of the can.
Safety - Usual procedures with heating.  Students should be made aware of the risks involved with moving containers of hot water very quickly.
Explanation - As the water boils the vapour fills the tin, forcing air out to make room. When it is immersed in cold water the water vapour in the tin quickly condenses, leaving a vacuum that cannot be filled because the mouth of the tin is below the water.  Air pressure does the rest!
Notes -

Students love this prac and always want to do more than the number of tins supplied.  I have sent kids out to clean up the school yard, looking for more tins to implode! 

This can be introduced with great style with the Can Crush Demo.