Solid, Liquid and Gas – The Three Forms of Matter All the things around us are made up of matter. Matter exists in three main states – solid, liquid, and gas. Solids have a fixed shape and volume, like a book or a stone. Liquids do not have a fixed shape but have a fixed volume; they take the shape of the container, like water or milk. Gases have neither a fixed shape nor a fixed volume; they spread out to fill the space available, like air. These states can change from one form to another when