Home > Encyclopedia of Science > Gases, Properties of

• Kinetic theory of matter
• Gas laws
• Words to Know
• Some Gases and Their Properties
• Ideal and real gases
• Properties of real gases

Gases are a state of matter characterized by two properties: their lack of definite volume and their lack of definite shape. This definition suggests, in the first place, that a given mass of gas can occupy any volume whatsoever. Imagine a cylindrical tank filled with a small amount of hydrogen gas placed in a chemistry laboratory. If the top is removed from that tank in a room, the gas escapes from the tank to fill the room. If the door to the room is opened, the gas then escapes to fill the building. If the building door also is opened, the gas escapes into the...