Britannica Sources used in this answer

Why is water a liquid at room temperature?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

principles of physical science Figure 1: Data in the table of the Galileo experiment. The tangent to the curve is drawn at t = 0.6.

Water is a liquid at room temperature primarily due to the presence of hydrogen bonding between its molecules.12

Although water ( $H_{2} O$ ) is a small molecule, these intermolecular forces create a significant attraction between adjacent water molecules. In the liquid state, water molecules form a polymeric structure—chains of molecules connected by these weak hydrogen bonds. While these bonds are constantly breaking and reforming due to thermal agitation, they are strong enough to keep the substance in a liquid phase over a much wider temperature range than would be expected for a molecule of its size.321

Without this extensive hydrogen bonding, water would likely exist as a gas at room temperature, similar to its heavier analogues like hydrogen sulfide. The energy required to break these hydrogen bonds and permit vaporization is only available at higher temperatures, which is why water has a boiling point of 100 °C (212 °F).23