Chemistry: Bonding in Water Molecules

Bonding in Water Molecules

• Covalent bonds are present in the water molecule.

Hydrogen Bonding

• Hydrogen bonds are weak molecular forces that form between a positive hydrogen atom and a negative oxygen atom.
• They are responsible for the cohesion and adhesion properties of water.

Labelling a Hydrogen Bond

• A diagram of a hydrogen bond would show a positive hydrogen atom bonded to a negative oxygen atom, with a dashed line representing the weak molecular force.

Properties of Water

• Cohesion: the bonding of two molecules of the same type, e.g., water molecules in a plant, allowing water to be transported from the roots to the top through hydrogen bonds.
• Adhesion: the formation of hydrogen bonds between water and other polar molecules, causing water to stick to them, e.g., water evaporating from xylem vessels in plants and condensing on walls.
• Latent heat of vaporization: the heat required for a molecule to evaporate and become vapor, e.g., the energy needed to boil water.
• High boiling point: the highest temperature a liquid can sustain, e.g., water boils at 100°C.
• High specific heat capacity: the amount of heat or energy water can absorb before the hydrogen bonds break, e.g., water's ability to maintain a cool temperature despite being heated.

Hydrophilic and Hydrophobic Substances

• Hydrophilic: a substance that is attracted to water, e.g., sugar, which absorbs water well.
• Hydrophobic: a substance that repels water, e.g., oils, which cannot mix with water.