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Chemistry is all around us
Copyright 2015
This project has been funded with
support from the European Commission

Educational Packages

Chemistry in Everyday life

Carbon cycle


Have you ever unintentionally burnt a slice of bread in the toaster? The blackness you notice over the burnt bread is because of the traces of burnt carbon. Carbon exists in both mineral form (such as coal, diamond, carbon dioxide in das form or dissolved in water) and in organic form.

  1. Atmosphere: Carbon dioxide
  2. Hydrosphere: Carbon dioxide, bicarbonate
  3. Lithosphere: Petroleum, coal, natural gas, carbon
  4. Biosphere: Organic molecules within the organism

Most of the carbon in the nature is present in the form of carbon dioxide. The carbon from the carbon dioxide is very significant for photosynthesis. The carbon dioxide in air is used in the process of photosynthesis together with water and nutritional salts.

Organic carbon, which is the building block of living organisms, is generated through the process of photosynthesis from the carbon dioxide gas available in the atmosphere or dissolved in the sea water.

Green plants, animal and vegetal parasites recycle carbon into carbon dioxide gas by decomposing organic matter. The residues, feces and corpses also decompose recycling the carbon dioxide present in their structure.

As seen in the figure, carbon dioxide that is present in the atmosphere in gas form and in the hydrosphere in dissolved form is the main source of carbon for living organisms. A part of the carbon within the animal body is recycled back into the atmosphere as CO2 through respiration in the mitochondrion.

Food + Oxygen --> Water + Carbon dioxide + Energy


The carbon in the remains and the wastes of all organisms is released back in the form of CO2 following a series of events such as putrefaction and decomposition – Fermentation.

A portion of the organic carbon is accumulated in fossil fuels such as coal and petroleum. An abundant amount of carbon dioxide is released into the atmosphere through their combustion. A major portion of this is rapidly transferred into the seas and the oceans and is accumulated in the form of carbonates. Additionally, volcanic eruptions also release a considerable amount of carbon dioxide into the atmosphere.

Daily Life Informtaion Regarding The Carbon Cycle

The carbon cycle takes place among the atmosphere, lithosphere, hydrosphere and the biosphere. Unless the cycle is interrupted, the carbon is present in equilibrium in the nature. The amount of CO2 in the atmosphere is fixed and known. If the CO2 taken from the atmosphere were not released back, photosynthetic processes would be reduced gradually and in approximately 35 years, the life as we know would cease on earth as the food chain would be broken. The carbon balance in the atmosphere is also interrupted through the negative effects of man. The amount of carbon dioxide fed into the atmosphere has increased by 25% as a result of industrialization.

The carbon dioxide present in the atmosphere and the water are in equilibrium. The natural source of carbon dioxide in the lithosphere is the volcanoes. Mankind mines and utilizes the fossil fuels more as a result of rapid industrialization, urbanization and population rise. The amount of carbon dioxide released into the atmosphere is increased as a result of the combustion of limestone and fossil fuels such as coal, natural gas and petroleum.

The depletion of the natural vegetation on earth (as a result of forest fires, for instance) also affects the carbon balance significantly. This situation clearly states that the carbon cycle can be altered by artifact causes. The increasing amount of carbon dioxide in the atmosphere will result in an increase of a couple of degrees in the temperature of the earth. As the earth surface gets warmer, the sea level will increase through melting of the glaciers and the earth climate will be altered.

Carbon Dioxide Consumption in Nature
  1. It is used in photosynthesis by the land and the marine plants.
  2. It is used in the shell formation of marine animals.
  3. As a result of the death of the marine animals and plants, the residues sediment on the basin aiding in the formation of carbonated rocks.
  4. The organic carbon remains of the dead organisms transform into fossil fuels such as petroleum and coal in time with the effect of pressure.

Carbon Dioxide Production in Nature
  1. It is recycled back into the nature through respiration of organisms.
  2. Through putrefaction of dead organisms
  3. Through forest fires
  4. Through physical and chemical decomposition of carbonated rocks
  5. Carbon is transferred from air into water and from water into air through the contact of water and air
  6. As a result of volcanic events
  7. Through combustion / burning of fossil fuels.