Materials can exist in more than one form; they can be either in a liquid form, or a solid form. These are called states of matter. However, when heated or cooled, matter changes its state. When heated, some solid materials change to liquid, and this process is called melting. When cooled, materials that were in liquid form turn into solid, and this process is known as freezing. Look through the pictures in the worksheet with your students. Ask them what changes of state are shown in the pictures, then trace on the dotted lines to the correct answers.