Water topic 2.2

Question 1

Water structure

Answer 1

Water is made up of two hydrogen atoms covalently
bonded to an oxygen atom (molecular formula: H2O)

Question 2

Polarity

Answer 2

Oxygen has a higher electronegativity and attracts the
shared electrons more strongly, resulting in polarity

Question 3

Hydrogen Bonding

Answer 3

The dipolarity of the water molecule enables it to form polar
associations with other charged molecules (polar or ionic)
Water molecules can also form hydrogen bonds with other
water molecules (between an δ+ hydrogen and an δ– oxygen)

Question 4

Cohesive Properties

Answer 4

Water can form intermolecular associations with other
molecules that share common properties (e.g. polarity)

Question 5

Cohesion

Answer 5

Water can form hydrogen bonds with other water
molecules (cohesion: like molecules stick together)

The cohesive properties of water results in a relatively
high surface tension (can resist low level external forces)

Question 6

Adhesion

Answer 6

Water can form polar associations with charged
molecules (adhesion: unlike molecules stick together)

The adhesive properties of water allow for potential
capillary action (e.g. transpiration stream in plants)

Question 7

Solvent properties

Answer 7

Water is commonly referred to as the universal solvent due to its
capacity to dissolve a large number of substances (ionic / polar)

Large quantities of water molecules can sufficiently weaken
forces (e.g. ionic bonds) and form dispersive hydration shells

Question 8

Hydrophylic

Answer 8

Substances that can dissolve in water, includes glucose, amino acids, sodium chloride, oxygen (low)

Question 9

Hydrophobic

Answer 9

Substances that cannot dissolve in water, includes lipids (fats and cholesterol)

Question 10

Thermal properties

Answer 10

Water has the capacity to absorb large amounts of heat
energy before undergoing a resultant change in state
* Extensive hydrogen bonding must first be broken
These properties make water a very effective coolant
* Evaporation of sweat requires absorption of heat

Question 11

Other properties water has

Answer 11

Water is transparent, allowing light to pass through it
* Important for photosynthesis and also for vision
Water expands when frozen, becoming less dense
* Important for life on Earth as it means ice floats and
the oceans underneath don’t automatically freeze