water

Question 1

what are the 4 key properties of water due to the fact it is polar?

Answer 1

• an important solvent
• transport medium
• coolant
• habitat

Question 2

explain how water being a solvent is useful

Answer 2

• because water is polar it is also hydrophillic and can interact with other polar molecules and dissolve them in water.
• the delta positive charge on the hydrogen atoms will attract any negative solutes, or the **delta negative charge* on the oxygen atoms will attract any positive solutes.
• the eukaryotic and prokaryotic cell cytosol is mainly water so many solutes can dissolve within the cell.

Question 3

explain how water being a transport medium is useful

Answer 3

• once dissolved, polar substances can be easily transported in water around plants or animals (blood=animals; xylem, phloem=plants)
• this is due to cohesion: when water molecules stick together because of hydrogen bonding.
• because of cohesion, water can move in a continuous column.
• it is advantageous as it is easier to draw up a stem.

Question 4

explain how water being a coolant is useful

Answer 4

• due to the high SHC of water.
• water has a high SHC because lots of energy is needed to break the hydrogen bonds between water molecules.
• this allows for the internal temperatures of plants and animals to be kept constant.
• this means enzymes dont denature
• water also has a high latent heat of vapourisation > provides a cooling effect in sweat

Question 5

explain how water being a habitat is useful

Answer 5

• because it has a stable temperature, water provides a stable environment
• cohesion provides surface tension to water- allows small invertebrates to live on the surface and hide from predators
• ice is less dense than liquid water (water most dense at 4 degrees) - so ice floats on top of water in winter and provides a surface habitat- or thermal insulation for the water below- for organisms.