This document describes the key properties of solids, liquids, and gases. It explains that solids maintain their shape unless a force is applied, liquids take the shape of their container but maintain a constant volume, and gases spread out to fill their container. The document then discusses that all materials are made of tiny particles, and that the position and behavior of these particles differs between solids, liquids, and gases. It provides a link to a video about particles and assigns students a task to match states of matter to their properties and depictions of particle arrangement.