Burning of a Candle Lab
Background: Combustion is a chemical
reaction in which a substance is combined with oxygen. This reaction gives
off energy in the form of heat and light. In this investigation the substance
that is combining with the oxygen is candle wax. You will observe the burning
of a candle and measure the rate at which a candle burns.
Purpose: To observe the burning of a candle
and to determine the rate at which a candle burns.
Hypothesis (use the form: “If the candle is
burned in timed intervals, then it…):
- Safety goggles
- Large Birthday candle
- Ruler, 30 cm
- Small lump of clay
Hot Mitt or beaker tongs
Beaker of water for extinguished matches
- Create a data table in the data section to record your
- Record your observations of the appearance of the unlit
- Using a ruler, measure the height of your birthday
candle. Record the initial height.
- Place a small lump of clay onto the foil pan. Press the
candle into the clay so that it stands securely upright.
- Obtain the initial combined mass of the candle, clay and
foil pan and record.
- Carefully light the candle with a match and allow it to
burn for 2 minutes. Then blow out the candle, and obtain the
combined mass of the candle, clay and foil pan. Carefully remove the candle
from the clay and measure its length. Safety note: After lighting the
candle, blow out your match and then place it in the beaker of water to cool.
- While the candle is burning, record your observations of
the flame and candle, observing what is burning, where the burning is taking
place, and where the most heat is released.
- Repeat step 4 four more times, for
a total burning time of 10 minutes. Each time you should secure
the candle in the clay before lighting, measure the combined mass of the
candle, clay and foil after burning, and then remove it from the clay to
measure its length.
- Relight the candle and place a beaker upside down over
the candle. Record your observations of the candle flame and the interior of
the beaker, and record the time it takes for the candle to be extinguished.
Use a glove to remove the beaker.
- When you are finished, place the extinguished candle in
the beaker. DO NOT put any matches or candles on your tables or in the
sink – they should all be placed in the beaker, and put into the trash at the
end of the lab.
Analysis (show all calculations):
- Graph the data. You will produce 2
graphs: candle height vs time, and candle mass vs time.
- For each graph, which variable is the independent
variable? Which is the dependent variable?
- Using your graphs, estimate how
much of both height and mass the candle lost in two minutes.
- Calculate the rate of burning in
terms of height (mm/min) and mass (g/min) for each 3-minute time
- Calculate the average
burning rate in terms of both height and mass.
- Does the candle burn at a constant rate or does the rate
vary? How do you know this?
- Calculate the changes in both
height and mass for two minutes.
- Calculate how long it would take
for the candle to reach a height of 2.5cm.
- Calculate how long it would take
for the entire candle to completely burn out from start to finish.
- Which changes that you observed were physical changes?
Which were chemical changes?
- What was the role of the wick in the candle?
- Why does the flame diminish when the burning candle is
covered with a beaker? What do you think the substances are that formed
inside the beaker?
Conclusion (Please answer the questions in
complete sentences as your conclusion paragraph):
- State your findings. Refer to the problem and your
- Hypothesize how the rate of burning a tall thin birthday
candle might compare to that of the traditional birthday candle that was used
in your experiment. Be sure to give reason(s) for your hypothesis.
- Explain the loss of mass of the candle during combustion
in terms of the Law of Conservation of Mass. What are the products of