Teacher"s Overview


In this investigation, college student are tested to make mindful observations around a burn candle to uncover the chemical and also physical changes that make it work.

You are watching: Is a candle burning a chemical change


Students will certainly desribe their observations about a burn candle to uncover the chemical and physical transforms that do it work.


Be sure to wear safety goggles if making near observations, tie your hair ago if you have long hair, and always be conscious of where the flame is through respect to your clothing—do not lean over the flame.Burning candles are open flames the can reason burns. Liquid wax is hot and can cause burns come the skin.

Materials because that Each Group

Tea light candleMatchesSmall maker or evaporating dish (such together 50 mL or 100 mL)BalanceRuler or meter stickString (for measuring circumference)Stopwatch

Time Required

One class period, approximately 45–50 minutes.

Lab Tips

Tea candles have the right to be to buy in huge quantities, as have the right to tapered candles from hardware stores. Candles of different colors, sizes, and also shapes deserve to enrich the observations made by the class.

We space all familiar with burning candles, yet how much have we really seen while looking in ~ one? In this exercise you will certainly be tested to observe a burn candle with the lens of chemistry. You might be surprised by how much is yes, really happening in what seems choose a acquainted process!

First we will shot to watch details past our usual method of looking in ~ a candle, and then we will look for evidence of the physics or chemistry nature of any changes that space taking place. Take treatment in recording your observations—try to imagine that you have actually never seen a burn candle before!

Obtain a tea irradiate candle, matches, and any measuring equipment easily accessible to you. Before lighting the candle, make 3 qualitative observations and also three quantitative monitorings of the candle.Qualitative observations describe qualities or characteristics, quantitative observations involve quantities, or measurements. You might choose among many properties to observe: color, texture, mass, physics dimensions, density, aroma… or any kind of others you can think of. Usage as countless of her physical senses as possible, and also be sure to encompass units for any of her quantitative observations.

Use a match to very closely light the candle.Repeat the procedure of do qualitative and also quantitative monitorings of the burning candle, this time making 6 of each kind of observation. (Some of your observations might relate to properties you have already recorded, that may be an altering now that the candle is burning.) when again usage all her senses to make qualitative observations. Ask yourself what you can measure for the quantitative observations.

For her observations and measurements, consider not only the physical candle, but likewise consider its influence on the waiting in the an are surrounding it.

Now lay out a thorough drawing that the burning candle, an enlargement that the part about a centimeter from the peak of the candle to the topmost guideline of the flame:

Label the adhering to regions the the candle in your drawing:

solid waxliquid waxregion of wick without flameregion that wick v flameregion of the wick the glows

Now identify as plenty of different aspects of the flame itself and label castle in the drawing. As soon as you have actually completed recording your observations and also drawings, prepare come blow the end the candle, and also be all set to make further observations as you carry out this!Blow out the candle and record two qualitative and also two quantitative monitorings of the candle instantly after the is extinguished:

Qualitative observationsQuantitative observations

Interpreting Evidence

component One

Now the we have actually paid close attention to the properties of a burning candle, us can start to analyze what we’ve checked out in terms of phase changes and also chemical reactions.In a phase readjust (from solid to fluid or from fluid to gas) the corpuscle of a substance (in this situation the molecules of wax) will adjust the plan they have actually with every other. Together a solid they will be very closely packed together and unable to relocate freely. In the fluid they will have the ability to flow about each other yet will still it is in close together, and also as a gas they will certainly fly freely apart yet they will still be wax molecules and also will have the very same structure they had as molecule in the solid and also the fluid phases:


wax from plants and animals have various structures. Here is a molecule comparable to wax— a material that is typically a major component the the candle wax.

In the boxes below, usage small, solitary shapes to represent entire wax molecules, and also sketch their setup in the three physical phases:


based on your monitorings of the burning candle, go you uncover evidence because that the adjust from the solid wax phase to the liquid wax phase?


explain this proof as especially as possible.


describe this evidence as specifically as possible.

Did you find evidence because that the change from the fluid wax phase to the gaseous wax phase?

A physics candle is composed of wax neighboring a wick. Look increase the meaning of the verb “to wick,” and also write it down.Describe the wicking process in the burn candle, and also be sure your description includes the physical state of the wax and the wick.As a candle burns, the wax slowly disappears native sight. Is over there a physical readjust in the wax that would certainly account because that this disappearanceIf the wax was merely undergoing physical change, would you mean the candle to produce heat and also light as it does as soon as a candle burns?The process of burning (as protest to evaporating) is a chemistry reaction, a chemistry change. The wax molecules are undergoing a chemistry change; lock are changing into different molecules by reacting v a problem in the air. What is this problem in the air the a candle requirements to burn?

Interestingly, a candle releases energy through the exact same kind of reaction the your body supplies to achieve energy. Hold your breath because that a moment. What is her body craving? This is the same substance the candle needs to burn in a chemical change that we contact combustion.

We deserve to represent the burning of a candle choose this:


finish the adhering to sentence that restates this equation:

Two molecule of wax react v ____________ molecules of oxygen come produce__________ molecules of _____________________________ and also ___________ molecule of __________________.

We are not conscious of oxygen in the air due to the fact that it is an odorless and also colorless gas, and also at the temperature that a burn candle, both the CO2 and the H2O are additionally gases that room invisible to us. We can see proof of chemistry change, however, if us restrict the amount of oxygen the is enabled to react with the wax.

If less oxygen is available, one feasible outcome in the combustion of wax is

Relight the candle and also lower the bottom the a small beaker or a clear clock glass into the fire so that the fire touches the surface ar of the glass. Hold it there because that a moment (where the restricts some of the air flow to the flame) and then eliminate it.

What carry out you watch on the bottom that the beaker? What might this problem be and also where did the come from?How does this carry out evidence the a chemical reaction is acquisition place?Wipe the bottom of the manufacturer clean and place an ice cube inside it. Hold the beaker number of centimeters above (not in) the fire and enable the candle come burn. Can you watch a substance creating on the bottom of the beaker? What might this problem be and also where did the come from? can it have actually come native the melting ice inside the beaker?Consider the fire itself. Is the flame a substance created by the candle? What monitorings lead you to think the the flame is matter? In what means does the fire seem favor energy?Is the adhering to statement true or false: “As a candle burns, wax turns right into fire.” If this isn’t an accurate statement, deserve to you restate that correctly?

Finally, permit us consider the physical step of the wax together it reacts through the oxygen to produce carbon dioxide and water. Prepare to watch carefully! Blow out the candle and an extremely quickly lug a complement close come the wick. Try to notification exactly whereby the lit wooden splint is v respect to the wick as soon as the candle reignites.

Do this number of times to view if you observe something interesting. Note any type of evidence you have observed the helps to recognize the physical step of the wax once it reacts through oxygen.

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What step is the wax in once it mixes v oxygen in the air and undergoes a chemical change?Based on your observations, in which step (solid, liquid, or gas) is the wax most likely to experience a chemical change?Explain why this is the case based upon your sketches the wax in solid, liquid, and also gas phases.How can this (your price to question above) describe a authorize that states NO SMOKING close to the pumps at a gas station?Look earlier at her diagrams that the candle flame. Have the right to you recognize the an ar where the wick chin is undergoing combustion? whereby is this region?What is fire? Is it matter or is that energy? explain your answer.In a short paragraph, summary the alters that a candle undergoes as soon as it burns. Combine the complying with words right into the i in a meaningful way: wax, wick, phase change, chemistry reaction, vaporize, melt, transforms, solid, liquid, gas, energy, light, and heat.