What is carbon dioxide?

  • Carbon dioxide is a compound. Its molecules consist of one carbon atom joined to two oxygen atoms.

  • In the atmosphere, carbon dioxide is a greenhouse gas.

  • We use carbon dioxide to make drinks fizzy and keep foods fresh.

Get an introduction to the chemistry of carbon dioxide from a development engineer.

Structure and properties

At room temperature carbon dioxide is a colourless and odourless gas.

The carbon dioxide molecule is made up of one carbon atom joined to two oxygen atoms. This means it has a chemical formula is CO₂.

carbon dioxide molecule

CO₂ in the atmosphere

The amount of carbon dioxide in the atmosphere is maintained through a balance.

Processes that increase the amount of CO₂ in the air include:

  • combustion of petrol and diesel in cars.
  • respiration of living things.

Processes that decrease the amount of CO₂ in the air include:

  • photosynthesis by plants which converts carbon dioxide and water to make their own food, glucose.
  • dissolving in sea water.
The earth's atmosphere
The main gases that contribute to the greenhouse effect are carbon dioxide, methane and water vapour.

Carbon dioxide makes up less than 1% of the atmosphere; however, it is an important greenhouse gas.

This means that its molecules in the atmosphere absorb radiation, keeping the Earth warmer than it would otherwise be.

For the past 100 or so years, carbon dioxide has been added to the atmosphere more quickly than it is removed. The extra carbon dioxide contributes towards global warming.

Global warming leads to climate change, including more frequent droughts and stronger storms.

Carbon dioxide quiz

Find out how much you know in this quick science quiz!

Where next?

Discover more about this topic from around Bitesize.

What is carbon?
How to make CO₂
What are carbohydrates?