Cambridge IGCSE · Marine Science (0697)

pH and salinity: Practice Questions

5 multiple-choice questions marked as you go, and 5 written questions with worked solutions. All on pH and salinity.

10 questions23 marksFree, no account

Question 1

1 mark

Which of the following substances found in or around the ocean is correctly classified as an element as defined in the syllabus?
A sample of sea water itself is excluded as it is a mixture.

Question 2

1 mark

The Red Sea exhibits a relatively high salinity compared to the Pacific Ocean. Which combination of environmental factors best explains this observation?

Question 3

1 mark

Which of the following describes the effect of increasing the concentration of carbon dioxide (\(CO_{2}\)) in sea water and the resulting change in the universal indicator color?

Question 4

1 mark

What unit is typically used to measure and express the salinity of sea water?

Question 5

1 mark

Why does the Baltic Sea typically exhibit a lower salinity compared to the Pacific Ocean?

Question 6

2 marks

Classify oxygen as an element, compound, or mixture, and provide the chemical formula for the compound calcium carbonate.

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Question 7

3 marks

Explain why the salinity of water within an estuary is not constant and changes during a typical tidal cycle.

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Question 8

5 marks

Describe the opposing effects that an increase in temperature has on the solubility of solid salts (such as sodium chloride) versus dissolved gases in sea water.

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Question 9

3 marks

(a) Define the term salinity and state the standard unit used by marine scientists to express this measurement.
(b) Compare the salinity levels of the Baltic Sea and the Red Sea, and provide one environmental reason for the difference observed in the Baltic Sea.

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Question 10

5 marks

Salinity and pH are two fundamental chemical characteristics of the marine environment.
(a) Define the term salinity and state the units commonly used to express it.
(b) The Red Sea is known for having a high salinity compared to the global average. Suggest and explain two environmental factors that contribute to this high salinity.
(c) Describe the effect of dissolving carbon dioxide from the atmosphere into sea water on the pH of the water.

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