Drawing Conclusions
An investigation to find out how the volume of gas produced changes over time.
Magnesium was added to hydrochloric acid. The volume of gas was measured every 30 seconds.
Task
For each of the sections on the graph describe what is happening to the dependent variable as the
independent variable increases. Explain why this is the case.
160
140
Volume of gas (cm3)
120
100
80
60
40
20
0
0
30
60
90
120
150
180
210
240
Time (seconds)
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270
Drawing Conclusions Answers
160
140
2. As time increases, the volume
of gas goes up steadily.
Volume of gas (cm3)
120
3. As time increases, the volume of
gas starts to plateau.
100
80
60
40
1. As time increases, the volume of
gas goes up rapidly.
20
0
0
30
60
90
120
150
180
210
240
270
Time (seconds)
Explain
The volume of gas initially increases rapidly because there is a lot of magnesium and acid to react.
The volume of gas being produced after about 60 seconds rises less rapidly because there is less
magnesium and acid to react together,
The volume of gas starts to plateau because either the magnesium has all reacted and/or the acid has
all reacted.
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