Gas is one of the three forms of matter, since every known substance is either a solid, a liquid or a gas. It was during the early 1600s that scientists started to realize that some matter can exist in a form that is similar to air.
Jan Baptista van Helmont, a Belgian chemist and physician, first used the word "gas" in the mid 1600s to describe this invisible form of matter. He invented the word by altering the Greek word "chaos," which means "space." In this way, the word describes the ability of a gas to fill any amount of space.
Many gases were discovered and studied during the 1600s and the 1700s. These gases included hydrogen, oxygen and nitrogen. It was in 1775 that French chemist Antoine Lavoisier made one of the most important of all finds: He identified oxygen as a chemical element.
The first successful attempts to liquefy many gases started in 1823 when a famous English scientist, Michael Faraday, liquefied chlorine.
Three laws explain approximately how the pressure, temperature, volume and the number of particles in a container of gas are related. These laws are Boyle's law, Charles' law and Avogardo's law.
Boyle's law says that the pressure doubles when a gas is compressed to half its volume at constant temperature.
Charles' law states that a gas expands to the same fraction of its original volume with each degree that its temperature rises. It adds that the ratio between the volume of a gas and its temperature remains constant if the pressure does not change.
Avogardo's law says that equal volumes of different gases contain the same number of particles if they all have the same pressure and temperature.
The universal gas law combines Boyle's law, Charles' law and Avogardo's law: The pressure of a gas can be doubled if the gas can be squeezed into one half the original volume.
Boyle's law was first published in 1662 by Irish chemist Robert Boyle. But other chemists had discovered the law earlier. In 1660 and 1661, Richard Towneley and Henry Power of England experimented with air below atmospheric pressure. They found that the product of the air's pressure and volume remained constant.
As a result of additional research in France in 1679 by scientist Edme Mariotte, the law known today as Boyle's law in North America and Great Britain is called Mariotte's law in continental Europe.
Charles' law was discovered in 1787 by French chemist Jacques Alexandre Cesar Charles. He found that carbon dioxide, hydrogen, oxygen and nitrogen all expand at constant rates as their temperatures rise.
Because Charles did not publish his findings, which were later explained in experiments by French chemist Joseph Gay Lussac, Charles' law is sometimes called Gay Lussac's law. Avogardo's law was first proposed in 1811 by Italian scientist and philosopher Amedeo Avogardo.