Syllabus Edition

First teaching 2023

First exams 2025

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Water (SL IB Biology)

Exam Questions

2 hours21 questions
1a
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1 mark

Define the term 'hydrophilic'.

1b
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3 marks

Two of the properties of water are its cohesive and adhesive forces.

Describe how these properties are useful to living organisms.

1c
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2 marks

Both water and methane are small molecules containing single covalent bonds between their atoms. 

State two differences between these two molecules that make their physical properties very different.

1d
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2 marks

List two physical properties, associated with their state of matter, that differ between water and methane.

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2a
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7 marks

Describe the properties of water molecules that enable them to transport metabolites, using four named examples.

2b
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1 mark

The image below shows a meniscus formed by water inside a glass tube. 

Name the property of water that allows its molecules to form a meniscus like this one, as the water makes contact with the inner surface of a glass container.

meniscus-in-glass

User:Thirunavukkarasye-Raveendran, CC0, via Wikimedia Commons

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1a1 mark

Which property or properties (A, B, C) explain the ability of water to dissolve solutes?

       Property A:    Polarity of water molecules

      Property B:    High specific heat capacity of water

      Property C:    Hydrogen bonding   

1b3 marks

Describe the properties of carbon that make it an ideal element as the basis of living systems. 

1c2 marks

A group of students investigated the thermal properties of water. To do this, they poured hot water at 70°C 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. The sides of the other cup were left uncovered. The temperature of the water in each cup was recorded with a thermometer every 2 minutes for 10 minutes. The results are shown in the graph below.

 q1c-2-1-metabolism-water-medium-ib-hl-biology-sq

Other than the starting temperature of the water (70°C), give two conditions that must be kept the same for each cup throughout the experiment.

1d2 marks

With reference to a thermal property of water, explain how the experiment in part c) can demonstrate the response of the human body to prevent overheating.

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2a2 marks

Water plays a very important role within the cytoplasm of cells. Two properties of water that make it an important part of the cytoplasm of cells are its polarity and its ability to act as a universal solvent.

For each of these two properties, explain why this makes water important for the cytoplasm.

2b1 mark

The relatively high specific heat capacity of water is of great biological significance to organisms.

State one example of how this property is biologically important.

2c2 marks

With reference to bonding, explain how the relatively high specific heat capacity of water enables it to buffer temperature changes.

2d3 marks

The diagram below shows three water molecules in close proximity to each other. Using a dotted line, draw a hydrogen bond between water molecules. Also use the symbols δ+ and δ- to indicate small electrostatic charges on the appropriate atoms.2twmhYny_q2d-2-1-metabolism-water-medium-ib-hl-biology-sq

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3a3 marks

Compare and contrast the terms adhesion and cohesion in the context of water molecules in biological tissues. 

3b3 marks

The diagram shows a pond skater (or water strider).q4b-2-1-metabolism-water-medium-ib-hl-biology-sq

Certain small animals such as pond skaters and fisher spiders can walk across bodies of water without breaking the surface.

Use your knowledge of water's properties to suggest how detergent pollution contaminating ponds and lakes can have a detrimental effect on these small animals.

3c2 marks

Outline how vasodilation affects the volume of water lost as sweat in humans.

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4a7 marks

One mark is available for clarity of communication throughout this question.

Explain the importance of hydrogen bonding in biological molecules.

4b4 marks

Explain how certain biological molecules are hydrophilic, some are hydrophobic and others are amphipathic. Use named molecules as examples in your answer. 

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1a
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2 marks

Eastern collared lizards and pigs are two examples of animals that pant to keep cool.

Suggest how panting helps these animals to cool down.

1b
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3 marks

Draw a labelled diagram showing cohesive forces between three water molecules.

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2a
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2 marks

Outline the significance of the surface tension of water to living organisms.

2b
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2 marks

Using your knowledge of the properties of water, explain why dilute aqueous solutions (eg. glucose solution) are clear. 

2c
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2 marks

Explain the relationship between the solute concentration of a solution and its water potential. 

2d
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2 marks

Explain how water's high specific heat capacity helps to keep environmental conditions constant for organisms.

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3
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6 marks

Water exists in all three of its physical states in Nature.

Give an example of each physical state of water that exists in Nature and how it affects organisms and ecosystems.

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4a
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4 marks

One mark is available for clarity of communication throughout this question.

Deamination (the removal of an amino group from a molecule) and gluconeogenesis (the production of glucose from non-carbohydrate sources) are two reactions that occur in the liver.

From the information given, suggest with reasons, which metabolic reactions these are classified as.

4b
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8 marks

Explain the properties of water that are key for the survival of an oak tree.

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