Carbon-Dioxide

Carbon dioxide is a colorless, odorless gas made of one carbon atom and two oxygen atoms that makes up about 0.03 percent of the atmosphere. It naturally circulates through living organisms, volcanic activity, and chemical processes.

Sources of carbon dioxide

• Humans and animals breathe in oxygen and release carbon dioxide, while plants take in carbon dioxide and release oxygen during gas exchange.
• Hot, red-glowing magma found inside volcanoes releases carbon dioxide into the air.
• The natural decomposition of dead plants and animals adds carbon dioxide to the atmosphere.
• Burning fossil fuels such as coal, oil, and petrol produces carbon dioxide.

Physical properties

At room temperature, carbon dioxide exists as a dense gas that has no color and no smell. It is non-combustible and does not support burning because its oxygen is already bound to carbon. Lowering its temperature turns it into a solid called dry ice, while reducing its temperature and increasing pressure converts it into a liquid.

Chemical reactions

• Carbon dioxide does not have combustibility, meaning it will neither catch fire nor help other materials burn.
• It reacts with metals, combining with sodium to produce sodium carbonate and carbon, or with magnesium to yield magnesium oxide and carbon.
• Being acidic in nature, it reacts with bases such as sodium hydroxide to produce water and sodium carbonate, a salt used as washing detergent.
• It reacts with lime water, also known as calcium hydroxide, to form calcium carbonate and water.
• When mixed with water, it forms carbonic acid, which creates the fizz and rising bubbles in carbonated drinks.

Everyday uses

Carbon dioxide is filled into red fire extinguisher cylinders to put out flames because it does not burn. When reacted with ammonia, it forms fertilizers used as manure for plants. In its solid state as dry ice, it provides cooling in refrigerators. It is also used in food preservation to keep fruits, chicken, and mutton fresh.