The gas state is one of the three primary states of matter, alongside solids and liquids. In this state, particles are widely spaced and move freely, allowing gases to fill any container they occupy. This behavior is due to the high energy of gas particles, which overcomes the attractive forces between them. Gases have no fixed shape or volume, meaning they can expand or compress easily. Common examples of gases include oxygen, carbon dioxide, and nitrogen. The properties of gases are described by various laws, such as Boyle's Law and Charles's Law, which explain how pressure, volume, and temperature are related.