Water is a liquid at room temperature because the hydrogen bonds within its construction are weak. These weak bonds hold water molecules together for mere milliseconds, which keeps water in a constantly liquid state at room temperature.
Room temperature is defined as anywhere from zero to 100 degrees Celsius. In other temperatures, water can also be a gas or a solid. Water becomes a gas when the hydrogen bonds that form molecules move quickly. Water becomes a solid, or frozen, when the molecules are slowed down. Water changes easily between its three forms.
To change from a gas to liquid requires the process of condensation. A liquid-to-solid transformation is known as freezing, and a solid-to-gas transformation is known as sublimation. During this process, water changes from ice to water vapor. The changing of water from liquid to gas is known as evaporation.
This process is easily performed by watching the level of water go down as a pot boils on a stove. If the water is left to boil unattended, at some point the pot is emptied of water. The change from a solid to a liquid is known as melting, such as when ice thaws in the spring. Water also rarely changes from a gas directly to a solid, known as the process of front formation.