Indicate whether each of the following describes a gas, a liquid, or a solid: c. Helium occupies the entire volume of a balloon.

Matter exists in three primary states: solid, liquid, and gas. Solids have a fixed shape and volume, liquids have a definite volume but take the shape of their container, and gases neither have a fixed shape nor a fixed volume, expanding to fill their container completely.

Gases are characterized by their ability to expand and fill the volume of their container. This is due to the high kinetic energy of gas particles, which move freely and are far apart compared to solids and liquids, allowing them to occupy any available space.

The Kinetic Molecular Theory explains the behavior of gases based on the motion of their particles. It posits that gas particles are in constant, random motion and that their collisions with the walls of a container create pressure, which is why gases can expand to fill any volume.