Fizzy drinks

Find out what's really in those bubbles that give your drinks their fizz.

By: The Small Matters team (Programme and web teams)

  • Duration 5 mins
  • Updated Monday 26th September 2005
  • Introductory level
  • Posted under Chemistry
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The bubbles in fizzy drinks are caused by carbon dioxide (CO2). Carbon dioxide is a colourless odourless gas that dissolves in water under pressure.

The carbon dioxide forms a very weak carbonic acid, (H2C03) which causes the tingly sensation on your tongue. The amount of carbonic acid created depends on the pressure.

A carbonated drink [Image: Mademoiselle Antonova under CC-BY-NC-ND licence] Creative commons image MademoiselleAntonova via Flickr under Creative-Commons license
Carbonated drink [Image: Mademoiselle Antonova under CC-BY-NC-ND licence]


Removing the top from a carbonated drink bottle releases pressure and causes the excess carbon dioxide molecules to come out of solution, as bubbles.

The liquid is, however, still supersaturated and will continue to release the carbon dioxide until it goes "flat".

Carbon dioxide

Carbon dioxide is a very stable compound, which doesn’t burn or support combustion.

If it’s cooled to -79.9 degrees Celsius it immediately forms a solid called ’dry-ice’.

There is no liquid phase. Conversely, warming dry-ice turns it directly back into a gas by a process called ’sublimation’.



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