Properties of Water

  • 2 atoms of hydrogen are covalently bonded to a molecule of oxygen, water is a polar molecule. There are weak hydrogen bonds between each water molecule and it has a high heat capacity.
  • Water has a large latent heat of vaporisation (Energy required to convert it to as gas)
  • Water has strong cohesion between other water molecules
  • Water is a metabolite (required) in many metabolic reactions

Specific Heat Capacity

  • The heat required to raise 1kg of water by 1 degree Celsius.
  • Water has a large heat capacity, and therefore can absorb large amounts of heat energy before temperature increases
  • In animals, water is used as a ‘heat buffer’ which maintains an internal body temperature (homeostasis)
  • In aquatic animals, it also helps them live in a constant temperature environment

Large Latent Heat of vaporisation

  • Water has a high boiling point
  • When a mammal sweats, it evaporates using a lot of energy and can therefore taking that energy away and therefore the mammal loses heat efficiently
  • Water molecules that have evaporated and the energy lost is the latent heat

Strong Cohesion

  • Due to water being polar, water molecules have a strong polarity meaning that water molecules are attracted to each other, and form hydrogen bonds between each molecule; therefore hydrogen bonds help hold water together
  • In plants, water moves up the xylem as a continuous stream. This allows water to reach the top of trees
  • Water cohesion leads to surface tension making water behave if there is a skin which allows for pond skaters for example

Water Solvent

  • Transportation of molecules (Gases such as Oand CO2 and waste product such as NHand urea) are dissolved in water before being moved around the body
  • Inorganic ions are small hydrophilic molecules such as amino acids, monosaccharides and ATP can also be absorbed into water.
  • Enzymes that require a solution
  • Metabolic reactions occur inside each cell in the cytoplasm which contains water


  • Water molecules can also be involved in chemical process e.g. hydrolysis is used in digestion and condensation used in synthesis


The Roles of water in living Organisms:

  • High specific heat capacity allows for a ‘heat buffer’ so there are no massive heat fluctuations as well as allowing for a constant sea temperature in aquatic animals.
  • High latent heat allows for energy to be lost through sweating which allows for heat to be lost, cooling the animal down
  • Cohesion allows for water to be moved up plants
  • Water is a solvent absorbing molecules to be transported around the body
  • Use in metabolism, water is used to break complex molecules in hydrolysis reactions or break down molecules in condensation reactions
  • Water is used in synthesis