- noun a colourless odourless non-flammable atmospheric gas. It is used in photosynthesis and given off in aerobic respiration.
- Gas found in the atmospheres of the Earth, Venus and Mars. On Earth it is produced mainly by volcanoes and was the atmosphere’s dominant active component (nitrogen, the main component of the atmosphere, is very inert chemically) until photosynthesis began and oxygen was produced.
- noun a colourless, odourless, non-toxic gas found in the atmosphere, and also used in fire extinguishers and fizzy drinks
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- noun a colourless, odourless, non-toxic gas, a natural constituent of the atmosphere and a product of breathing and some combustion processes.
- The gas produced when the carbon in foods is oxidized either by the action of yeasts and other microorganisms, by combustion or by cellular processes in the body, or when chemical raising agents are heated or react in water. The gas is responsible for the raising of bread, cakes, etc.
- noun a colourless gas produced by the body’s metabolism as the tissues burn carbon, and breathed out by the lungs as waste
- a colourless, odourless gas that occurs naturally in air and is a by-product of fermentation. In still wines the wine is fermented in an open container to allow the carbon dioxide to disperse; in sparkling wines the wine is fermented in a sealed container to force the carbon dioxide into the liquid. Carbon dioxide is also sometimes used at other stages of winemaking to displace oxygen and reduce oxidation. Some winemakers now also bottle white wines with some dissolved carbon dioxide to improve freshness and fruitiness.