1.7 Water

Question 1

Water is a … molecule.

Answer 1

dipolar

Question 2

Name 6 properties of water.

Answer 2

• a solvent
• high specific heat capacity
• high latent heat of vaporisation
• a metabolite
• cohesion
• adhesion

Question 3

What is the role of water being a solvent for living organisms?

Answer 3

• many molecules can dissolve in water allowing chemical reactions to occur within cells
• metabolites can be transported efficiently

Question 4

Why is water a solvent?

Answer 4

Water is a polar molecule.

Question 5

What is the role of water having a high specific heat capacity for living organisms?

Answer 5

• allows water to be a suitable habitat
• buffers temperature changes so optimal temperature is maintained → vital in maintaining temperatures that are optimal for enzyme activity

Question 6

What is the role of water having a high specific latent heat of vaporisation for living organisms?

Answer 6

• provides a cooling effect for living organisms
• (e.g. evaporation of water in sweat, transpiration)

Question 7

What feature of water allows it to have a high shc and slh of vaporisation?

Answer 7

Many hydrogen-bonds.

Question 8

In which processes is water a metabolite?

Answer 8

• condensation
• hydrolysis
• photosynthesis
• respiration

Question 9

What does cohesion between water molecules allow?

Answer 9

• supports transpiration stream in plants
• produces surface tension to support small organisms

Question 10

What does adhesion between water molecules and other molecules allow?

Answer 10

• enables water to move up the xylem as water forms hydrogen bonds with cellulose.

Question 11

Exam Q: Explain 5 properties that make water important for organisms

Answer 11

1. A metabolite in condensation/hydrolysis/ photosynthesis/respiration;
2. A solvent so (metabolic) reactions can occur
   OR
   A solvent so allowing transport of substances;
3. High (specific) heat capacity so buffers changes in temperature;
   For ‘buffer’ accept ‘resist’.
4. Large latent heat of vaporisation so provides a cooling effect (through
   evaporation);
5. Cohesion (between water molecules) so supports columns of water
   (in plants)/ transpiration stream
6. Cohesion (between water molecules) so produces surface tension
   supporting (small) organisms;
   For cohesion accept hydrogen bonding