Water

Properties of Water

  • Water is a simple molecular substance with the formula H₂O.
  • Its molecules are made up of two hydrogen atoms covalently bonded to one oxygen atom.
  • Water has unusually high melting and boiling points due to the hydrogen bonding between its molecules.

Physical State

  • At room temperature, water is a liquid, which is unusual for a molecule of its size.
  • This is due to water’s hydrogen bonds, which are very strong.

Water as a Solvent

  • Water is often called the “universal solvent” due to its ability to dissolve many substances.
  • Dissolved substances can move around and react more easily. It’s why many chemical reactions occur in aqueous solution.

Water and the Environment

  • Water is vital for life, acting as a solvent in which biochemical reactions take place.
  • It’s an important factor in climate regulation as it can absorb and distribute heat.

Hard and Soft Water

  • Water is considered “hard” if it has high concentrations of ions, such as calcium and magnesium.
  • Hard water can cause scale in pipes and reduce the lathering ability of soap.
  • Water is “soft” when it contains very few ions and easily forms lather with soap.

Water Treatment

  • Potable water is water that is safe to drink.
  • Water can come from many different sources and it is treated to make it safe to drink. This removes harmful bacteria, viruses and parasites.
  • Treatment involves processes like sedimentation, filtration and disinfection (usually by chlorination).
  • Fluorides can also be added for dental health, and pH is adjusted to prevent corrosion of pipes.

Water of Crystallisation

  • Water of crystallisation refers to water molecules that are incorporated in the crystalline structure of a chemical compound.
  • This water is often necessary for the compound to maintain its crystal structure, and can be removed by heating (forming an anhydrous compound). For example, blue copper(II) sulfate crystals turn white when dehydrated.

Distillation of Water

  • Distillation is a physical separation process that can be used to purify, or desalinate, water.
  • It involves heating a liquid into a vapour, then cooling and condensing the vapour back into a liquid in a new container.
  • Distilled water is very pure, but also lacks minerals found in natural sources of water.