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.
Give 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 markGive the name of the interaction between water molecules that determines the properties of water.
2 marksExplain how the properties of cohesion and adhesion are useful to living organisms.
2 marksState two other properties of water that are essential 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 passage below with the correct scientific terms:
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 allows it to aid temperature regulation in humans.
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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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Describe the properties of water that enable 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 the biological importance of this property.
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7 marksFig.1 is a transmission electron micrograph showing two adjacent cells in a leaf.
Fig. 1
(i) 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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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
Describe the results shown in Fig. 1.
2 marksCalculate the percentage decrease in temperature of the covered cup in the first 4 minutes.
2 marksState two control variables for the experiment described in part (a), other than any that have been mentioned in the question above.
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 marksExplain 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 shown in Fig. 1.
3 marksExplain how the properties of water contribute to the cooling effect of transpiration in a leaf.
1 markCalculate the decrease in temperature when the transpiration rate increases from 1 mmol H2O m-2 s-1 to 2 mmol H2O m-2 s-1.
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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 as 104.49°.
Fig. 1
The bond angle that would be expected in a molecule of this shape would usually be larger, around 109°.
Use 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 reaches its maximum density of 1 000 kg m-3 at 4 °C, while the density of ice is 917 kg m-3.
Density can be calculated using the formula:
Density = mass ÷ volume
Use the formula provided to calculate the percentage volume expansion that occurs when 1 000 kg of water freezes from 4 °C to below its freezing point.
State your answer to the nearest whole number.
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