burning candle experiment data

A study of the rate of a candle burning

Michael P Jansen, Crescent School, Toronto, Ontario

Introduction

In this investigation, students will study the rate of burning of a candle as a function of the mass of the candle and as a function of the concentration, or partial pressure of O 2 (g).

Candle wax is a hydrocarbon (ca C 25 H 52 ). It combusts according to:

wax(s)  +  O 2 (g)  → CO 2 (g)  +  HOH(g)     (Equation 1)

(Wax burns as a vapour, but we indicate it as a solid; the mass of the solid is measured here.)  

The rate law equation for this reaction is:

rate  =  k(solid wax) x [O 2 ] y     (Equation 2)

In our lab we will burn the candle in air, in which [O 2 ] is constant. Therefore, equation 2 becomes

rate  =  k observed (solid wax) x , where  k observed = k[O 2 ] y = constant    (Equation 3)

Typical values for x are 0, 1 or 2, but higher integer values and even fractions are possible.

If x = 0, the reaction is zero-order with respect to the wax; If x = 1, the reaction is first-order with respect to the wax; If x = 2, the reaction is second-order with respect to the wax… you get the idea.

Later in this investigation students examine data for the combustion of a candle at increasing elevations above sea level, where the concentration (or partial pressure) of O 2 (g) is lower. This will allow students to determine the value of the exponent “y”.

To determine the rate of the reaction and the reaction order of wax(s) and of O 2 (g) using the equation  rate  =  k[wax] x [O 2 ] y .

• small candle, such as a tea light
• small beaker
• electronic balance
• timing device

Safety precautions

Wear safety glasses; tie back hair and loose clothing. Make sure matches are extinguished before putting them in the garbage — not the sink.

Pre-lab questions or class discussion

• a) How do you expect that the rate of burning will vary with the mass (or length) of the candle?  b) Based on your prediction in part (a) sketch the following graphs:mass of wax (y-axis) versus time (x-axis); burning rate (mass of wax per second) versus time.

Part 1.  Determination of “x”

• Read the procedure and analysis questions before you begin. Use prepare a data table in which you record your findings and put calculated data. Place a heading at the top of each column. 
• Place the tea light on an inverted small beaker. Ignite the candle, letting it burn for about two minutes in order to melt the wax near the wick. 
• Start your timer and immediately record the mass of the candle. Record the mass of the candle every 60 s for at least five minutes.

Determination of “x”  (Order of reaction with respect to solid wax)

• a) Plot a graph of mass of candle versus time. Use spreadsheet  software to determine the equation of the line of best fit and the corresponding R 2 value.
• b) Plot a graph of [∆mass•time –1 in g•s –1 ] of the candle on the y-axis, versus time on the x-axis. 
• a) Comment on the shape of your graphs. That is, are they linear/horizontal/vertical/parabolic/etc? b) Do your experimental results support your prediction? Explain    briefly.
• What is the order of the reaction (the value of “x”) with respect to  solid wax?

Sample results

Part 2.  Determination of “y” (Order of reaction with respect to [O 2 ])

4.  To determine how the partial pressure, which is related to concentration of O 2 (g) in the air, affects the rate of combustion of a candle, use the data below to plot a graph of combustion rate (g•min –1 ) versus PPO 2 — use spreadsheet software. The data were obtained by Crescent School students on the slopes of Mount Kilimanjaro (outreach trips to Tanzania). They burned candles at increasing elevations above sea level. (Since air is 21% O 2 by volume and by pressure, the partial pressure of O 2 can be obtained by multiplying the atmospheric pressure (P atm ) by 0.21.)

The following table has the combustion rate of a candle at increasing elevation above sea level. Partial pressure of O 2 can be calculated and filled in.

5. What measurements did the students who obtained these data record? 

6. Plot a graph of rate of wax combustion (y-axis) versus PPO 2 . From your graph determine as quantitatively as possible, the effect of the PPO 2 on reaction rate. 

7. What is the order of the reaction with respect to PPO 2 ?

8. Rewrite Equation 2 with suitable values for the exponents.  

Toronto, Canada is at 76 m, typically around 102 kPa. In this analysis we assumed that the temperature of the burning candle is the same at the different altitudes. If this is not the case, our rate data collected on the mountain slope would reflect both the effect of a (presumably) decreasing flame temperature and the decreasing partial pressure of oxygen.      

More about February 2019

Department of Chemistry 200 University Ave. W Waterloo, Ontario, Canada N2L 3G1

[email protected]

Getting the facts right

Photos of the experiment

An exhibit of explanations

What do we learn, appendix: the chemical equation for general n.

Appendix: the ideal gas equation

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The chemistry of candles

By Stephen Ashworth 2015-05-01T08:38:00+01:00

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Stephen Ashworth explains why the chemistry of the candle is not as simple as it might seem in this article from the ‘Avogadro’s lab’ series

Source: © Shutterstock

Small candles or ‘tealights’

Have you ever used chemistry to make light? You probably have, but might not have thought of it as chemistry. Before electric light was commonplace, all artificial light was produced using chemistry. Light is often the result of combustion or heating, or both. A simple fire produces light because the sticks or coals get sufficiently hot to glow red – red hot. Gas was widely used for streetlights and in the home, but a gas flame itself does not produce much illumination. It was found, however, that heating a substance such as lime (hence the term ‘in the limelight’) or a mantle impregnated with thorium produced a brilliant white light. This principle is still used in mobile lighting and gas lamps used for camping, although thorium has generally been replaced by other elements such as yttrium, zirconium and cerium.

Did you know?

Scientists at NASA have been experimenting with flames on the International Space Station. Watch  this video to see the strange, cool-burning form of fire they have discovered.

Scientists at NASA have been experimenting with flames on the International Space Station. Watch this video to see the strange, cool-burning form of fire they have discovered (http://bit.ly/1bCFOhB).

Michael Faraday

The title page to the first edition of The Chemical History of a Candle (1861) by Michael Faraday

A convenient source of chemical illumination is the humble candle. The candle was the centrepiece of one of the most famous series of popular science lectures. The six Christmas lectures delivered by Michael Faraday at the Royal Institution in December 1860 and January 1861 were on The Chemical History of a Candle . Circumstances conspired to force Faraday to recycle some material from earlier Christmas lectures, yet these form a coherent whole and the book based upon the lectures has not been out of print since its first publication in March 1861.

Over the course of the lectures Faraday demonstrated to his audiences of around 700 many aspects of the chemistry relating to candles. Starting with how candles can be produced, he ranged far and wide and covered, using deceptively simple experiments, chemical themes including the composition of the gases produced on burning and the structure of the flame itself

The shape of the flame

In a burning candle, wax is drawn up the wick by capillary action and evaporates, so what is burned is a gas. The heat of the flame produces an updraught of air that draws the flame into its familiar shape. In zero gravity there is no ‘up’ and a flame forms a sphere. In both cases, the fuel only burns in the region where the mixture of oxygen and fuel is correct.

We can test this in several ways. First, read thoroughly the safety information below. Then take a sheet of paper and hold it in the candle flame a short distance above the end of the wick such that it burns but does not ignite. The mark should appear as a circle, showing the flame is hollow. You may need a few attempts to see this. To show it is not liquid wax that burns, simply blow out the candle and before it cools too much bring another flame to the wick from above. The candle flame will reignite before the other flame touches the wick – it is the remaining cloud of gaseous wax is what burns. A piece of cold metal held in the flame for a short time will collect soot from the flame but also small droplets of condensed wax.

These and many other simple, yet extremely effective, experiments that revolve around the chemistry of a candle are part of the series of lectures. These, and a commentary, are included in a new edition of Faraday’s book .

These and many other simple, yet extremely effective, experiments that revolve around the chemistry of a candle are part of the series of lectures. These, and a commentary, are included in a new edition of Faraday’s book (http://bit.ly/1Fxt7yS).

• Make sure an adult knows what you are doing.
• Take care with flames and hot wax, these can burn skin. Place burnt skin under cold water immediately and keep it there for several minutes.
• Tie long hair back and keep hair and loose clothes away from the flame.
• Use a metal baking tray or something similar to catch burning paper or liquid wax.
• Do not hold the candle in your hand. Use a candle holder. Plasticine or Blu-Tack can stick the candle in place, or use a tea light.
• Do not leave burning candles unattended.

Additional information

This article originally appeared in The Mole , the student magazine published by the Royal Society of Chemistry from 2012 to 2015.

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Science in School

A twist on the candle mystery teach article.

Author(s): Steven Ka Kit Yu

Three candles of different heights are lit in a closed space. Surprisingly, the longest candle goes out first. Can you solve the mystery?

In a classic demonstration of the candle mystery, three lit candles of different heights are covered with a gas jar (see figure 1) and the tallest candle goes out first. This happens because carbon dioxide produced from burning has a higher temperature, so it rises and accumulates at the top of the jar. Then the carbon dioxide gas cools down, falls, and extinguishes the tallest candle first. This article builds on the classic demonstration of the candle mystery and advances it in three ways. Firstly, the 5E instructional model [ 1 ] is used to develop learning activities that require students to construct, revise, and apply scientific explanations in unpredictable contexts. Secondly, these activities aim to help students test their hypotheses by using and coordinating multiple pieces of evidence. Thirdly, these activities include experiments and discussion tasks to challenge students to predict and explain results. By adding variables to the candle mystery, you can engage students and promote critical thinking and scientific understanding.

The experiments can be conducted as demonstrations or as hands-on practical work for small groups of students. They are quick and easy. The activities can be used with students aged 11 to 16.

Safety notes

• Follow all fire safety regulations and have fire extinguishing materials on hand.
• Wear safety goggles throughout the experiments. If students are performing any steps themselves, they should do the same and be warned to take care around open flames.
• The gas jar can become very hot during and immediately after candles are extinguished. Students should be warned not to touch it with bare hands and care should be taken (e.g., wear heat-resistant gloves when lifting the hot gas jar and/or lift the gas jar when it has cooled to room temperature).
• Make sure all candles are extinguished after each experiment.
• Ensure sufficient ventilation, for example, by opening windows.

Activity 1: Engaging and exploring student ideas for the candle mystery

This activity aims to set up a scenario to engage students in inquiry. When three candles of different heights are lit and covered with a gas jar, students are prompted to predict and explain which candle they think will go out first. Allow 40 minutes for the prediction discussion, experiments, and collaboration.

• Large gas jar (large enough to cover three candles)
• Three candles of different heights
• Heat-proof mat
• Hot-air gun, 240 V, 2000 W (optional: used to heat the blade to cut candles to different heights)

Worksheet 1

Preparation

Before the lesson, the setup should be prepared by the teacher or teaching assistant.

• Cut three candles to different lengths with a hot blade preheated by a hot-air gun (see figure 2).

• Align the three candles on a heat-proof mat, close enough that they can be covered with the gas jar.
• Cover the three candles with the gas jar (without lighting them, figure 3).

Practical tips :

• To ensure fair testing and expected results, ensure that the wicks are identical in length, and that the heights of the candles differ significantly.
• Perform a test run before the lesson to check that the setup works and to get a sense of how long it takes for the first candle to go out.
• Show the setup to students and encourage them to think about what would happen if we lit the candles (and replaced the gas jar). Ask them which candle they expect to go out first.
• Have them write down their own ideas first (and record them in worksheet 1) and then optionally have them discuss this in groups and then with the class. Ask them which candle they expect to go out first.
• Remove the jar, light the candles, and watch what happens. Depending on the setup (e.g., candle length, jar size), the candles should go out within a few minutes. Students often find the result (the tallest candle goes out first) mind-blowing.

• Optional: have students repeat the experiment (or watch a recording) and record the times required for each candle to go out. Combine the results and draw a graph.
• Discuss the results and encourage students to reflect on their initial predictions. Were students surprised by the results? Did the results match their predictions? Does it make them think differently about their explanation?
• A more in-depth discussion about why the tallest candle goes out first follows in Activity 2. If Activity 2 is not being used, part 1 (Why does the tallest candle go out first?) of Activity 2 can be carried out here.

Watch a demonstration of Activity 1.

You can adopt the think–pair–share approach to engage with student thinking in step 1. In this approach, students are asked to predict and explain individually which candle would go out first. They then share their predictions and explanations in groups of three or four, followed by a whole-class discussion. You can capture students’ initial ideas and reasoning and stimulate students’ thinking using the following questions:

• Why do you think the tallest or shortest candle goes out first, or why do you think the candles go out at similar times?
• After listening to your classmates’ ideas, would you change your prediction?
• How would you convince others that your prediction is correct?

Activity 2: Explaining the candle mystery

Instead of explaining to students that hot carbon dioxide rises to the top of the jar and extinguishes the tallest candle first, a discussion to help them think it through themselves will lead to better understanding. It is important to allocate time and support for students to reflect thoughtfully. They can test the explanation by monitoring changes in carbon dioxide concentration [ 2 ] and the temperature inside the gas jar. The activity takes about 40 minutes.

• Three plastic bottle caps
• Adhesive putty like Blu Tack or some adhesive tape
• Bicarbonate indicator solution (10 ml)
• Three temperature sensors (e.g., PASPORT chemistry sensor)

Evidence cards

Worksheet 2

• Timer (optional)

Part 1: Why does the tallest candle go out first?

• Ask students why they think the tallest candle goes out first. If they mention CO 2 , you can prompt them to think about how to test their hypotheses.
• Why did the candles go out before they burned down?
• How does the air in the jar change as the candle burns?
• What chemical process creates flames? What are the outputs of combustion?
• What happens to gases when they’re heated?

You can also link this to the real-life situation of escaping from fires by asking questions like:

• What are the essential actions to be followed in case of a fire inside a building?
• Why do we stay low to crawl through smoke-filled rooms or corridors?
• You can use the evidence cards (figure 4) to help guide the discussion.
• Once they have some ideas involving CO 2 build-up and temperature differences, ask how they would test their hypotheses. Encourage them to think about what variables would need to be kept the same to ensure a fair test.
• The experiments in parts 2 and 3 can be used to investigate some of these variables, or you can come up with your own.

Part 2: Monitor the carbon dioxide concentration

Safety note

A safe distance between the flame and Blu Tack/tape should be maintained to avoid melting of the Blu Tack/tape.

• Set up the experiment as for Activity 1. You can use the same candles but ensure the wicks are the same lengths.
• Fill three plastic bottle caps with bicarbonate indicator and use Blu Tack or tape to stick them at different levels inside the gas jar (figure 5).
• Repeat the procedure detailed in Activity 1, and observe colour changes to the bicarbonate indicators at the end of the experiment (figure 6).

Practical tip

To ensure fair testing, the amounts of bicarbonate indicator added to the bottle caps need to be the same.

Watch a demonstration of Activity 2a.

Part 3: Monitor the change of temperature

• Calibrate the temperature sensors if necessary.
• Set up the experiment as for Activity 1. You can use the same candles but ensure the wicks are the same lengths and the glass jar is replaced to ensure the experiment starts at room temperature.
• Connect three temperature sensors and use Blu Tack or tape to stick the sensors at different levels inside the gas jar (figure 7).
• Repeat the procedure detailed in Activity 1, and collect data for temperature changes at different levels inside the gas jar (figure 8).

The results should show that the carbon dioxide levels and temperature rise more towards the top of the jar. Discuss with students whether these results support their explanations. Are there any alternative explanations that are consistent with the results?

Activity 3: Elaborating and evaluating student learning about the candle mystery

To assess students’ deep understanding and ability to apply their explanations, you can introduce variations of the candle experiment in different contexts. Challenge your students to consider what they think might happen if we place the candles in separate jars. [ 3 ] Additionally, ask them to explore the results if we introduce an electric fan into the setup. This can be combined with another think–pair–share activity to promote discussion and evaluate their understanding of the concepts. Allow 40 minutes for the experiments and discussion.

• Portable fan

Worksheet 3

• Activity 3 explanation

Part 1: Burning candles in individual beakers

• Ask the students what they think would happen if the candles were lit in individual jars. This can be done using the think–pair–share approach.
• Secure three candles of different heights to the bench (this also works with two candles).
• Light the candles and cover each with a separate beaker (figure 9).
• Record the time required for each candle to go out.
• Repeat the experiment to get more reliable data.

To ensure fair testing, the volume inside the beaker must remain the same throughout the experiment. If a candle needs to be cut, the cut pieces should be placed inside the beaker.

Watch a demonstration of Activity 3a.

Part 2: Burning candles near a small fan

• Ask the students what they think would happen if a fan were placed in the jar. Place a portable fan near the three candles used in Activities 1 and 2, and turn the fan on.
• Repeat the procedure detailed in Activity 1, and record the time that the candle goes out.
• Repeat the experiment with the fan turned off.
• Compare the time taken for the candle to go out when the fan is on and off.

Practical tips

• To ensure fair testing, the volume inside the beaker must remain the same throughout the experiment. The electric fan should be placed inside the beaker, whether it is turned on or off.
• To repeat the experiment, you may fan the gas jar to restore it to room temperature and avoid the build-up of CO 2 , or you can use a new gas jar.

Watch a demonstration of Activity 3b.

The candles go out at similar times in the experimental setups with separate beakers or with an additional electric fan. The results contrast the experimental results in Activities 1 and 2. To ensure reliability of the results, students are encouraged to repeat their experiments, which can be performed within 5 minutes. Encourage students to provide explanations for their observations. Students are asked to construct explanations of how and why things happen in the setup using their explanations developed in Activity 2. You may give groups the model answer ( Activity 3 explanation ) at the end to compare it to their descriptions.

The activities based on simple twists to the classic candle experiment can serve to improve students’ abilities to develop, revise, and apply scientific explanations, as well as to explore scientific skills such as control of variables, hypothesis testing, and coordinating multiple pieces of evidence. As an extension activity, you could encourage students to handle quantitative data in an in-depth discussion and demonstrate their learning through report writing and group presentation. The process of predicting and explaining different unfamiliar contexts can help create valuable teachable moments that motivate students to learn.

[1] Bybee RW (2015) The BSCS 5E Instructional Model: Creating Teachable Moments . National Science Teachers Association Press. ISBN-10: 194131600X

[2] Cheng MW (2006) Learning from students’ performance in chemistry-related questions. In Yung BHW (ed.) Learning from TIMSS: Implications for Teaching and Learning Science at the Junior Secondary Level pp 51–74. Education and Manpower Bureau.

[3] Details for how to investigate candle burning: https://edu.rsc.org/resources/candle-burning-investigation-planning-an-experiment/619.article

• Watch demonstration videos of the experiments in Activities 1 ( candle mystery ), 2 ( CO 2 concentration ), and 3 ( individual beakers and electric fan ).
• Learn how to make convection currents visible using mist: Lim ZH, Shu A, Ng YH (2023) A misty way to see convection currents . Science in School 64 .
• Explore the nature of science by investigating a mystery box without peeking inside: Kranjc Horvat A et al. (2022) The mystery box challenge: explore the nature of science . Science in School 59 .
• Try some experiments with gases to illustrate stoichiometric reactions and combustion: Paternotte I, Wilock P (2022) Playing with fire: stoichiometric reactions and gas combustion . Science in School 59 .
• Learn about data visualization by sketching graphs from ‘story’ videos of everyday events: Reuterswärd E (2022) Graphing stories . Science in School 58 .
• Read about the environmental costs of fireworks: Le Guillou I (2021) The dark side of fireworks . Science in School 55 .

Steven Ka Kit Yu has been working in the education sector in teaching, research, and administrative roles. He was a secondary science teacher and a part-time lecturer in the Faculty of Education, the University of Hong Kong.

Supporting materials

Activity 3 Explanation

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REPORT ON CANDLE BURNING EXPERIMENT

This is a short report that summarizes an experiment about the heat produced from the combustion process of a candle. The main objective of this report is ∗ to give details of how the data of the experiment is collected, ∗ data transformation, ∗ model fitting, ∗ comparison of the two fits, ∗ and logical interpretations for each step.

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September 5, 2019

Make a Candle Flame Jump

A surprising science project from Science Buddies

By Science Buddies & Svenja Lohner

Illuminating science: learn what keeps a candle burning--and how you can light a candle almost out of thin air. 

George Retseck

Key Concepts Chemistry Chemical reactions States of matter Combustion

Introduction There are many occasions to light candles. Have you ever looked closely at the flame? Which part of the candle is actually burning? Can you tell? Is it the wick, the solid wax, the liquid wax or something else? In this activity you will light some candles to find out—no special occasion required!

Background Whether they are on a birthday cake or dinner table or menorah, most candles we use today are wax-dipped candles. This style of candle dates back to the ancient Romans. Through the center of the wax runs a wick, which is usually made from cotton or other material that can absorb liquids well. So how do these two materials come together to help a candle burn steadily?

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A lit candle might seem simple, but it is actually an example of a multi-step process resulting in combustion—and the glowing flame you see. Combustion is the result of a chemical reaction in which oxygen gas reacts with the substance that is being burned. The combustible material in a candle—or its fuel—is the wax. But before the wax can become fuel it first needs to get hot enough. To start that heating process, you first need to light the wick with another source of fire, such as a match. As the wick burns down the heat of the flame melts the wax around the wick. Because the wick is absorbent it sucks the liquid wax into the wick and upward into the flame. Once the liquid wax gets hot enough, it then turns from a liquid into a gas. The hot gas then reacts with the oxygen from the air and is burned, creating the candle flame that we see. This means that the candle flame is actually created by the burning wax gas—or vapor—and not by the wick itself or the solid or even liquid wax.

After lighting a candle, it might flicker or sputter at first, but then it usually burns fairly steadily. As the heat of the wax vapor flame melts more of the solid wax it creates more fuel for the flame to burn. The candle will only go out once it runs out of wax or oxygen—or gets blown out. After a candle goes out you can actually see the wax vapor escaping as a stream of white smoke. If you hold a match into that smoke, the candle will catch fire again—without even touching the wick! Don't believe it? Then try this activity to see for yourself!

Adult helper

Several small, narrow, birthday candles

Matches or a lighter

Wet sand (or another non-flammable substance to hold your candles up—you could also use cake or a cupcake!)

Dish or bowl for your wet sand or other candle-holding substance

Fireproof work area

Bowl filled with water or a fire extinguisher

Preparation

Take your materials to a fireproof work area.

Make sure you have an adult helper assist you while doing this activity.

Keep the bowl of water or the fire extinguisher close throughout the activity in case you need it.

Prepare your wet sand or other non-flammable base material in the dish or bowl.

Stand one candle up in your wet sand or other material, packing it around the candle base to make sure it is secure.  

With the help of an adult, light a match. Hold the flame close to the candle's wick, but don't touch the wick with the flame. What do you observe? Does the candle light?

Next touch the candle's wick with the flame of the match. Hold it there for about a second. What happens when you touch the wick with the flame? If the wick did not ignite, light it now.

Watch the candle burn for a couple of seconds. Can you describe the flame? How does it look?

Blow out the candle and watch what happens. Do you see white smoke escaping from the wick?

Light the candle again then light another match. While the match is still burning blow out the candle. Immediately afterward hold the flame of the match into the white smoke of the blown-out candle, close to the wick but without touching it. What happens? Does the candle light again? Why or why not?

Blow out the burning candle. Now stand two candles next to each other in your wet sand (or other material) so that they are secure and will not fall over. They should almost touch each other. Light both candles with a match.

While both candles are burning point the end of a straw to one of the flames. Blow through the straw to extinguish just one of the flames. The other candle should keep burning. What happens after you extinguish one of the candles? Can you explain your observation?

Repeat this step several times. Do you always get the same results? Can you tell from your observations which part of the candle is burning? Why?

Extra: Place three or more candles next to each other. With a straw, blow out one of the candles, but keep the others burning. What happens to the blown-out candle? Then blow out two of the candles but keep one burning. Can you see the flame jumping from one candle to another?

Extra: Try the activity with candles made of paraffin or beeswax. Do you get the same results for these materials as well?

Extra: Look at a candle's flame in more detail. Can you see that the flame has different colors? Do your own research to find out why there are different colors. Can you find out which part of the flame is the hottest or coolest?

Observations and Results Could you make a candle's flame jump from one candle to another? The first time you lit your candle you most likely had to touch the wick with the flame of your match. This makes the wick catch fire, which starts the combustion reaction. The wax around the wick starts melting, and it is from this liquid wax that vapor is created inside the flame. The wax vapor starts to burn and creates the stable candle flame that you see. When you blew out the candle you should have seen white smoke rising up into the air from the wick. This is the wax vapor, which becomes visible as it condenses into small liquid droplets in the cooler air.

If you touched the wax vapor (white smoke) with another flame, the candle should have immediately lit up again. This time you didn't even have to touch the wick or another part of the candle. Lighting the vapor is enough to get the candle burning again. When you placed two or more candles next to each other and blew one out the burning candle's flame should have reignited the wax vapor of the extinguished one. You might have realized that it is actually quite hard to keep a candle extinguished when it is so close to a burning one. It lights up again due to the fact that the wax vapor of the blown-out candle is touching the remaining candle flame. What you end up seeing is the candle flame jumping from one candle to another!

Cleanup Make sure to extinguish all your candles at the end of your experiment. Once the matches are cooled down, you can throw them in your regular trash. Clean up your work area and wash your hands with soap and water.

More to Explore Candle Science , from the National Candle Association Flame Out , from the American Chemical Society Fire-Fighting Foam , from Scientific American A Candle Seesaw Balancing Act , from Scientific American STEM Activities for Kids , from Science Buddies

This activity brought to you in partnership with Science Buddies

Burning Questions About a Candle

Introduction.

Yogi Berra once said, "You can observe a lot by just watching." What he meant by this is that observation requires more than simply using your eyes . It also requires critical thinking during the observation process. You should be asking yourself questions about what you are seeing and why the behavior you are observing is taking place. That is, you should be formulating hypotheses and testing those hypotheses on a limited basis. This type of observation is extremely important in science since it provide the main method of acquiring data, detecting errors and unexpected occurrences, and achieving ultimate success in whatever component of science you are engaged in.

The key aspect of critical observation involves self-questioning. That is, you must learn to formulate questions based on what you are seeing that you can either answer immediately or attempt to answer at a later time. This type of question/answer dialogue, carried out internally, provides the mental aspect to the observation process which is so crucial in extending the data acquisition to understanding and application. (For example, see this note on the discovery of penicillin.)

Are you ready to test your powers of observation by answering...

Activity: Observations of a Burning Candle

Materials needed.

Attached here is a printable form that has most of the questions and directions below, but with space for you to write in your answers and observations while you work. Have fun!

Observations to make before you light the candle

Answer the following questions concisely . That is, use short sentences or sentence fragments, and only say what really needs to be recorded. You may want to work in pairs or small groups, each writing down observations, then periodically comparing notes and asking each other questions. If you do it this way, just remember: don't make critical comments! Be critical in your thinking, in the sense of always asking yourself "What does that mean anyway?" and not in the sense of "That's clearly wrong" or "What a dumb observation." Be positive in your approach, focus on the candle, and keep asking yourself questions in your own mind, especially questions that lead to further observations and more questions.

Do some physical "tests" on the candle using what you have on you or laying around the room. What do these tests tell you about its properties?

Do any of these tests give you an indication of the nature of the candle components at the molecular level? What do you know about the chemical nature and/or composition of these components?

Hypothesize what will happen when you light the candle and start it burning

Now, light the candle and watch what happens.

• It is important that you record your observations as quickly as you can and then come back to some of them later for further thought and extended observation.
• Try to make at least 10 distinct and separate observations initially. (Be aware that individual observations numbering over 100 have been recorded by others.)

It may take you a while to begin to think about what is happening. Be patient and work at the process. Once you begin to see how to ask questions related to what you are seeing, a snowball effect will occur that should open up whole new areas of observation for your critical consideration. Be sure to write down all of your thoughts and observations as they occur. Don't try to be critical of the material you write down, but simply put it down as quickly as possible. You will have plenty of opportunity later for evaluation and grouping of your data.

Take one observation that you recorded above and:

• Break it down into macroscopic versus molecular levels.
• See if you can coordinate what is happening between what you've physically observed (that is, the macroscopic level) and the molecular level.
• Most important, speculate on what is actually happening at each of these levels.
• What changes in that property occurred during the burning process? Go into as much detail as you can.

Now, pick another observation or two and carry out the same level of in-depth analysis. Try to relate the observations you made above to those that you make in this section.

You should find that as you practice this process of observation and recording your thoughts, you become better at asking questions about what is happening, and then writing down answers. This iteration is part of "doing science."

Repeat this process several times: this repetition is also part of doing science.

Now try to "watch" yourself observing and asking yourself questions:.

• How can you do this better, with conscious awareness?
• Can you see possible ways of getting the answers while you are asking the questions?

Do White Candles Burn Faster Than Colored Candles

Introduction.

This science fair project topic that tests white candles vs colored candles with respect to how long they take to burn requires commonly available supplies and can be performed easily. You can apply the knowledge gained from your day-to-day activities involving burning candles. Background information on the project would come in handy during the execution. Plotting a graph of the different rates at which the candles burn helps in the discussion.

Do Colored Candles Burn Faster Than White Candles Project

Problem statement.

The experiment proves which candle burns faster, white or any of the colored ones.

The experiment would establish the fact that white colored candles burn quicker than white candles due to the chemicals present in them.

Candles of different colors and white are burned up to a specific mark on their bodies and the time taken is checked to analyze which one burns the fastest.

• White and colored candles of the same brand, same size and shape
• Permanent marker
• Trim the wicks of the candles such that all are of the same length and place them about 10 inches apart on a table so that the burning of any candle doesn’t affect the adjacent one.
• Mark a line on the candle that is one inch from the top with the permanent marker.
• Light them simultaneously and observe the time it takes to burn up to the mark.
• Record the observation data in a table format as given below.

• Plot a graph (a bar graph would be good) with the color as the X-axis (independent variable) and the time taken to burn up to the mark as the Y-axis (dependent variable). You can prepare a proper lab report and charts too.

All the colored candles take times that are lesser than the white candle. Note that the size and brand of the candles are constant and hence they are the controlled variables

Result/Conclusion

The white candle burns slower than the colored candles.

Explanation

The colored candles are seen to burn less than the white ones as the colored ones have dyes that are nothing but chemicals which make the candles hotter and burn them quicker.

Background Research

The candles are nothing but a mass of wax with a wick in the middle. Chemical compounds are mixed together to make wax the major ones being beeswax and paraffin wax. The wick is a piece of braided cotton the thickness of which, apart from the wax, also decides the time taken for a candle to burn.

There can be different kinds of candles such as tea light, taper and jar candles. Floating candles can be put in water while outdoor candles are the bigger varieties. There are the scented types and the birthday candles are skinny. With the advent of electricity, candles are now mostly used for emergency purposes.

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Experiment #1

A candle flame is actually a chemical reaction in action! Candle wax is one of the chemicals in the reaction. Can you guess what the wax reacts with? Find out in this experiment!

1. Ask the adult you are working with to light the candle.

2. Watch the candle flame start out small and get bigger. Notice how some of the wax near the wick melts.

3. As the flame burns, the wax from the candle is reacting with something else to make the flame. 

What do you think it might be?

4. Ask the adult you are working with to carefully place a glass jar over the candle and to leave it there.

 What to expect 

The flame will go out.

What’s happening in there?

Why does the flame go out when the jar is covering it?

The substance that reacts with the candle wax is oxygen. It comes from the air. Putting the jar over the candle keeps oxygen from outside the jar from getting in.  The reaction can only use the oxygen that is already in the jar. So, when that oxygen is used up, the reaction can’t keep going. Running out of oxygen makes the flame go out.

Experiment #2

Another chemical reaction you probably know is the reaction between vinegar and baking soda. This reaction produces a gas called carbon dioxide. This gas can be used to put out a flame. Let’s try it!

1. Ask the adult you are working with to light the tealight candle.

2. Place about two teaspoons of baking soda in the jar.

3. Next pour about two tablespoons of vinegar in a cup.

4. When you are ready, carefully pour all the vinegar from the cup into the jar with the baking soda.

5. Hold your hand gently over the top to keep most of the carbon dioxide in the jar.

6. Ask the adult you are working with to carefully pour the carbon dioxide gas onto the flame. Be sure no liquid comes out – just the gas.

 What to expect?

The flame should go out.

Why does the flame go out when carbon dioxide is poured on it?

Carbon dioxide molecules are heavier than air. Because of this, they push the oxygen and other molecules in the air out of the way as they sink down over the flame and candle. When oxygen is pushed away from the wick, it can’t react with the wax anymore. This makes the flame go out.

Next time you blow out a candle, think about what your breath is actually doing. Why do you think blowing on a candle flame makes it go out?

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Middle School Science Blog

Free lesson plans and resources for grades 5-8 by liz belasic (liz larosa), candle observation lab.

Materials – per 2 students

• Student Handout ( Candle Observations )
• votive candle
• small beaker
• large beaker
• I light the candles for the students in this age group (6th)

• Discuss how candles work and the fire triangle ( link )
• Discuss combustion and the chemical reactions that takes place when a candle burns
• Explain the lab procedures and remind students of safety protocols
• all students will place the larger beaker over the candle at the same time and watch as the candle goes out
• Share observations and discuss

I like to use this lab as part of my physical and chemical changes unit, it is such a classic and the kids make some great observations and ask lots of good questions.

• BrainPOP – fire video and resources
• Naked Scientist – water vapor and candles
• Candle Science – how do candles burn?

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Candle chemistry

Experiment with the chemistry of candles and make a flame jump through the air.

Make  a blown out candle relight as if by magic.

ExpeRiment  to find out how long a candle will burn in different amounts of air.

Learn  about the chemistry of how a candle burns.

About this activity

Lisa and Josh make a candle relight as if by magic. They investigate how long it takes for a covered candle to go out, and find out why a candle can keep burning for a longer time in a larger jar than in a small one.

In this fun, free science experiment to do at home with young children, Lisa shows Josh how to relight a candle without touching the wick. When a candle is blown out, the wick stays hot, and wax continues to be drawn up through it before evaporating. This wax gas above the candle can be relit, meaning that a flame will appear to jump from Lisa’s lighter to the candle wick.

Josh times how long it takes for candles to go out when covered by different sized jars. A candle flame is the result of a chemical reaction between wax gas and oxygen in the air. When you trap the candle in a jar, it only has a limited amount of oxygen. Josh finds out that in larger jars, there’s more oxygen so the candle can keep burning for longer, but that the flame will eventually go out.