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.

 

Problem:  

_______________________________________________________________________

 

Hypothesis (use the form: “If the candle is burned in timed intervals, then it…): _______________________________________________________________________

 

_______________________________________________________________________

 

Materials:


 

·        Hot Mitt or beaker tongs

·        Beaker

·        Beaker of water for extinguished matches

·        Weigh boat

·        Stop Watch


 

 

Procedure:

  1. Create a data table in the data section to record your quantitative data.
  2. Record your observations of the appearance of the unlit candle. 
  3. Using a ruler, measure the height of your birthday candle. Record the initial height.
  4. Place a small lump of clay onto the foil pan. Press the candle into the clay so that it stands securely upright.
  5. Obtain the initial combined mass of the candle, clay and foil pan and record.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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):

  1. Graph the data.  You will produce 2 graphs:  candle height vs time, and candle mass vs time.
  2. For each graph, which variable is the independent variable? Which is the dependent variable?
  3. Using your graphs, estimate how much of both height and mass the candle lost in two minutes.
  4. Calculate the rate of burning in terms of height (mm/min) and mass (g/min) for each 3-minute time interval.
  5. Calculate the average burning rate in terms of both height and mass.
  6. Does the candle burn at a constant rate or does the rate vary?  How do you know this?
  7. Calculate the changes in both height and mass for two minutes.
  8. Calculate how long it would take for the candle to reach a height of 2.5cm.
  9. Calculate how long it would take for the entire candle to completely burn out from start to finish.
  10. Which changes that you observed were physical changes?  Which were chemical changes?
  11. What was the role of the wick in the candle? 
  12. 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):

  1. State your findings. Refer to the problem and your hypothesis.
  2. 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.
  3. Explain the loss of mass of the candle during combustion in terms of the Law of Conservation of Mass.  What are the products of combustion?