Outline how three properties of water enhance its use by living organisms.

Describe the role of ADH in osmoregulation.

Explain how water is moved from roots to leaves in terrestrial plants.

cohesive properties help in transpiration pull/movement of water in plants;
high surface tension allows some animals to stride across its surface;
high latent heat of evaporation/large amounts of energy required for evaporation makes it a good coolant;
high specific heat capacity causes it to maintain environmental temperatures;
low density as ice forms insulation of lakes allowing life below;
transparency for photosynthesis;
transparency for vision in animals;
solvent properties make it the medium for metabolic reactions;
solvent properties allow transport of (soluble) molecules/food;

osmoregulation is control of water balance in organisms/blood/tissues/ cytoplasm;
ADH regulates water levels/solute concentration of the blood;
produced/released when water in blood is too low;
it increases the permeability of the collecting ducts / increase in the reabsorption of water;
leads to more aquaporins (in collecting duct cell membranes);
lower volume/less urine is produced/urine more concentrated;

water enters roots through the root hairs by osmosis;
root hairs provide an extended surface area (for active transport and osmosis);
active transport of ions from soil into the roots (enhances osmotic pressure);
osmotic pressure moves water into the xylem;
water is carried (in a transpiration stream) in the xylem;
adhesion of water to the inside of the xylem helps move water up;
cohesion of water to itself enhances water movement up the xylem;
water diffuses into air spaces (in spongy mesophyll) of leaves;
it passes out through the stomata by evaporation/transpiration;
evaporation sets up a transpiration pull that keeps the water moving;
guard cells control the rate of transpiration pull/evaporation;
xylem vessels are tubes with helical rings to enhance water movement/resist low pressure;

Many did not understand the difference between heat capacity and specific heat capacity. Heat capacity is a property of a quantity of matter. For example, two litres of water has a greater heat capacity than one litre of water. Specific heat capacity is a property of certain substance. Water has a greater specific heat capacity than iron. Nor did they understand why water made for a good coolant. Many focused too narrowly on an aspect of thermal, cohesive or solvent properties rather than discussing these properties from a more "big picture‟ perspective.

The role of ADH was well described an many candidates scored full marks here. Students need to take greater care when using the term concentration as water represents the solvent.

This question was generally well answered.