### Theory:

Carbon dioxide is a chemical compound in which a carbon atom is bonded to two oxygen atoms. The formula $$CO_2$$ represents it. It is present in the Earth's atmosphere, and it sends back the solar energy reflected by the Earth's surface to make use of it for living organisms to survive. When carbon dioxide accumulates more in the atmosphere, it produces a harmful effect.

Occurrence:

$$CO_2$$ is present in the air to the extent of about $$0.03%$$ in volume. It is evolved during the respiration of plants and animals. Also, it is produced during fermentation reactions. Most of the naturally occurring $$CO_2$$ is emitted from the magma through volcanoes. $$CO_2$$ may also be derived from the biodegradation of oil and gases. Man-made $$CO_2$$ in the atmosphere has increased global temperature that is warming the planet. While $$CO_2$$ derived from fossil fuel is a minimal component of the global carbon cycle, the extra $$CO_2$$ is cumulative because the natural carbon exchange cannot absorb all the additional $$CO_2$$.

Physical properties:
• $$CO_2$$ is a colourless and odourless gas.
• Heavier than air.
• Does not support for combustion.
• More soluble in water. It changes blue litmus slightly to red. Hence, it is acidic in nature.
•  It can be liquified easily under high pressure and can also be solidified. This solid form of $$CO_2$$ is called dry ice, which undergoes sublimation.
A solid form of carbon dioxide or a dry ice

Do you know?

Sublimation is the process in which a solid is converted into vapour without reaching a liquid state.

Example: Burning of camphor

Burning of champer

Uses:
• Carbon dioxide is used for preparing soft drinks or aerated drinks.
• Used in the fire extinguishers since it is neither combustible nor supports for combustion.
• Used to make sodium carbonate (washing soda) and sodium bicarbonate (baking soda) by Solvay's process.
• Solid carbon dioxide is called dry ice, which is used as a refrigerant.
• $$CO_2$$ gas is used in stage shows and movie effects.
• $$CO_2$$ can be used in the preservation of food grains, fruits, etc.
• Plants utilise carbon dioxide for photosynthesis.
• $$CO_2$$ is used for artificial respiration in hospitals.
• $$CO_2$$ is required for plants that can be replenished by fertilisers. Carbon dioxide is used for making fertilisers. Fertiliser is a chemical compound, which releases nutrients to plants.
Example:
Chemical fertiliser: Urea
Natural fertiliser: Cow dung
Uses of $$CO_2$$
Do you know?

Soda water is nothing but carbon dioxide dissolved in water under pressure. This is called ‘aerated water’.