Balloon Blowout

Balloons, bottles and one heck of a bang! This explosive chemical investigation isn’t for the faint hearted and can even make the faint of hearing jump.

Australian Curriculum links

  • Science > Chemical Sciences > Year 2 > ACSSU031
  • Science > Chemical Sciences > Year 5 > ACSSU077
  • Science > Chemical Sciences > Year 6 > ACSSU095
  • Science > Chemical Sciences > Year 8 > ACSSU225
  • Science > Chemical Sciences > Year 9 > ACSSU179

You'll need

  • 2 heaped teaspoons of bicarbonate of soda
  • 150 mL vinegar
  • plastic drink bottle (600 mL)
  • balloon
  • funnel

Try this

  1. Insert the funnel into the neck of the balloon and spoon in the bicarbonate of soda, shaking it into the round part of the balloon.
  2. Use the funnel to pour the vinegar into the plastic bottle.
  3. Hold the balloon so none of the bicarbonate of soda falls out and carefully stretch the neck of the balloon over the neck of the plastic bottle.
  4. Hold the neck of the balloon firmly on the plastic bottle and shake out the bicarbonate of soda so it falls into the vinegar.

What's going on?

Just like the aliens in some sci-fi movies, humans and other mammals also have acid in their blood. When you breathe in the cells in your body use oxygen and make carbon dioxide. This carbon dioxide travels around your body in your blood as carbonic acid. The carbonic acid is turned back into carbon dioxide before it is removed from the body via your lungs when you breathe out.

If you can’t breathe normally or your blood isn’t circulating normally you could accumulate too much carbonic acid in your body. This is very dangerous because it means your enzymes – special proteins in your body that make chemical reactions happen – may stop working. As a result your organs stop working and your entire body could shut down!

When bicarbonate of soda and vinegar mix, a chemical reaction occurs and one of the products of this reaction is carbon dioxide gas. Carbon dioxide keeps on being made until there is no vinegar or bicarbonate of soda left to react. So much gas is produced that it not only fills up the bottle but fills up the balloon as well, resulting in an explosive finale.

The reaction of bicarbonate of soda with vinegar is known as an acid-base reaction. The bicarbonate of soda is the base and vinegar is an acid, otherwise known as acetic acid. These kinds of reactions generally produce water and a salt – although not the kind of salt that you normally cover your hot chips with, that’s called sodium chloride. The name of the salt formed in this reaction is called sodium acetate.

If you want to get technical about things we can write out what’s happening as a chemical equation:

acetic acid + sodium bicarbonate → salt + gas + water
CH3COOH + NaHCO3 → NaCH3COO + CO2(g) + H2O

This reaction doesn't just happen in one big step. Instead, it first produces the salt and a chemical called carbonic acid. The carbonic acid then breaks down to form carbon dioxide gas and water:


carbonic acid → carbon dioxide gas + water
H2CO3 → CO2(g) + H2O

A similar reaction is the reason why self raising flour makes cakes, biscuits and breads rise.

Real world links

Self raising flour normally contains baking powder which is a mixture of bicarbonate of soda and a mild acid. Moisture from water, milk or egg in the cake mixture dissolves the powder and they then react with each other. The carbon dioxide gas released by the reaction is what makes the food rise.