Syllabus Edition
First teaching 2020
Last exams 2024
1 markState the type of chemical bonding that exists within a single water molecule.
2 marksDescribe the change in density of water as it changes to ice.
State an observation that confirms your answer.
1 markFig. 1 shows three water molecules.
Fig.1
On Fig. 1 draw the position of one hydrogen bond, using a dotted line.
2 marksWater is described as a polar molecule
Define the term polar in this context.
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1 markWater is highly important to living organisms.
State the nature of the interaction between water molecules that are used to explain this.
3 marksTwo properties of water are it has cohesive and adhesive forces.
Explain how these properties are useful to living organisms.
1 markBoth water and methane are similarly-sized small molecules containing single covalent bonds between their atoms. Water is a polar molecule whereas methane is non-polar. State one difference between these two molecules that make their physical properties very different.
2 marksList two physical properties, associated with its state of matter, that make water an important molecule for sustaining life.
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1 markDefine the term hydrophilic.
2 marksFig. 1 shows four water molecules (H2O) and a potassium ion (K+).
Fig. 1
Redraw the five molecules in Fig.1 to show how they would arrange themselves in an aqueous solution of potassium salt.
3 marksComplete the missing words in the passage below:
The specific heat capacity of a substance is the amount of ________ required to raise the temperature of _______ of that substance by _________. Water’s specific heat capacity is 4200 J/kg°C
2 marksState and explain the property of water that makes it a good solvent for sweat (perspiration).
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1 markA group of students wanted to investigate the thermal properties of water. They poured hot water into two thin plastic cups and measured the rate of cooling of each cup. The sides of one cup were covered with tissue paper soaked in hot water while the sides of the other cup were left uncovered. The temperature of the water was recorded with a thermometer every two minutes over a 10 minute time period.
The results of this experiment is shown in Fig. 1.
Fig. 1
State the conclusion that the group of students can draw based on the results in Fig. 1.
2 marksCalculate the percentage decrease in temperature of the covered cup in the first 4 minutes.
Show your working.
2 marksState two control variables, other than the starting temperature of the water, for the experiment described in part (a).
4 marksExplain how the experiment in part (a) can demonstrate how humans respond to overheating, with reference to the thermal properties of water.
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4 marksDescribe the properties of water that make it a useful component of blood.
2 marksA group of scientists investigated the cooling effect of transpiration on the surface temperature of leaves from the species Eucalyptus saligna.
Fig. 1 shows their results.
Fig. 1
Describe the results from their investigation.
3 marksExplain how the properties of water contribute to the cooling effect of transpiration in a leaf.
2 marksCalculate the decrease in temperature when the transpiration rate increases from 1 mmol H2O m-2s-1 to 2 mmol H2O m-2s-1.
Show your working.
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2 marksSuggest and explain one advantage to ecosystems of solid water (ice) being less dense than liquid water.
2 marksFig. 1 shows a water molecule with its bond angle labelled at a value of 104.49°.
Fig. 1
The bond angle that would be expected in a molecule of this shape would be larger, around 109°.
Use the information in Fig. 1 to suggest why water's bond angle is less than that of the expected geometric shape of a water molecule.
3 marksWater differs from most liquids in that it becomes less dense as it freezes. It reaches its maximum density of 1 000 kg m-3 at 4°C.
The density of ice is 917 kg m-3
Calculate the percentage volume expansion as 1 000kg of water freezes from 4°C to below its freezing point.
State your answer to the nearest whole percentage.
2 marksThe lower density of ice allows ice caps to form above liquid water.
Ice has insulating properties.
Explain one advantage of this to aquatic life.
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Water is a very important component of cells and performs a variety of functions within living organisms.
Explain the role of water within a cell.
Fig.1 shows a diagram of three water molecules.
Fig. 1
Identify Y in Fig.1 and describe how it forms.
Contrast covalent bonds and hydrogen bonds with one another.
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Discuss the properties of water that enables it to dissolve solutes.
Explain, with reference to bonding, how the relatively high specific heat capacity of water enables it to buffer temperature changes.
Explain the importance of the high latent heat of vaporisation of water to living organisms.
The relatively high specific heat capacity of water is of great biological significance to organisms. Give one example of how this property is biologically important.
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7 marksFig.1 is a transmission electron micrograph showing two adjacent cells in a leaf.
Fig. 1
Cellulose is the main polysaccharide in cell walls of plants.
Describe the structure of cellulose.
[3]
ii)
State one feature visible in Fig. 1, other than the cell wall, that identifies the cells as plant cells.
[1]
iii)
Outline the role of ATP in a leaf cell.
[3]
2 marksWater is a main component of plant cells.
Fig. 2 shows two water molecules linked by a hydrogen bond.
Fig. 2
Explain how hydrogen bonding occurs between water molecules.
2 marksSuggest why water is an excellent solvent for ions.
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