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Chemistry in Context - The Burning Candle Lab
Introduction
Why does a flame burn? This lab will test your skill at observation as you investigate the seemingly
simple process of a candle burning.
Observation is an important part of science but is often misunderstood by beginners. Many
students believe that “observing” is the same as “seeing”. However, observing is much more than
seeing.
For example, at the scene of an accident different witnesses will often give different testimony
as to what they saw. The witnesses all saw the same thing, but some are more observant than
others.
This lab consists of a simple system--a burning candle. You have undoubtedly seen a burning candle
many times before. In this lab, you will observe the candle, and then make inferences based on what
was observed. You must make a minimum of 40 observations total and an inference for EACH part of
the lab. Remember that an inference is your conclusion based on the basis of evidence and reasoning.
Pre-laboratory Assignment
Read the ENTIRE lab procedure and then answer the pre-lab questions.
1. How many diff erent sets of observations and inferences are you to make of the burning
candle?
2. What is the purpose of the 250 mL beaker in Part 3?
3. What is the purpose of the 250 mL beaker in Part 4?
4. In Part 5, how far away from the wick are you to hold the burning splint after the candle
is blown out.
5. List the materials needed for Part 8.
6. Why is it important to hold the thermometer in the center of the water in the testtube
when recording temperature?
7. How many total observations must you make? How many inferences?
Unit 1A. Burning Candle Lab
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Materials
1 candle
Matches
Limewater
250-ml beaker
Test-tube
600 mL beaker
Thermometer
1000 mL beaker
Test tube holder
Wire gauze
Graduated cylinder-10 or 25 mL
Cobalt chloride paper
Wooden splint
Erlenmeyer flask (150 or 250 mL)
Safety: Tie back hair and loose clothing. Do not drop matches into the sink.
Procedure and Observations
Part 1. Teacher demonstrations
a. Your teacher will demonstrate a combustion reaction using a flammable liquid.
i.
What is the fuel?
ii. Write down 3 observations about the fuel BEFORE the demonstration?
iii. Write down 5 observations DURING/AFTER the demonsration?
FOR PARTS 2-9, Write an Analysis/Inference statement after EACH SET OF OBSERVATIONS.
ANALYSIS: What is your inference(What conclusion can you draw) about the candle based
ONLY on the observations made for that part.
Procedure
1.
2.
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Unit 1A. Burning Candle Lab
Observations / Data
1.
2.
3.
4.
5.
38.
39.
40.
Analysis / Interpretation
1.
2
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2
Part 2. The unlit/burning candle
a. Observe the UNLIT candle and record as many observations as you can.
b. Light the candle and observe the burning candle. Record as many observations as you can
during the next 5 minutes. Observe and record what happens when you put out the candle (to
avoid blowing wax all over, cup you hand behind the candle when you blow it out). Use all your
senses! Be sure to notice how many states of matter are present while the candle is burning.
Part 3. The 250-mL beaker
a. Lower a clean, dry 250-ml beaker, right side up, into the candle flame,
and hold it there for a moment. The candle flame should just touch
the bottom of the beaker, without letting the flame go out.
b. Record your observations:
Part 4. The upside-down 250-mL beaker
a. Hold a clean, dry 250-ml beaker upside down over the burning candle.
b. Locate the flame just inside the mouth of the beaker so that it will
continue to burn. Hold the beaker at this height for a few seconds, and
note the appearance of the material, which collects on the sides of the
beaker.
c. Wipe a piece of cobalt chloride paper over the material collected on the sides
of te beaker. (Cobalt chloride paper turns pink in the presence of water)
d. Record your observations:
Part 5. The smoldering splint
a. Light the candle, and allow it to burn for 1 minute.
b. Hold a wood splint in the candle until it catches on fire, then hold the
burning splint away from the candle.
c. Blow out the candle with a short puff of breath and immediately hold the
burning splint about 2” from the wick in the smoke rising from the candle.
d. Record your observations:
Unit 1A. Burning Candle Lab
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Part 6. The Wire Mesh (wire gauze)
a. Burn your candle for 1 minute.
b. Take the square of wire mesh (wire gauze) and Slowly lower a portion of the mesh with
holes, not the solid center of the mesh, down over the wick and flame of your candle.
c. Slowly raise the mesh up and down in the flame.
d. Record your observations:
Part 7. 1000 mL vs. 600 mL beaker
a. Turn a 1000 mL beaker over the lit candle. Record the time required for the flame to extinguish.
b. Re-light the candle. Turn a 600 mL beaker over the lit candle. Record the time required for the
flame to extinguish.
Part 8. Limewater test
a. Obtain about 10 mL of limewater in a graduated cylinder. Be careful not to agitate the limewater
prematurely.
b. Invert an Erlenmeyer flask slightly over the flame for 45-60 seconds so that the gases being
produced are collected in the flask. Then lower the flask over the burning candle until the flame is
extinguished.
c. QUICKLY Remove the flask, turn it upright and add limewater to the flask.
d. Stopper the flask, shake the solution and watch for a change in the solution. (Limewater turns
cloudy in the presence of carbon dioxide gas)
e. Record your observations
Part 9. Temperature Test
a. Half fill the test tube with tap water.
b. Check the temperature of water and record.
c. Heat the water over the candle for about 2 minutes. Make sure to use a test tube clamp to avoid
burning yourself.
d. Record the temperature every 30 seconds. Make sure to hold the thermometer in the middle of
the water.
Unit 1A. Burning Candle Lab
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Cleaning Up
a. Wash all dirty glassware.
b. Return all CL EAN an d DRY materials t o ap pr opr i at e s t or ag e l o c at i on .
c. Wipe down your lab bench.
Analysis and Conclusions
a. Name four things (substances/materials) a burning candle produces. What is the proof that
these substances are produced. Use your lab, cite specific test/part.
b. When the candle is lit, what is the main fuel, the wax or the wick? Support your
answer with observations.
c. When the candle is lit, what state of matter (solid, liquid, or gas) do you think is
actually burning? Explain. Hint: answer these questions. What happens when you try
to light the bottom of a candle? What happens when you heat a liquid? .
d. Develop a hypothesis that explains what happened when you placed the burning splint
in the smoke. Hint: What are the three ingredients you need for a fire? What is
the fuel in a burning candle? What state of matter is the fuel?
e. Develop a hypothesis that explains what happened when you placed the wire mesh over
the flame. Hint: what happened to the temperature of the copper wire? What
happened to the fuel for the burning candle?
f. List at least 7 questions that you have as a result of doing this lab. These should be
related to the lab and observations you made that perhaps you don’t fully understand.
g. CONCLUSION STATEMENT: Write a 1 paragraph conclusion statement that should
include the following: a statement about the purpose of the lab; a statement about what
you can conclude from the lab; if the results of the lab were valid, explain why, based on
your data. If the results were not valid, explain why the data shows that the results were
incorrect and explain what you could have done better. Include three specific sources of
error and discuss how they affected your results, what you could do to avoid a similar
error in the future.
Unit 1A. Burning Candle Lab
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