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Control variables in a kettle investigation
A student investigated how the mass of water in an electric kettle affected the time taken for the water to reach boiling point. The kettle switched off when the water reached boiling point.
Give one variable that the student should have controlled.
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Marking points
- 1 Give the starting temperature of the water as a controlled variable, or the starting temperature of the kettle.
Full-mark answer
The starting temperature of the water should have been controlled.
Why this answer loses marks
The mass of water.
The mass of water was the independent variable being changed, so it should not be given as the controlled variable.