Topic 1.7 - Water Flashcards
2) What does it mean to say that water is a ‘metabolite’?
It means that water is either a reactant or a product in metabolic reactions in living organisms
e.g. it is required for hydrolysis reactions to take place and it is produced in condensation reactions
3) What is a solvent? Why can water act as a solvent? How is this beneficial in terms of chemical
reactions?
● A solvent is a substance in which other substances can dissolve in
● Water is polar, so it can form hydrogen bonds
● This means that polar and ionic substances are able to dissolve in water
(due to the attraction of opposite charges, allowing them to be completely surrounded by the polar
water molecules)
● This is useful because many metabolic reactions occur when substances are dissolved in water.
4) Explain why there is surface tension in water
Because water molecules are polar, so can form H-bonds with other water molecules
This causes cohesion between water molecules, holding them together
(this allows pond skater to walk on water without falling in!)
Explain how the properties of water help water to move up the xylem vessel of a plant
● Water is polar, so it can form hydrogen bonds between other water molecules
● Therefore, there is COHESION between water molecules due to H-bonds
● There is also ADHESION between the water molecules and the wall of the xylem
● Therefore the column of water molecules in the xylem does not break
6) (i) What does it mean that water has a high specific heat capacity?
i) High specific heat capacity means that a lot of energy is required to raise the temperature of water by 1°C
ii) Why does water have a high specific heat capacity?
Because there are lots of Hydrogen bonds between water molecules and they can absorb lots of
energy. OR water can gain / lose a lot of heat / energy without changing temperature;
iii) How is this property beneficial shc
This makes it good at BUFFERING CHANGES IN TEMPERATURE
iv) How is it useful to a) aquatic organisms b) humans?
a) it makes water a good habitat because the temperature underwater is likely to be more stable
than on land (so the temperature changes are not as big)
(b) Water INSIDE organisms remain at a fairly stable temperature therefore helping to maintain a
constant internal body temperature
7) (i) What does it mean when we say that ‘Water has a large latent heat of vaporization’?
(ii) How is this property beneficial to organisms living in hot countries?
(i) (ii)
This means a lot of energy is required to convert liquid water into water vapour
It allows water to provide a cooling effect with little loss of water through evaporation
This is because it takes a lot of energy to break the hydrogen bonds between the water molecules
for evaporation to take place
This is why organisms sweat or cover themselves in mud!
8) Water is a metabolite in many reactions. Which ones do you know of?
Condensation/hydrolysis/photosynthesis/respiration
Give five properties of water that are important in biology. Explain the importance of each property
you identify. [5
- metabolite in condensation/hydrolysis/photosynthesis/respiration
- solvent so metabolic reactions can occur
- high shc so buffers changes in temp
- large latent het of vaporisation so provides a cooling effect
-cohesion between water molecules so supports columns of water
-cohesion so provides surface tension supporting organisms
