Gas

In the gas state, particles are widely spaced and move freely in all directions at high speeds. Unlike solids and liquids, gases do not have a fixed shape or volume. They will expand to fill any container they are placed in, and their volume can be easily changed by altering the temperature or pressure. The particles in a gas are in constant, random motion, colliding with each other and the walls of their container. These collisions result in the gas exerting pressure on its container. Common examples of gases include oxygen, nitrogen, and carbon dioxide, all of which are invisible in their gaseous forms.

The behavior of gases is described by several laws, such as Boyle's law, Charles's law, and the ideal gas law, which relate pressure, volume, and temperature. Gases are highly compressible because the particles are far apart, so applying pressure can significantly decrease their volume. As temperature increases, the particles gain energy, move faster, and collide more often, leading to an increase in pressure if the volume is kept constant. This unique characteristic of gases allows for a wide range of applications, such as in airbags, breathing systems, and air conditioning.