A1.1 Water

Question 1

Water as the medium of life

Answer 1

First cells originated in water (hydrothermal vents), water remains the medium of life because its where most processes of life (chemical reactions) occur

Question 2

What is cohesion?

Answer 2

Hydrogen bonds WITHIN water molecules
Allows column of water to move under tension (mass transport) through xylem in plants
Surface tension: hydrogen bonds occur on top layer of water creating film, pond skaters use as habitat

Question 3

Why do hydrogen bonds between water molecules occur?

Answer 3

Polarity of covalent bonding within water molecules is due to unequal sharing of electrons.
Therefore hydrogen bonds between water molecules occur.

Question 4

What is adhesion?

Answer 4

Hydrogen bonds TO OTHER MOLECULES which are polar or charged.
Also enables mass transport in xylem + cellulose fibres in cell walls during transpiration
Capillary action: water drawn up narrow channels (capillary tubes) in soil

Question 5

How do different type of molecules react to making hydrogen bonds with water?

Answer 5

Polar molecules + pos or neg charged molecules: hydrophilic, can form hydrogen bonds with water
Non-polar molecules, no charge: hydrophobic, cannot form hydrogen bonds with water