Properties of Water

Question 1

Metabolite

Answer 1

Many metabolic reactions require water
e.g
•photosynthesis
•splitting disaccharides to monosaccharides by hydrolysis reactions

Question 2

High latent heat of vaporisation

Answer 2

The evaporation of water requires a lot of energy to break the hydrogen bonds.

When water evaporates from the surface it removes heat and has a ‘cooling effect’
e.g.
•Sweating
•transpiration

Question 3

High boiling point

Answer 3

The continual making and breaking of hydrogen bonds, means that it is a liquid. Therefore difficult for water molecules to escape the liquid

Question 4

Low density of ice

Answer 4

As water is cooled the molecules slow down as they have less kinetic energy, more hydrogen bonds form,
form crystalline structure, which is less dense than liquid water
Therefore, floats and insulate organisms below

Question 5

High specific heat capacity

Answer 5

Large amounts of energy required to increase the temperature of the water.

Therefore, large bodies of water thermostable(don’t change) even when there are large external fluctuations of temperature.

Marine life depends on thermostability.

Question 6

Cohesion

Answer 6

Hydrogen bonds cause water molecules to stick together, this results in the surface tension.
This allows some organisms to ‘walk on water ‘

Water can be transported up xylem in the transpiration stream as cohesion between water molecules makes long, thin columns (difficult to break) and continuous.

ADHESION- when water molecules stick to other surfaces

Question 7

Solvent

Answer 7

•The polarity of water allows it to be a good solvent.
•Any polar molecules like ions will dissolve well in water
•Water molecules tend to cluster around any charged parts of the solute molecules.
This allows metabolic reactions. •Photosynthesis
•Transpiration to take place in solution in the cytoplasm.

Question 8

Transport medium

Answer 8

Since water is a good solvent and remains a liquid over a wide range of temperatures, it’s a good transport medium
e.g.
•plasma in blood
•mineral ions in the xylem

Question 9

Transparent

Answer 9

Aquatic organisms can photosynthesise as the sunlight passes through the water
e.g.
•algae
•seaweed

Question 10

Structure of water

Answer 10

O- slightly negative charge(-)
H- slightly positive charge(+)
overall water has a slight charge= polar molecule.

It contains hydrogen bonds individually-weak
collectively-stronger