 
Carbon dioxide (CO2) is a colourless, odourless compound, a gas that's naturally present in the Earth's atmosphere. It is a greenhouse gas that plays a crucial role in regulating the planet's temperature. It's also used in various industries, including the food and beverage industry and the oil and gas sector; it also has many medical uses. The carbon dioxide molecule is composed of one carbon atom covalently double bonded to two oxygen atoms. Carbon dioxide gas is denser than air, and is soluble in water. It's mixed with water or other liquids to create carbonated drinks. The gas is not toxic, but at high concentrations it can displace oxygen and cause suffocation. Its low melting and boiling points make CO2 an excellent coolant, and it is widely used in the food and beverage industry to freeze and transport perishable goods. Carbon dioxide is not flammable. It is slightly acidic, and will react with water to form carbonic acid, which can corrode metals and concrete. It is also a good insulator, and is used in some types of fire extinguishers to displace oxygen and smother flames. 
Dry ice is the solid form of CO2, created by cooling and compressing CO2 gas, which causes it to condense into a solid form. Dry ice has a temperature of -78.5°C and is extremely cold, making it dangerous to touch with unprotected skin. It's commonly used as a refrigerant in the food and beverage industry, and can be used to freeze and transport perishable goods. Dry ice is also used in theatrical productions for special effects, as it produces a thick, white fog when it is exposed to air.  The CO2 molecule consists of one carbon atom and two oxygen atoms. The carbon-oxygen bonds are polar, with the oxygen atoms being slightly negative and the carbon atom being slightly positive. This polarity gives CO2 its unique properties, such as its solubility in water and its ability to absorb and re-emit infrared radiation, which contributes to the greenhouse effect.
The concentration of carbon dioxide in Earth's atmosphere is currently at nearly 412 parts per million and rising. This represents a 47 percent increase since the beginning of the Industrial Age, one factor in the onset of climate change. Carbon dioxide plays a role in plant and animal physiology. Animals and plants need to breathe. Breathing is part of a process called respiration. During respiration, a living thing takes in oxygen from the air and gives out carbon dioxide. This process gives animals and plants the energy to eat, grow, and live. In the human body, carbon dioxide is formed within cells as a byproduct of metabolism. CO2 is transported in the blood to the lungs where it is removed from the body through exhalation. CO2 plays various roles in the human body, including regulation of blood pH and respiratory functioning. Fluctuations in CO2 levels are highly regulated and can cause disturbances in the human body if normal levels are not maintained. Lifesaving CPR works because of the composition of the air we breathe out, which is not all CO2. In fact, when we exhale, the composition of the air remains almost the same as the air we inhale, The amount of inhaled air contains 21% oxygen and 0.04% carbon dioxide, while the air we breathe out contains 16.4% oxygen and 4.4% carbon dioxide. |