1.7.3

Properties of Water

Test yourself

Useful Properties of Water

Water is a major component of cells and is essential to life as we know it (60–70% of the human body is made up of water). The properties of water that make it such a useful substance are:

Illustrative background for Good metabolite Illustrative background for Good metabolite  ?? "content

Good metabolite

  • Water is used or formed in many metabolic reactions, such as condensation and hydrolysis reactions.
    • ATP + H2O → ADP + Pi + energy
      • A bond is broken and a water molecule is used up and so this is a hydrolysis reaction.
    • ADP + Pi + energy → ATP + H2O
      • A new bond is formed and a water molecule is released and so this is a condensation reaction.
Illustrative background for High heat of vaporisationIllustrative background for High heat of vaporisation ?? "content

High heat of vaporisation

  • The specific latent heat of vaporisation is the amount of energy needed to change 1 kg of a liquid substance to a gas.
  • As liquid water heats up, hydrogen bonding makes it difficult to separate the water molecules from each other. This means that a lot of energy is needed for water to evaporate.
    • When water evaporates, energy is used up - this cools the environment where the evaporation is taking place.
    • This is why sweating helps with body temperature regulation.
Illustrative background for High heat capacityIllustrative background for High heat capacity ?? "content

High heat capacity

  • Specific heat capacity is the amount of heat one gram of a substance must absorb or lose to change its temperature by 1oC.
  • Water has a high heat capacity so takes a long time to heat and cool.
    • The specific heat capacity of water is much larger than sand. This is why land cools faster than the sea.
    • Water is used by warm blooded animals to more evenly disperse heat in their bodies.
Illustrative background for Good solventIllustrative background for Good solvent ?? "content

Good solvent

  • Water is a good solvent because ions and polar molecules can easily dissolve in it.
  • Water is a polar molecule. This means that the positive end of the water molecule attracts negative ions and the negative end will attract positive ions.
Illustrative background for Cohesive propertiesIllustrative background for Cohesive properties ?? "content

Cohesive properties

  • The strong attraction between water molecules due to hydrogen bonds is called cohesion.
  • Cohesion produces surface tension where water meets air.
    • This is why water forms droplets when placed on a dry surface rather than being flattened out by gravity.
    • Plants use this natural phenomenon to help transport water from their roots to their leaves.

Jump to other topics

1Biological Molecules

2Cells

3Substance Exchange

4Genetic Information & Variation

5Energy Transfers (A2 only)

6Responding to Change (A2 only)

7Genetics & Ecosystems (A2 only)

8The Control of Gene Expression (A2 only)

Go student ad image

Unlock your full potential with GoStudent tutoring

  • Affordable 1:1 tutoring from the comfort of your home

  • Tutors are matched to your specific learning needs

  • 30+ school subjects covered

Book a free trial lesson