A-LevelBiologyBiological molecules9700/23 · May/June 2017 · Q65 Marks
In the space below, draw a diagram to show a hydrogen bond between two water molecules.
- (a)In the space below, draw a diagram to show a hydrogen bond between two water molecules.[3]
- (b)(i)Movement of water in xylem depends on the force of attraction between water molecules as a result of hydrogen bonding. State the name given to this force of attraction.[1]
- (b)(ii)State the property of water that results in a cooling effect as water evaporates from the surface of organisms.[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [3] two water molecules drawn with correct bonding; I Fischer projections partial charges shown as σ+ on at least one H and σ– on at least one O; hydrogen bond shown; e.g. labelled or as dashed or dotted lines between H of one molecule and O of another;
- [1] cohesion;
- [1] high / large, latent heat of, vapourisation / evaporation; A takes a large amount of, heat/energy, to evaporate / turn liquid to water vapour
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