Teacher"s Overview

Summary

In this investigation, college student are tested to make cautious observations about a burning candle to uncover the chemical and physical transforms that make it work.

You are watching: Melting candle wax chemical or physical

Objective

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

Safety

Be sure to wear safety goggles when making close observations, tie your hair ago if you have actually long hair, and always be aware of where the fire is with respect to your clothing—do no lean over the flame.Burning candles are open flames the can reason burns. Fluid wax is hot and can cause burns come the skin.

Materials because that Each Group

Tea light candleMatchesSmall beaker or evaporating food (such together 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 can be purchased in large quantities, as can tapered candles from hardware stores. Candle of various colors, sizes, and also shapes have the right to enrich the observations made by the class.


We room all acquainted with burn candles, but how much have we really checked out while looking in ~ one? In this exercise you will certainly be tested to watch a burn candle through the lens that chemistry. You might be surprised by how much is yes, really happening in what seems favor a familiar process!

First we will try to watch details beyond our usual means of looking at a candle, and also then we will certainly look for evidence of the physics or chemistry nature of any changes that room taking place. Take treatment in recording her observations—try to imagine that you have actually never checked out a burning candle before!


Obtain a tea light candle, matches, and any measure 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 amongst many properties to observe: color, texture, mass, physics dimensions, density, aroma… or any type of others you deserve to think of. Usage as plenty of of her physical senses as possible, and be sure to include units for any type of of your quantitative observations.


Use a enhance to carefully light the candle.Repeat the procedure of making qualitative and also quantitative observations of the burning candle, this time making six of each kind of observation. (Some of her observations may relate to properties you have currently recorded, that may be transforming now the the candle is burning.) once again use all your senses to do qualitative observations. Ask you yourself what you can measure because that the quantitative observations.

For her observations and also measurements, consider not just the physics candle, but likewise consider its affect on the wait in the room surrounding it.


Now lay out a in-depth drawing of the burning candle, one enlargement of the part about a centimeter indigenous the optimal of the candle to the topmost tip of the flame:


Label the following regions the the candle in her drawing:

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

Now differentiate as countless different facets of the flame itself and label them in the drawing. Once you have completed recording your observations and also drawings, prepare come blow out the candle, and also be all set to make additional observations together you do this!Blow the end the candle and record 2 qualitative and two quantitative monitorings of the candle automatically after the is extinguished:


Qualitative observationsQuantitative observations
1. 
2. 

Interpreting Evidence


part One

Now the we have actually paid close fist to the properties of a burn candle, we can begin to analyze what we’ve watched in regards to phase changes and also chemical reactions.In a phase change (from hard to fluid or from liquid to gas) the corpuscle of a substance (in this case the molecules of wax) will adjust the setup they have actually with each other. As a solid they will certainly be closely packed together and unable to relocate freely. In the fluid they will have the ability to flow around each other but will still it is in close together, and also as a gas they will certainly fly easily apart but they will certainly still be wax molecules and will have actually the very same structure they had actually as molecule in the solid and also the fluid phases:


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wax from plants and animals have different structures. Below is a molecule comparable to wax— a material that is normally a significant component that the candle wax.

In the boxes below, use small, single shapes come represent whole wax molecules, and sketch their arrangement in the 3 physical phases:


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based upon your observations of the burn candle, did you find evidence because that the readjust from the solid wax phase to the liquid wax phase?


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define this evidence as particularly as possible.


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define this evidence as specifically as possible.


Did you discover evidence for the adjust from the liquid wax step to the gaseous wax phase?


A physics candle is created of wax surrounding a wick. Look up the meaning of the verb “to wick,” and also write the down.Describe the wicking procedure in the burn candle, and also be certain your description consists of the physical state that 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 for this disappearanceIf the wax was just undergoing physical change, would you mean the candle to develop heat and also light as it does when a candle burns?The procedure of burning (as opposed to evaporating) is a chemical reaction, a chemical change. The wax molecules are undergoing a chemical change; they are changing into different molecules by reacting v a problem in the air. What is this problem in the air that a candle requirements to burn?

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

We have the right to represent the combustion of a candle like this:


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finish the following sentence that restates this equation:

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

We space not mindful of oxygen in the air because it is one odorless and colorless gas, and at the temperature the a burn candle, both the CO2 and also the H2O are additionally gases that room invisible come us. We have the right to see proof of chemical change, however, if us restrict the amount of oxygen the is permitted to react v 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 the a tiny beaker or a clear watch glass right into the fire so that the fire touches the surface of the glass. Host it there because that a moment (where that restricts several of the air flow to the flame) and then remove it.

What carry out you watch on the bottom of the beaker? What could this problem be and where did it come from?How go this administer evidence the a chemical reaction is taking place?Wipe the bottom of the manufacturer clean and place an ice cube within it. Host the beaker number of centimeters above (not in) the flame and allow the candle to burn. Have the right to you check out a substance developing on the bottom the the beaker? What can this substance be and also where did that come from? can it have come indigenous the melting ice inside the beaker?Consider the fire itself. Is the fire 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, have the right to you restate that correctly?

Finally, allow us think about the physical phase of the wax together it reacts through the oxygen to create carbon dioxide and also water. Prepare to observe carefully! Blow out the candle and really quickly bring a complement close come the wick. Shot to notice exactly wherein the lit wood splint is with respect to the wick when the candle reignites.

Do this number of times to check out if you observe something interesting. Note any kind of evidence you have actually observed the helps to identify the physical phase of the wax once it reacts v oxygen.

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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 likely to undergo a chemical change?Explain why this is the case based upon your sketches the wax in solid, liquid, and also gas phases.How might this (your prize to question above) explain a authorize that says NO SMOKING close to the pumps in ~ a gas station?Look back at her diagrams that the candle flame. Deserve to you recognize the region where the wick chin is experience combustion? wherein is this region?What is fire? Is it issue or is the energy? describe your answer.In a brief paragraph, summary the transforms that a candle undergoes once it burns. Combine the adhering to words right into the paragraph in a meaningful way: wax, wick, phase change, chemistry reaction, vaporize, melt, transforms, solid, liquid, gas, energy, light, and also heat.