A gas is a state of matter that has no fixed shape or volume. Gases are characterized by their ability to completely fill any closed container, and their properties depend on the volume of the container but not on its shape. Gas particles are more distant from each other than in liquids, and they move very fast and collide with one another, causing them to diffuse or spread out until they are evenly distributed throughout the volume of the container. Gases have a lower density than other states of matter, such as solids and liquids.
Here are some key facts about gases:
- A gas is a substance made up of high-energy particles that are constantly moving and colliding with each other and the walls of their container.
- Gases have neither a definite size nor shape, whereas ordinary solids have both a definite size and a definite shape, and liquids have a definite size, or volume, even though they adapt their shape to that of the container in which they are placed.
- Gases will completely fill any closed container; their properties depend on the volume of a container but not on its shape.
- A gas may be either a pure substance or a mixture.
- Examples of gases include air, water vapor, and helium.
