MODULE 2 : water

Question 1

Functions of water

Answer 1

reactant
solvent
medium of transport
coolant 
habitat

Question 2

why is water useful as a solvent?

Answer 2

• as water is polar (partial positive and negative charge) many ions and covalently bonded polar substances will dissolve in it
• this is because ions and polar substances have negative and positive parts to their structure
• the negative parts of the substance will be attracted to the hydrogen atoms and the positive parts of the substance will be attracted to the oxygen atoms

Question 3

why is water useful as a reactant?

Answer 3

water is an ideal reactant and reaction medium as the cytoplasm is an aqueous solution which means that substances can be dissolved and reaction can take place

Question 4

water and high specific heat capacity

Answer 4

• water has a specific heat capacity of 4200 j/kg which means a lot of energy is required to raise its temperature
• the capacity is high bcs hydrogen bonds require lots of thermal energy to break down and this is useful bcs the temperature of water will not fluctuate greatly
• this is useful as water can be a suitable habitat due to its constant temperation

Question 5

water and latent heat

Answer 5

• water has high latent heat of vaporisation which means its harder for it to change state
• this is an advantage for organism as only a small amount of water is required to evaporate for the organism to lose heat
• this provides a cooling effect e.g. sweat on skin

Question 6

cohesion

Answer 6

when water molecules stick to each other

- water molecules are very cohesive bcs they’re polar this helps water to follow and transport substances

Question 7

adhesion

Answer 7

when water molecules stick to other substances

- water being adhesive allows it move up the xylem during transpiration

Question 8

hydrogen bonding

Answer 8

check back of textbook

Question 9

hydrophilic

Answer 9

materials with an attraction for water molecules and are generally water soluble

Question 10

hydrophobe

Answer 10

materials that repel water causing droplets to form and are not water soluble

Question 11

how is water polar?

Answer 11

• water as a whole is electrically neutral but the sharing of electrons is uneven between oxygen and hydrogen atoms
• oxygen atoms attract electrons more than the hydrogen atoms so the other side of each hydrogen atom is left with a partially positive charge

Question 12

delta positive

Answer 12

• hydrogen atoms are delta positive which means that they are partially positive

Question 13

delta negative

Answer 13

• oxygen atoms are delta negative which means that they are partially negative