Liquids have characteristics that fall somewhere in between those of solids and gases, yet they resemble solids more. Intermolecular forces, as opposed to intramolecular forces, such as the covalent bonds that bind atoms in molecules and polyatomic ions, keep molecules in a liquid or solid together. In comparison to covalent bonds, intermolecular forces are often significantly weaker. For instance, in 1 mol of water, the intramolecular forces must be overcome in order to break both O-H bonds, while the intermolecular forces must be overcome in order to turn 1 mol of liquid water into water vapor at 100 °C, which needs just around 41 kJ. (Despite this figure appearing to be modest, the intermolecular forces in liquid water are some of the highest intermolecular forces ever measured.