Beaker Size & Candle Burning Time Scientific Enquiry Question
The diagram shows a candle burning in air under a bell-jar. You need to plan an investigation to find out if there was a relationship between volume of the container and burning time. You will use 600mL, 400mL, 200mL, 100 mL and 50 mL beakers.
The pupils set up an inverted (upside down) beaker over a candle . They lit the candle and quickly, but 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 Average Burning Time 50 2.1 1.9 2.0 100 4.8 5.1 200 7.3 7.7 7.5 400 12.8 13.0 13.2 600 18.1 17.8 18.7
(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 the 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
Graph of beaker volume versus average burning time for a candle X X Average burning time (s) 0 2 4 6 8 10 12 14 16 18 20 X X 50 100 200 300 400 500 600 Beaker volume (ml)
(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.