Teacher"s Overview


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

You are watching: Burning candle physical or chemical change


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


Be sure to wear safety goggles while making nearby observations, tie her hair earlier if you have long hair, and always be aware of whereby the flame is with respect to your clothing—do no lean end the flame.Burning candle are open flames the can reason burns. Liquid wax is hot and can reason burns to the skin.

Materials because that Each Group

Tea light candleMatchesSmall beaker or evaporating dish (such as 50 mL or 100 mL)BalanceRuler or meter stickString (for measure up circumference)Stopwatch

Time Required

One course period, roughly 45–50 minutes.

Lab Tips

Tea candles have the right to be purchased in large quantities, as have the right to tapered candle from hardware stores. Candle of various colors, sizes, and shapes deserve to enrich the observations made through the class.

We space all familiar with burning candles, but how much have actually we really watched while looking at one? In this exercise you will certainly be challenged to observe a burn candle v the lens the chemistry. You may be surprised by exactly how much is really happening in what seems like a familiar process!

First we will shot to observe details past our usual method of looking in ~ a candle, and also then we will certainly look for proof of the physical or chemical nature of any changes that room taking place. Take care in recording her observations—try come imagine the you have never checked out a burn candle before!

Obtain a tea irradiate candle, matches, and any measure equipment easily accessible to you. Before lighting the candle, make 3 qualitative observations and three quantitative observations of the candle.Qualitative observations describe attributes or characteristics, quantitative monitorings involve quantities, or measurements. You might choose amongst many nature to observe: color, texture, mass, physics dimensions, density, aroma… or any type of others you deserve to think of. Use as many of your physical senses as possible, and also be certain to encompass units for any of your quantitative observations.

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

For her observations and measurements, think about not only the physical candle, but additionally consider its affect on the waiting in the room surrounding it.

Now sketch a detailed drawing the the burn candle, an enlargement the the part about a centimeter indigenous the optimal of the candle come the topmost reminder of the flame:

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

solid waxliquid waxregion of wick there is no flameregion that wick with flameregion of the wick the glows

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

Qualitative observationsQuantitative observations

Interpreting Evidence

component One

Now that we have paid close attention to the nature of a burning candle, we can start to translate what we’ve watched in regards to phase changes and also chemical reactions.In a phase change (from heavy to liquid or from fluid to gas) the particles of a problem (in this instance the molecules of wax) will change the setup they have with each other. Together a heavy they will be very closely packed together and also unable to move freely. In the liquid they will have the ability to flow about each other but will still it is in close together, and as a gas they will fly easily apart but they will certainly still be wax molecules and will have the very same structure they had actually as molecule in the solid and the fluid phases:


wax from plants and also animals have different structures. Right here is a molecule comparable to wax— a product that is generally a significant component of the candle wax.

In the box below, use small, solitary shapes to represent whole wax molecules, and sketch their setup in the 3 physical phases:


based upon your observations of the burn candle, did you uncover evidence for the readjust from the solid wax step to the liquid wax phase?


describe this evidence as particularly as possible.


explain this proof as especially as possible.

Did you discover evidence for the readjust from the fluid wax phase to the gas wax phase?

A physical candle is composed of wax bordering a wick. Look increase the meaning of the verb “to wick,” and write the down.Describe the wicking process in the burn candle, and be certain your description consists of the physical state of the wax and the wick.As a candle burns, the wax gradually disappears from sight. Is over there a physical change in the wax that would certainly account because that this disappearanceIf the wax was simply undergoing physical change, would certainly you mean the candle to develop heat and also light together it does once a candle burns?The process of burn (as opposed to evaporating) is a chemistry reaction, a chemical change. The wax molecules room undergoing a chemistry change; they are an altering into different molecules by reacting through a substance in the air. What is this problem in the air the a candle demands to burn?

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

We can represent the combustion of a candle choose this:


finish the following sentence that restates this equation:

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

We space not conscious of oxygen in the air since it is an odorless and also colorless gas, and at the temperature the a burn candle, both the CO2 and also the H2O are also gases that space invisible come us. We deserve to see proof of chemical change, however, if we restrict the lot of oxygen the is allowed to react v the wax.

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

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

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

Finally, let us take into consideration the physical phase of the wax as it reacts with the oxygen to develop carbon dioxide and water. Prepare to watch carefully! Blow out the candle and an extremely quickly carry a complement close to the wick. Shot to an alert exactly wherein the lit wooden splint is v respect to the wick as soon as the candle reignites.

Do this numerous times to see if you observe something interesting. Note any evidence you have actually observed the helps to determine the physical step of the wax as soon as it reacts with oxygen.

See more: How To Say Can You Speak Spanish In Spanish ? Do You Speak Spanish

What step is the wax in when it mixes through oxygen in the air and undergoes a chemistry change?Based on your 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 upon your sketches that wax in solid, liquid, and also gas phases.How can this (your answer to concern above) describe a authorize that states NO SMOKING close to the pumps in ~ a gas station?Look earlier at your diagrams of the candle flame. Have the right to you determine the an ar where the wick itself is experience combustion? where is this region?What is fire? Is it matter or is the energy? explain your answer.In a brief paragraph, summary the transforms that a candle undergoes as soon as it burns. Incorporate the following words into the i in a coherent way: wax, wick, phase change, chemistry reaction, vaporize, melt, transforms, solid, liquid, gas, energy, light, and also heat.