Canister Poppers

Jumping lids!

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Purpose -

An excellent demonstration of the reaction between a carbonate and an acid.  Can also be used to show the fact that gases require more space than solids or liquids.

Nature - 

Practical

Materials - 

Plastic film canisters with lids, vinegar, baking soda, aluminium foil

Method - 

· One third fill the film canister with vinegar  Use about a 3cm square piece of aluminium foil to make a small boat that just fits into the canister.

· Load the canister with baking soda and carefully float the boat on the vinegar

· Carefully put the lid on the canister

· Keeping your head away from the lid, give the canister a quick shake and put it down.  The lid should pop off from the canister and fly into the air.

· A variation is to just turn the canister over onto it's lid.  In this case the actual canister pops off into the air.

Safety -

General concerns of using a weak acid, especially avoiding contact with eyes. Fast moving canister lids can be a minor hazard as projectiles.

Explanation -

The acidic vinegar and the baking soda react to produce carbon dioxide gas.  This gas is unable to escape and so builds up until it is able to push the lid off the canister with significant pressure.  The reaction of vinegar with baking soda is shown here

NaHCO₃ + CH₃COOH --> CO₂ + H₂O + NaCH₃COO

Notes -

This is probably a experiment best done outside on boards as it is not uncommon for the lids and some vinegar to hit the ceiling.  Some things to try with a class include predicting the effect of variables amount of bicarb soda and vinegar used or the type of film canister used.