The property of water that allows it to exist in three states—solid, liquid, and gas—is its unique molecular structure and hydrogen bonding. Water molecules consist of two hydrogen atoms bonded to one oxygen atom, forming a bent shape. This structure allows water to form strong hydrogen bonds, which give it a relatively high boiling point, melting point, and surface tension. As a result, water can transition between states depending on temperature and pressure: ice (solid) at low temperatures, liquid water at moderate temperatures, and steam (gas) at high temperatures.