Key Concepts:

A physical change, such as a state change or dissolving, walk not create a new substance, but a chemical adjust does.In a chemical reaction, the atoms and also molecules that interact with each various other are called reactants.In a chemistry reaction, the atoms and molecules created by the reaction are called products. In a chemistry reaction, just the atoms present in the reaction can end up in the products. No brand-new atoms room created, and also no atoms room destroyed.In a chemistry reaction, reactants call each other, bonds between atoms in the reactants room broken, and atoms rearrange and form new bond to make the products.

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The teacher will usage a tiny candle flame to demonstrate a chemical reaction in between the candle wax and oxygen in the air. College student will view a molecular computer animation of the combustion of methane and oxygen together a model of a comparable reaction. Students will usage atom model cut-outs to model the reaction and see the all the atom in the reactants show up in the products.


Students will be able to explain the for a chemical reaction to take place, the bonds between atoms in the reactants room broken, the atoms rearrange, and brand-new bonds in between the atoms are formed to make the products. Student will also be able to define that in a chemical reaction, no atoms are developed or destroyed.


Download the student activity sheet, and also distribute one every student once specified in the activity. The activity sheet will serve together the “Evaluate” component of every 5-E great plan.


Be sure you and also the students wear appropriately fitting goggles. Be careful when bright the candle. Be sure that the match and candle are totally extinguished when you space finished v the demonstration.

Materials for the Demonstration

Tea irradiate candle or other tiny stable candle MatchesGlass jar, big enough to be put over the candle

Materials for Each Student

Atom cut-outs native the activity sheetSheet the colored file or construction paperColored pencilsScissorsGlue or tape

Review what happens throughout a physical readjust and introduce the idea of chemistry change.

Tell students the in ahead chapters they have actually studied different aspects of physics change. As soon as atoms and also molecules rate up or slow down, that is a physical change. When they adjust state from fluid to hard or native gas to liquid, the is a physical change. Once a substance is liquified by water or some other solvent, a new substance has actually not really been formed. The ions or molecules have the right to still come ago together to form the initial substance.

Let students understand that in this thing they will check out what happens throughout a chemical change. In a chemical change, the atoms in the reaction rearrange themselves and also bond together differently to type one or an ext new assets with different attributes than the reactants. When a new substance is formed, the readjust is referred to as a chemistry change.

As a demonstration, light a candle and explain what is happening using the state reactants, products, and chemical reaction.

Explain that in many chemical reactions, two or more substances, called reactants, connect to create different substances dubbed products. Phone call students the burning a candle is an example of a chemistry reaction.

Materials for the Demonstration

Tea light candle or other tiny stable candle MatchesGlass jar, big enough to be put over the candle


Carefully irradiate a tea irradiate candle or other little candle.Keep the candle burning as you ask student the concerns below. You will placed the candle the end in the second part of the demonstration.

Expected results

The wick will record on fire and the flame will be sustained by the chemical reaction.

The following question is not easy and students are not intended to understand the answer in ~ this point. However, thinking around a candle burn in terms of a chemical reaction is a an excellent place to start occurring what it means when substances react chemically.

Ask students:

What carry out you think space the reactants in this chemistry reaction? Wax and oxygen from the air room the reactants.

Students frequently say the the cable or wick is burning. It is true the the string of the wick does burn however it’s the wax ~ above the string and not so lot the string itself the burns and also keeps the candle burning. Describe that the molecules that make up the wax integrate with oxygen native the waiting to do the products carbon dioxide and water vapor.

Point out to students the this is one of the significant characteristics of a chemistry reaction: In a chemical reaction, atoms in the reactants integrate in new and various ways to type the molecules of the products.

Students might be surprised that water deserve to be produced from combustion. Because we use water to extinguish a fire, it might seem strange the water is actually produced by combustion. You might want come let students know that as soon as they “burn” food in your bodies, they additionally produce carbon dioxide and also water.

Place a jar end the candle to aid students realize the oxygen is a reactant in the burning of a candle.

Remind students the air is a mixture that gases. Describe that once something burns, that reacts with the oxygen in the air.

Ask student to do a prediction:

Will the candle quiet burn if among the reaction (wax or oxygen) is no longer available? Students may guess the the candle will not burn since both reactants are forced for the chemistry reaction to continue.


Carefully location a glass jar end the lit candle.


Expected Results

The fire goes out.

Ask students:

Why perform you think the fire goes out as soon as we placed a jar over the candle? place a jar end the candle boundaries the quantity of oxygen in the air roughly the candle. Without enough oxygen come react with the wax, the chemical reaction cannot take place and also the candle cannot burn. Once a candle burns for a while, it at some point gets smaller and smaller. Whereby does the candle wax go? as soon as a candle burns, the candle wax appears to “disappear.” that doesn’t really disappear, though: It reaction chemically, and the new products enter the air.

Note: some curious students might ask what the flame is do of. This is a an excellent question and also not trivial to answer. The flame is burning wax vapor. The irradiate of the fire is caused by a procedure called chemiluminescence. Power released in the chemistry reaction makes electrons from various molecules relocate to a greater energy state. As soon as the electron come ago down, energy is exit in the type of light.


Have students make a design to show that in a chemical reaction the atom of the reactants rearrange to type the products.

Question come Investigate

Where perform the atom in the commodities of a chemical reaction come from?

Materials because that Each Student

Atom model cut-outs (carbon, oxygen, and hydrogen)Sheet of colored paper or building paperColored pencilsScissorsGlue or tape


Prepare the AtomsColor the carbon atom black, the oxygen atoms red, and leave the hydrogen atom white. Usage scissors to closely cut out the atoms.Build the Reactants

On a paper of paper, location the atoms together to make the molecules of the reaction on the left side of the chemical equation for the combustion of methane.

Write the chemical formula under each molecule that the reactants. Additionally draw a + sign between the reactants.

After you are sure that students have made and also written the formula because that the reactant molecules, call students that they will rearrange the atom in the reaction to kind the products.

Build the ProductsDraw an arrow after the second oxygen molecule to show that a chemical reaction is taking place.Rearrange the atoms in the reaction to make the molecule in the assets on the right side the the arrow. Compose the chemical formula under every molecule of the products. Also draw a + sign between the products.

Tell students the in a chemical reaction, the atoms in the reaction come apart, rearrange, and make brand-new bonds to type the products.

Represent the chemistry EquationHave students usage their staying atoms to do the reaction again to stand for the chemistry reaction together a complete chemical equation. Adhesive or ice the atoms to the document to make a an ext permanent chemistry equation the the combustion of methane.Extend

Introduce 2 other combustion reactions and have students inspect to see whether or not they room balanced.

Tell students that, in addition to the wax and also methane, some other usual hydrocarbons space propane (the fuel in the end gas grills), and also butane (the fuel in disposable lighters). Have actually students count the number of carbon, hydrogen, and oxygen atom in the reactants and products of every equation to watch if the equation is balanced. They should record the number of each kind of atom in the chart on their activity sheet.

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Lighting an out gas grill—Combustion that propane

C3H8 + 5O2 → 3CO2 + 4H20

Using a disposable lighter—Combustion that butane

2C4H10 + 13O2 → 8CO2 + 10H2O

After students have actually counted increase each kind of atom, testimonial their answers come make certain they know just how to interpret subscripts and also coefficients.