Cryogenics is the production of very low temperatures and the study of phenomena at those temperatures. The range of temperatures with which cryogenics is concerned is not precisely defined, but it generally includes temperatures from - 238 degree Fahrenheit (-150 degree Celsius) down to absolute zero (-459.67 degree Fahrenheit, or -273.15 degree Celsius). The coldest temperatures that have been obtained are within a fraction of a degree above absolute zero.

Methods Used to produce a very low temperatures:

• Magnetism is one way to produce ultracold temperatures. Certain materials will become warm when magnetized and cool when demagnetized. By carefully controlling this process, magnetic refrigerators can be made that will reach extremely low temperatures.
• Compressing the gas is another way of producing an ultracold temperature, this is done by removing the heat by means of ordinary refrigeration, and then allowing the gas to expand.

During very low temperatures, certain materials take on a peculiar property. Below are few of the unique properties of very low temperature.

• Liquid helium acts a though it has no viscosity (resistance to flowing), and its thermal conductivity is several hundred times that of copper or silver at room temperature.
• Some metals become superconductive, they lose all resistance to electric current, and current will continue to flow through them even after the power is cut off.

Uses of Cryogenics:

• The main use of cryogenics is the fractional distillation of air to produce oxygen, nitrogen, and other gases. This process requires cooling the air to low temperatures to liquefy the gases in it. Natural gas, oxygen, nitrogen, and other gases are often liquefied for storage and transport because the liquid form occupy lesser space than the gaseous form.

• Cryogenic temperatures are also used in medicine to preserve certain biological substances, like bull semen (for breeding purposes), whole blood, and bone marrow.

Uses of Liquefied Gases:

• Liquefied gases are used as coolants in various industrial processes.
• Liquid nitrogen is used to freeze foods quickly.
• Liquid nitrogen in medicine, it is used to chill a needlelike instrument called a cryoprobe. Cryoprobe is used by Doctors to freeze and destroy certain kinds of tissue, including warts, skin tumors, eye tumors etc.