Teacher"s Overview


In this investigation, students are tested to make mindful observations about a burn candle to uncover the chemical and also physical transforms that make it work.

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Students will certainly desribe your observations about a burning candle to find the chemical and physical transforms that do it work.


Be certain to wear security goggles if making close observations, tie her hair ago if you have long hair, and constantly be aware of whereby the fire is v respect to her clothing—do no lean over the flame.Burning candle are open flames that can reason burns. Liquid wax is hot and also can reason burns come the skin.

Materials because that Each Group

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

Time Required

One class period, roughly 45–50 minutes.

Lab Tips

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

We are all acquainted with burning candles, yet how much have we really seen while looking in ~ one? In this practice you will be challenged to watch a burn candle with the lens the chemistry. You might be surprised by just how much is yes, really happening in what seems prefer a familiar process!

First us will shot to watch details beyond our usual means of looking at a candle, and then we will look for proof of the physics or chemistry nature of any changes that are taking place. Take care in recording your observations—try to imagine the you have actually never seen a burn candle before!

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

Use a complement to very closely light the candle.Repeat the process of make qualitative and also quantitative observations of the burning candle, this time making six of each type of observation. (Some of her observations might relate to properties you have currently recorded, that might be an altering now that the candle is burning.) once again usage all your senses to make qualitative observations. Ask you yourself what you have the right to measure because that the quantitative observations.

For her observations and also measurements, take into consideration not only the physics candle, but additionally consider its affect on the air in the room surrounding it.

Now map out a comprehensive drawing that the burning candle, an enlargement of the section about a centimeter native the peak of the candle to the topmost pointer of the flame:

Label the complying with regions the the candle in her drawing:

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

Now identify as countless different facets of the fire itself and label them in the drawing. Once you have actually completed recording her observations and also drawings, prepare come blow the end the candle, and also be ready to make additional observations together you do this!Blow out the candle and record two qualitative and also two quantitative observations of the candle automatically after it is extinguished:

Qualitative observationsQuantitative observations

Interpreting Evidence

part One

Now that we have paid close fist to the properties of a burn candle, we can begin to interpret what we’ve viewed in terms of phase changes and chemical reactions.In a phase adjust (from heavy to fluid or from fluid to gas) the particles of a substance (in this situation the molecule of wax) will change the plan they have with every other. Together a solid they will certainly be 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 fly freely apart however they will still be wax molecules and will have actually the exact same structure they had actually as molecules in the solid and the fluid phases:


waxes from plants and animals have various structures. Right here is a molecule comparable to wax— a material that is generally a major component that the candle wax.

In the boxes below, use small, single shapes come represent entire wax molecules, and sketch their plan in the three physical phases:


based on your monitorings of the burning candle, walk you find evidence because that the adjust from the heavy wax phase to the fluid wax phase?


explain this proof as especially as possible.


describe this proof as particularly as possible.

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

A physical candle is written of wax bordering a wick. Look up the an interpretation of the verb “to wick,” and also write it down.Describe the wicking process in the burn candle, and be sure your description consists of the physics state of the wax and also the wick.As a candle burns, the wax slowly disappears indigenous sight. Is there a physical change in the wax that would certainly account for this disappearanceIf the wax was just undergoing physical change, would you intend the candle to create heat and light as it does once a candle burns?The process of burning (as protest to evaporating) is a chemical reaction, a chemistry change. The wax molecules room undergoing a chemistry change; lock are transforming into various molecules by reacting v a problem in the air. What is this problem in the air that a candle needs to burn?

Interestingly, a candle releases energy through the same kind the reaction that your body uses to obtain energy. Hold your breath for a moment. What is your body craving? This is the exact same substance the candle requirements to burn in a chemical adjust that we speak to combustion.

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


complete the complying with sentence the restates this equation:

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

We space not conscious of oxygen in the air due to the fact that it is one odorless and colorless gas, and also at the temperature of a burning candle, both the CO2 and the H2O are likewise gases that space invisible to us. We can see proof of chemical change, however, if us restrict the quantity of oxygen that is allowed to react through the wax.

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

Relight the candle and also lower the bottom that a tiny beaker or a clear clock glass right into the flame so that the flame touches the surface ar of the glass. Organize it there because that a moment (where it restricts few of the air circulation to the flame) and also then remove it.

What perform you observe on the bottom that the beaker? What can this substance be and also where did it come from?How does this carry out evidence the a chemistry reaction is taking place?Wipe the bottom that the maker clean and also place an ice cream cube inside it. Host the beaker number of centimeters over (not in) the fire and enable the candle to burn. Deserve to you see a substance creating on the bottom of the beaker? What might this substance be and where did the come from? can it have actually come native the melting ice cream inside the beaker?Consider the flame itself. Is the fire a substance developed by the candle? What observations lead you to think the the fire is matter? In what means does the flame seem favor 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 it correctly?

Finally, let us think about the physical phase of the wax as it reacts v the oxygen to create carbon dioxide and water. Prepare to watch carefully! Blow the end the candle and an extremely quickly carry a enhance close to the wick. Try to notice exactly where the lit wooden splint is with respect to the wick when the candle reignites.

Do this numerous times to see if you observe something interesting. Note any type of evidence you have observed the helps to identify the physical phase of the wax as soon as it reacts v oxygen.

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What phase is the wax in when it mixes with oxygen in the air and also undergoes a chemical change?Based on her observations, in which phase (solid, liquid, or gas) is the wax most likely to experience a chemistry change?Explain why this is the case based upon your sketches of wax in solid, liquid, and gas phases.How can this (your prize to concern above) explain a sign that states NO SMOKING near the pumps at a gas station?Look back at your diagrams the the candle flame. Have the right to you identify the an ar where the wick chin is undergoing combustion? wherein is this region?What is fire? Is it issue or is it energy? explain your answer.In a brief paragraph, summarize the changes that a candle undergoes when it burns. Combine 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.