8. Candle Burning Times
Scientific Enquiry Question
The diagram shows a candle burning in air under a
bell-jar.
The class were shown this demonstration, then they
had to plan their own experiment.
They had to find out if there was a relationship
between volume of container and burning time.
The pupils set up a similar
different sizes of beaker. They
lit the candle, carefully put the
beaker over the top of it and
timed how long it took for the
flame to go out. This was
repeated 3 times for each
beaker.
(b) The results from one group
of pupils are given below.
(i) Calculate their average
burning times. Put the
answers in the table
Beaker
volume
(ml)
Burning Times
(secs)
1
2
3
100
4.8
5.1
4.8
200
7.3
7.7
7.5
400
12.8
13.0
13.2
600
18.1
17.8
18.7
Average
Burning
Time
(ii) In this experiment each part of the experiment
was repeated 3 times. Why is it often a good
idea to repeat the readings?
____________________________________
(c) Plot a graph to show group’s results.
The graph must have title that makes it clear
what has been done.
The axes must be labeled to show the
dependent and independent variables.
Any suspect or odd points must be made
clear. (if there are any)
A best-fit line should be drawn.
Attach your graph paper to this sheet
8 10 12 14 16 18 20
6
X
X
X
X
0 2 4
Average burning time (s)
Graph to show how the beaker volume
affects the average burning time of a candle
0
100
200
300
400
500
Beaker volume (ml)
600
(d) Describe the relationship (or pattern) you
can see in the graph.
_____________________________________
_____________________________________
(d) Use the graph to help you answer the next
section of questions.
What burning times would you expect in the
following beakers?
(i) 500 ml ________
(ii) 50 ml _______
(iii) 800 ml ________
(e) Explain why you would be more confident
about the answer you gave for the 500 ml
beakers than the answers for the 50 and 800 ml
beakers.
(f) It looks as if the results were quite reliable
overall and so the strength of evidence for the
conclusion could be fairly strong. However, no
experiment is likely to be perfect. Go back and
look at the diagram and the brief method again.
Point out possible sources of error in this
experiment.