Reactions of metals with water
3 marks · EasyPotassium reacts vigorously when added to a trough of cold water.
Describe two observations you would make during this reaction.
Name the gas produced in this reaction.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) — · must show Fizzing, Lilac flame, Potassium moves on surface, Melts into a ball, Hissing sound
(b) Hydrogen · must show Hydrogen
Common mistakes: Omitting flame or explosion; naming oxygen as the gas produced.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States one correct observation: e.g. 'The potassium moves rapidly across the surface' or 'bubbles of gas are produced.'
B2 (a) · 1 mark · States a different valid observation: e.g. 'A lilac flame is seen' or 'the potassium melts into a ball.'
B1 (b) · 1 mark · Names the gas produced as hydrogen.
Worked solution
a) Two possible observations:
- The potassium moves quickly on the surface of the water.
- A lilac-coloured flame appears.
b) The gas produced is hydrogen.