When water evaporates, are any bonds between \(\mathrm{H}\) atoms and \(\mathrm{O}\) atoms within a molecule broken?

Water, a substance essential for all known forms of life, has a unique molecular structure that explains many of its remarkable properties. Each water molecule consists of one oxygen (O) atom and two hydrogen (H) atoms, forming the chemical formula H₂O. The oxygen atom is more electronegative than the hydrogen atoms, which means it has a stronger tendency to attract electrons. As a result, the shared electrons in the molecule spend more time closer to the oxygen atom, creating a partial negative charge near the oxygen and a partial positive charge near the hydrogens.

This polarity causes the water molecule to have a bent shape, not a straight line, with a 104.5-degree angle between the hydrogens. The molecular structure of water is key to understanding its various phases and the energy changes involved in phase transitions. It also plays a critical role in many chemical, biological, and environmental processes.

Phase transition refers to the transformation from one state of matter to another, such as the conversion of water from liquid to gas during evaporation. In a liquid state, water molecules are free to slide past each other, which allows for fluidity. As heat is applied, the kinetic energy of these molecules increases until they can overcome the intermolecular forces keeping them in close proximity.

During evaporation, a type of phase transition, molecules with sufficient energy can escape into the air as vapor. This phase change requires energy and occurs at the surface of the liquid, where the molecules are less restricted by neighboring water molecules. Understanding phase transitions is important for many applications, including industrial processes, meteorology, and even in culinary practices, as they dictate how substances interact with heat and pressure.

Hydrogen bonds are a type of weak chemical bond that are critical to the properties of water. They form when a hydrogen atom, which is covalently bonded to a highly electronegative atom such as oxygen, experiences an electrostatic attraction to another electronegative atom in a nearby molecule. In water, this typically means oxygen atoms from different water molecules.

Although hydrogen bonds are weaker than covalent bonds (like the strong bonds between the hydrogen and oxygen within an individual water molecule), they are strong enough to impart water with its high boiling point, surface tension, and ability to dissolve many substances. During evaporation, it's these hydrogen bonds that break, allowing water molecules to transition to the gas phase. In contrast, the sturdy covalent bonds within each water molecule remain intact, thus preserving the integrity of the individual water molecules during the evaporation process.