Final answer:
Water can naturally exist as a solid, liquid, and gas. The density of water varies depending on its state, with water vapor being the least dense, liquid water being the most dense, and solid ice being less dense than liquid water. Heating and cooling water can affect its density.
Step-by-step explanation:
Water is one of the few substances on the planet Earth that can be found occurring naturally in all three states: solid (ice), liquid (water), and gas (water vapor). A significant difference between these states is the density of each state. The vapor state is least dense, while the liquid state is most dense; the solid-state (ice) is less dense than the liquid state. Warm water is less dense than cold water. Therefore, heating and cooling water affects its density.