Teacher"s Overview


In this investigation, students are tested to make careful observations around a burn candle to discover the chemical and physical changes that make it work.

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Students will desribe your observations around a burning candle to discover the chemical and also physical alters that make it work.


Be certain to wear safety goggles while making nearby observations, tie her hair ago if you have long hair, and always be aware of wherein the flame is v respect to her clothing—do no lean end the flame.Burning candles are open flames that can cause burns. Fluid wax is hot and can reason burns to the skin.

Materials because that Each Group

Tea irradiate candleMatchesSmall manufacturer or evaporating food (such as 50 mL or 100 mL)BalanceRuler or meter stickString (for measuring circumference)Stopwatch

Time Required

One class period, about 45–50 minutes.

Lab Tips

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

We are all familiar with burn candles, but how much have actually we really checked out while looking at one? In this practice you will be tested to observe a burning candle v the lens of chemistry. You may be surprised by just how much is yes, really happening in what seems choose a acquainted process!

First we will shot to observe details past our usual method of looking in ~ a candle, and then we will certainly look for evidence of the physics or chemical nature of any type of changes that room taking place. Take care in recording her observations—try to imagine that you have actually never viewed a burning candle before!

Obtain a tea irradiate candle, matches, and any measure up equipment accessible to you. Before lighting the candle, make three qualitative observations and also three quantitative observations of the candle.Qualitative observations describe attributes or characteristics, quantitative observations involve quantities, or measurements. You may choose among many nature to observe: color, texture, mass, physical dimensions, density, aroma… or any kind of others you deserve to think of. Usage as plenty of of her physical senses together possible, and also be sure to encompass units for any of your quantitative observations.

Use a match to very closely light the candle.Repeat the process of make qualitative and quantitative observations of the burn candle, this time making six of each type of observation. (Some of her observations might relate to properties you have already recorded, that may be transforming now that the candle is burning.) when again use all her senses to do qualitative observations. Ask you yourself what you can measure because that the quantitative observations.

For her observations and measurements, think about not just the physical candle, but additionally consider its influence on the waiting in the space surrounding it.

Now sketch a in-depth drawing of the burn candle, an enlargement the the section about a centimeter from the top of the candle come the topmost tip of the flame:

Label the following regions of the candle in her drawing:

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

Now differentiate as countless different aspects of the flame itself and label them in the drawing. When you have actually completed recording her observations and drawings, prepare come blow out the candle, and also be all set to make additional observations as you execute this!Blow out the candle and record 2 qualitative and also two quantitative observations of the candle automatically after it is extinguished:

Qualitative observationsQuantitative observations

Interpreting Evidence

component One

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


waxes from plants and animals have different structures. Right here is a molecule similar to wax— a product that is generally a major component that the candle wax.

In the box below, use small, solitary shapes to represent entire wax molecules, and also sketch their arrangement in the three physical phases:


based on your monitorings of the burning candle, walk you uncover evidence for the change from the solid wax step to the liquid wax phase?


describe this proof as particularly as possible.


define this evidence as especially as possible.

Did you discover evidence because that the adjust from the fluid wax phase to the gas wax phase?

A physical candle is created of wax surrounding a wick. Look up the definition of the verb “to wick,” and write it down.Describe the wicking process in the burning candle, and also be certain your description consists of the physical state the the wax and the wick.As a candle burns, the wax progressively disappears native sight. Is there a physical change in the wax that would certainly account because that this disappearanceIf the wax was just undergoing physics change, would you suppose the candle to create heat and also light together it does once a candle burns?The procedure of burn (as opposed to evaporating) is a chemistry reaction, a chemistry change. The wax molecules room undergoing a chemical change; they are an altering into various molecules by reacting with a substance in the air. What is this substance in the air that a candle requirements to burn?

Interestingly, a candle releases energy through the exact same kind of reaction the your body provides to achieve energy. Host your breath for a moment. What is your body craving? This is the same substance the candle demands to burn in a chemical change that we call combustion.

We deserve to represent the combustion of a candle prefer this:


complete the following sentence that restates this equation:

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

We room not conscious of oxygen in the air since it is one odorless and colorless gas, and also at the temperature of a burning candle, both the CO2 and also the H2O are also gases that space invisible come us. We have the right to see proof of chemistry change, however, if we restrict the quantity of oxygen the is allowed to react through the wax.

If much less oxygen is available, one possible outcome in the burning of wax is

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

What execute you observe on the bottom of the beaker? What can this problem be and also where did the come from?How walk this administer evidence the a chemical reaction is taking place?Wipe the bottom the the manufacturer clean and also place an ice cream cube within it. Organize the beaker numerous centimeters above (not in) the flame and permit the candle come burn. Deserve to you check out a substance forming on the bottom that the beaker? What might this substance be and also where did that come from? can it have come from the melting ice cream inside the beaker?Consider the flame itself. Is the flame a substance created by the candle? What monitorings lead you come think that the fire is matter? In what ways does the flame seem like energy?Is the complying with statement true or false: “As a candle burns, wax turns right into fire.” If this isn’t an exact statement, can you restate the correctly?

Finally, permit us take into consideration the physical step of the wax as it reacts v the oxygen to create carbon dioxide and also water. Prepare to observe carefully! Blow the end the candle and really quickly lug a enhance close to the wick. Try to notification exactly wherein the lit wooden splint is with respect come the wick as soon as the candle reignites.

Do this several times to see if you observe something interesting. Note any evidence you have observed that helps to recognize the physical step of the wax when it reacts v oxygen.

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What step is the wax in once it mixes v oxygen in the air and also undergoes a chemistry change?Based on her observations, in which phase (solid, liquid, or gas) is the wax most most likely to undergo a chemistry change?Explain why this is the case based on your sketches the wax in solid, liquid, and also gas phases.How could this (your answer to question above) describe a sign that says NO SMOKING near the pumps in ~ a gas station?Look back at your diagrams of the candle flame. Have the right to you recognize the an ar where the wick itself is experience combustion? where is this region?What is fire? Is it issue or is the energy? define your answer.In a brief paragraph, summary the transforms that a candle undergoes when it burns. Incorporate the following words into the i in a coherent way: wax, wick, step change, chemical reaction, vaporize, melt, transforms, solid, liquid, gas, energy, light, and also heat.