State of matter
The material around us exists in three states (solid, liquid, gas) depending on temperature. Solids do not change shape and volume like ice, trees, and so on. The liquid has the property of flowing like water and juice, and the shape changes according to the vessel, but the volume does not change at a constant temperature and pressure. Gases such as air and carbon dioxide are not uniform in shape and volume, and the volume of the gas varies greatly with temperature and pressure.
When the ice is heated, it becomes water. When the water is heated continuously, it becomes water vapor. Conversely, when water vapor cools, it becomes water, and when water is cooled, it becomes ice. When a substance is heated or cooled, the state of the substance changes, which is called a state change.