Carbon dioxide and global warming: the greenhouse effect
4 marks · NormalA student performs an experiment by heating copper(II) carbonate in a test tube over a Bunsen burner.
State the initial colour of copper(II) carbonate.
Describe the change in appearance during heating.
Name the gas released and describe a test to confirm its identity.
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(a) Green
(b) It turns black (forming copper(II) oxide).
(c) Carbon dioxide. Bubble the gas through limewater; it turns cloudy.
Common mistakes: Saying 'blue' instead of 'green' for initial colour; Not mentioning limewater test
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Marking points
A1 (a) · 1 mark · Initial colour stated as green.
B1 (b) · 1 mark · Describes the powder turning black during heating.
M1 (c) · 1 mark · Names the gas as carbon dioxide.
M2 (c) · 1 mark · States the limewater test and correct result.
Worked solution
a) The initial colour is green.
b) It turns black as copper(II) oxide is formed.
c) The gas is carbon dioxide. If bubbled through limewater, the limewater turns cloudy, confirming CO2.