All matter is made of tiny particles arranged differently in solids, liquids, and gases. In solids, particles are tightly packed in a fixed pattern, vibrate in place, and have very strong forces of attraction, giving them a fixed shape and volume. In liquids, particles are close but irregular, can slide past each other, and have moderate attraction, giving them a fixed volume but no fixed shape. In gases, particles are far apart, move freely and rapidly, and have very weak attraction, so they have no fixed shape or volume and can be compressed easily. Mass is the amount of matter in an object, and volume is the space it takes up. Physical properties like shape, size, color, density, and melting or boiling point help describe matter.