Work by Ben, Alyssa and Emma
Report by Emma

April 4, 2011

Purpose:
To test the claim that as a candle burns oxygen within a test tube, the building level of carbon dioxide smothers the flame.

Materials:
Matches
4 Candles (of significantly different heights) marked 1, 2, 3 and 4
Flip camera
Stopwatch graduated in 0.01 s
4 beakers (of different volumes: one of approximately 11 cm3, one of approximately 30cm3, one of approximately 46cm3, one of approximately 79cm^3) and marked 1, 2, 3, 4, respectively
9” Pyrex pie plate
Water
Ruler graduated in mm
Microsoft Excel

Procedure:
To start the experiment, the heights of four different candles are measured and recorded. Next, the bottom of candle one is melted so that it sticks to the pie plate. The dish is then filled with a specified amount of water, and the candle is lit with a match. A jar is placed over the candle. The water in the dish covers the edge of the jar, insuring that the air cannot leak out. The time it takes for the candle to go out (from the time the jar is placed over the candle) is recorded by both the video camera and the stopwatch. With these same materials, the process is repeated three times. After three times are recorded, candle one is replaced with candle two, and the process is repeated (the jar volume stays the same- they only variable is the height of the candle). After three times are recorded with candle two, the process repeats with candles three and four. Once all tests are completed, the data is entered into Microsoft Excel, and graphed.

To begin the next set of experiments, the bottom of one candle is melted so that it sticks to the pie plate (note that this candle will be used for all four trials, so the height is now a constant). The plate is then filled with a specified amount of water, and the candle is lit with a match. The first of the our different beakers of different volumes is placed over the candle. The water dish covers the edge of the jar, insuring that the air cannot leak out. The time it takes for the candle to go out (from the time the jar is placed over the candle) is recorded by both the video camera and the stopwatch. This process is repeated two more times. After three times are recoded, jar one is replaced with jar two, and the process is repeated. After three times are recorded with jar two, the process repeats with jars three and four. Once all tests are completed, the data is entered in Microsoft Excel, and graphed.

Data and Analysis:
Height of Candle (in)
Test 1 (sec)
Test 2 (sec)
Test 3 (sec)
4.19
18.0
13.6
14.0
3.56
16.0
29.0
23.7
2.94
23.2
22.0
24.0
2.50
22.3
24.0
17.9

Height of Candle (in)
Average Burn Time (sec)
4.19
15.2
3.56
22.9
2.94
23.1
2.50
21.4


?
Volume of Jar (cm^3)
Test 1 (sec)
Test 2 (sec)
Test 3 (sec)
11.3515
2
4.4
1.5
30.0415
16
15.9
13
45.7004
21
22.1
21
78.5398
37.8
35.2
37.8

Volume of Jar (cm^3)
Average Burn Time (sec)
11.3515
2.63
30.0415
14.97
45.7004
21.37
78.5398
36.93


As seen in Figure 1, the results of our first experiment were inconclusive at best. There was no direct correlation between the height of the candle and the amount of time it took the candle to go out. NOTE: There was a pattern in that the tallest candle went out first, then the shortest, then the second tallest, and then the second shortest, but this did not produce a linear correlation (more of a bell curve).
The second set of tests produced very convincing data. As seen in Figure 2, there was a direct correlation between the volume of the jar, and the amount of time it took for the candle to go out.

From this data, it can be concluded that the candle went out because of the reduced oxygen in the jar, and not because it was smothered by carbon dioxide. This is evidenced by the direct correlation between the volume of the jar and the burn time of the candle.

Uncertainty Analysis:
Possible causes for altering the data:
- Heating of jar (would decrease the amount of oxygen in the jar because it expands)
- Condensation (water) on side of jars (could provide the candle with more oxygen)
- Amount of water in dish (see above)
- Height of candle changes slightly after burning (probably minimal because burns for such a short period of time, but still something to keep in mind)

(Edit by Jonathan: Later analysis made clear that these factors were insignificant.)

Conclusion:
The candle goes out because of the reduced oxygen in the jar, and not because it is smothered by carbon dioxide.