States of matter include solids, liquids, and gases which are composed of microscopic particles that behave differently. Solids have a definite shape and volume with particles that are close together. Liquids have a definite volume but no definite shape as their particles have some room to move. Gases have no definite shape or volume as their particles move freely and fill available space. Examples are provided of each state including common solids like gold and rocks, liquids like water and oil, and gases such as carbon dioxide and helium.