SafekipediaLiquid air is a special form of air that has been cooled to very cold, or cryogenic temperatures, turning it into a pale blue liquid. Because it is extremely cold, liquid air needs to be kept in special containers, like vacuum flasks, to protect it from warming up to room temperature. When liquid air absorbs heat, it quickly changes back into a gas.
This interesting substance is very useful in industry. It helps scientists and engineers separate air into its individual parts, such as nitrogen, oxygen, argon, and other inert gases, through a process known as air separation (also called air rectification). These gases are important for many different jobs, from making steel to helping people breathe in hospitals. Liquid air’s ability to change temperature quickly makes it a valuable tool in many scientific and industrial jobs.
Properties
Liquid air is a very cold, pale blue liquid that forms when air is cooled to extremely low temperatures. It is much denser than regular air, weighing about 870 kilograms per cubic meter. This density changes slightly depending on the exact mix of gases in the air.
Liquid air boils at around -194 degrees Celsius, which is colder than liquid nitrogen but warmer than liquid oxygen. Keeping it at a steady temperature can be tricky because the nitrogen in it tends to turn back into a gas first, leaving behind more oxygen. This can change the boiling point of the remaining liquid.
Preparation
Liquid air is made by cooling regular air to very cold temperatures where it turns into a liquid. This is done using special machines that compress and cool the air. The first time scientists turned air into a liquid was in 1883 by two Polish scientists.
One common way to make liquid air today uses a process called the Hampson–Linde cycle. This involves pressing air very tightly and then letting it expand, which makes it very cold. This cold air can be used for experiments or, as some companies have tried, to power vehicles. In 2012, experts said liquid air might be a good way to store energy for future use.
This article is a child-friendly adaptation of the Wikipedia article on Liquid air, available under CC BY-SA 4.0.