MCQ Detailed View

Matter exists in three common states: solid, liquid, and gas. Each state has unique physical properties that determine how its particles are arranged and how it occupies space. Among these, it is the gaseous state that fills all the space available to it.

In a solid, particles are tightly packed and held together by strong intermolecular forces. Solids have a definite shape and definite volume, meaning they do not change shape or size to fill a container.

In a liquid, particles are close to each other but can move around more freely than in a solid. Liquids have a definite volume but no definite shape. They take the shape of the container but do not expand to fill the entire available space. For example, water poured into a glass stays at the bottom and does not spread to fill the whole container.

In contrast, in a gas, the particles are far apart and move randomly at high speeds. The intermolecular forces between them are very weak. Because of this, gases have neither a definite shape nor a definite volume. Instead, they expand freely and distribute themselves evenly to occupy all the space available within a container. For example, if oxygen is released into a room, it quickly spreads to fill the entire room.

This property of gases is explained by the kinetic molecular theory, which states that gas molecules are in constant motion and collide with each other and the walls of the container. The pressure of a gas arises from these collisions.

Therefore, the correct answer is Gas, since only gases expand to completely fill any container or space provided to them. This property is fundamental in understanding air, atmosphere, and various applications in physics, chemistry, and everyday life.