Cardon dioxide

Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. It is often referred to by its formula CO2. It is present in the Earth's atmosphere at a low concentration of approximately 0.038% and is an important greenhouse gas. In its solid state, it is called dry ice. It is a major component of the carbon cycle.

--Chemical and physical properties
Carbon dioxide is a colorless gas which, when inhaled at high concentrations (a dangerous activity because of the associated asphyxiation risk), produces a sour taste in the mouth and a stinging sensation in the nose and throat. These effects result from the gas dissolving in the mucus membranes and saliva, forming a weak solution of carbonic acid. One may notice this sensation if one attempts to stifle a burp after drinking a carbonated beverage.

Its density at standard temperature and pressure is around 1.98 kg/m³, about 1.53 times that of air. The carbon dioxide molecule (O=C=O) contains two double bonds and has a linear shape. It has no electrical dipole. As it is fully oxidized, it is not very reactive and is non-flammable.

-- Boiling and melting point
Melting point −57 °C (216 K), pressurised
Boiling point −78 °C (195 K), sublimes

-- Production
Dry ice is readily manufactured:

Carbon dioxide is pressurized and refrigerated until it changes into its liquid form.
The pressure is reduced. When this occurs some liquid carbon dioxide vaporises, and this causes a rapid lowering of temperature of the remaining liquid carbon dioxide. The extreme cold makes the liquid solidify into a snow-like consistency.
The snow-like solid carbon dioxide is compressed into either small pellets or larger blocks of dry ice.
Dry ice is typically produced in two standard sizes: solid blocks and cylindrical pellets. A standard block is most common and will normally be about 30 kg. These are largely used in the shipping industry because they sublime slowly due to a relatively small surface area. The pellets are around 1 cm in diameter and can be bagged easily. This form of dry ice is more suited to small scale use, for example at grocery stores and laboratories.

What is carbon dioxide and how is it discovered?
Joseph Black, a Scottish chemist and physician, first identified carbon dioxide in the 1750s. At room temperatures (20-25 oC), carbon dioxide is an odourless, colourless gas, which is faintly acidic and non-flammable.
Carbon dioxide is a molecule with the molecular formula CO2. The linear molecule consists of a carbon atom that is doubly bonded to two oxygen atoms, O=C=O.
Although carbon dioxide mainly consists in the gaseous form, it also has a solid and a liquid form. It can only be solid when temperatures are below -78 oC. Liquid carbon dioxide mainly exists when carbon dioxide is dissolved in water. Carbon dioxide is only water-soluble, when pressure is maintained. After pressure drops it will try to escape to air, leaving a mass of air-bubbles in the water.
二氧化碳 (carbon dioxide，CO2)Colourless、Odourless。分子量44.01，Density1.527g/L，solubility in water 171ml/100ml(0℃)和 36ml/100ml(60℃)。sources is From air， Use in daily was in Soft Drink, Beer etc...，Fire Extinguisher, Dry ice & NaHCO3

去書店找一本教科書叫 Living Science 2A

2007-05-27 13:27:41 補充：
is carbon dioxide