water and inorganic ions

Question 1

How hydrogen bonding occurs between water molecules

Answer 1

• Water is a polar molecule
• Slightly negatively charged oxygen atoms attract slightly positively charged hydrogen atoms of other water molecules
• So hydrogen bonds (weak attractive force) form between water molecules

Question 2

properties of water

Answer 2

1. high specific heat capacity
2. high latent heat of evaporation
3. cohesive
4. solvent
5. metabolite

Question 3

high specific heat capacity

Answer 3

• Polar so many H bonds form between water molecules
• These allow water to absorb a relatively large amount of heat energy before its temperature changes

Question 4

what is the importance of high specific heat capacity?

Answer 4

• Good habitat for aquatic organisms e.g. lakes as temperature more stable than land
• Organisms mostly made of water so helps maintain a constant internal body temperature – important as temperature affects enzyme activity

Question 5

high latent heat of evaporation

Answer 5

• Polar so many H bonds form between water molecules
• These can absorb a lot of energy before breaking, when water evaporates

Question 6

what is the importance of high latent heat of evaporation?

Answer 6

• Evaporation of small amount of water (e.g. sweat) is an efficient cooling mechanism
• Helping organisms maintain a constant body temperature

Question 7

cohesive

Answer 7

• Polar so many H bonds form between water molecules
• So water molecules tend to stick together

Question 8

what is the importance of water being cohesive?

Answer 8

• Column of water doesn’t break when pulled up a narrow tube e.g. xylem during transpiration
• Produces surface tension at an air-water surface so invertebrates can walk on water e.g. pond skaters

Question 9

solvent

Answer 9

• Polar (has a slightly positive and negative ends)
• Can separate (dissolve) ionic compounds e.g. NaCl as +ve end attracted to -ve ion (Cl-) and negative end attracted to positive ion (Na+)

Question 10

what is the importance of water being a solvent?

Answer 10

Can dissolve other substances e.g. inorganic ions, enzymes, urea, etc. so water…
- Acts as a medium for metabolic reactions (which
can happen in water)
- Acts as a transport medium e.g. in xylem to
transport nitrates which are needed to make amino acids

Question 11

metabolite

Answer 11

water is reactive

Question 12

what is the importance of water being metabolite?

Answer 12

Condensation releases H2O and forms a chemical bond; hydrolysis requires H2O to break a bond; e.g. amino acids joined by condensation reactions to form polypeptides

Question 13

inorganic ions

Answer 13

• Occur in solution in the cytoplasm and body fluids of organisms
• Some in high concentrations and others in very low concentrations
• Each type of ion has a specific role, depending on its properties and these roles are relevant in a range
  of topics across the A Level