Key Concepts:

A physical change, such together a state readjust or dissolving, go not produce a new substance, yet a chemical adjust does.In a chemistry reaction, the atoms and also molecules that connect with each various other are called reactants.In a chemistry reaction, the atoms and also molecules developed by the reaction are dubbed products. In a chemistry reaction, just the atoms existing in the reactants can finish up in the products. No brand-new atoms room created, and no atoms space destroyed.In a chemical reaction, reactants call each other, bonds in between atoms in the reactants room broken, and atoms rearrange and kind new bonds to do the products.

You are watching: What happens to chemical bonds during chemical reactions?


The teacher will use a little candle fire to show a chemistry reaction in between the candle wax and oxygen in the air. Student will view a molecular animation of the combustion of methane and oxygen together a version of a comparable reaction. Students will usage atom version cut-outs to version the reaction and see the all the atoms in the reactants present up in the products.


Students will have the ability to explain that for a chemistry reaction to take it place, the bonds between atoms in the reactants room broken, the atom rearrange, and new bonds in between the atom are formed to make the products. Students will additionally be maybe to define that in a chemistry reaction, no atom are created or destroyed.


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


Be sure you and the students wear correctly fitting goggles. Be cautious when lighting the candle. Be sure that the match and candle are totally extinguished when you space finished with the demonstration.

Materials for the Demonstration

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

Materials for Each Student

Atom cut-outs from the activity sheetSheet that colored paper or building paperColored pencilsScissorsGlue or tape

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

Tell students that in previous chapters they have actually studied different elements of physics change. As soon as atoms and molecules rate up or slow-moving down, that is a physical change. When they change state from liquid to heavy or from gas come liquid, that is a physics change. When a substance is liquified by water or some other solvent, a new substance has not really been formed. The ions or molecules deserve to still come ago together to form the initial substance.

Let students understand that in this chapter they will check out what happens throughout a chemistry change. In a chemistry change, the atoms in the reaction rearrange themselves and also bond together differently to type one or an ext new products with different qualities than the reactants. Once a brand-new substance is formed, the readjust is called a chemistry change.

As a demonstration, irradiate a candle and also explain what is happening using the terms reactants, products, and chemical reaction.

Explain that in many chemical reactions, 2 or more substances, dubbed reactants, communicate to produce different substances dubbed products. Tell students the burning a candle is an instance of a chemistry reaction.

Materials because that the Demonstration

Tea irradiate candle or other little stable candle MatchesGlass jar, huge enough to be inserted over the candle


Carefully light a tea irradiate candle or other small candle.Keep the candle burning as you ask student the questions below. Girlfriend will put the candle out in the second component of the demonstration.

Expected results

The wick will catch on fire and the flame will be sustained by the chemistry reaction.

The complying with question is not easy and students room not intended to understand the answer in ~ this point. However, thinking about a candle burning in regards to a chemical reaction is a good place come start arising what it means when substances reaction chemically.

Ask students:

What perform you think are the reaction in this chemical reaction? Wax and oxygen from the air space the reactants.

Students frequently say the the cable or wick is burning. That is true the the string of the wick does burn but it’s the wax on the string and not so lot the string itself that burns and keeps the candle burning. Define that the molecules that make up the wax integrate with oxygen indigenous the waiting to make the commodities carbon dioxide and also water vapor.

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

Students may be surprised the water deserve to be created from combustion. Due to the fact that we usage water come extinguish a fire, it might seem strange the water is actually created by combustion. You might want to let students know that when they “burn” food in their bodies, they also produce carbon dioxide and water.

Place a jar end the candle to help students realize the oxygen is a reactant in the burn of a candle.

Remind students the air is a mixture the gases. Explain that as soon as something burns, the reacts v the oxygen in the air.

Ask student to make a prediction:

Will the candle still burn if among the reactants (wax or oxygen) is no much longer available? Students may guess that the candle will not burn due to the fact that both reactants are compelled for the chemistry reaction to continue.


Carefully location a glass jar end the lit candle.


Expected Results

The flame goes out.

Ask students:

Why execute you think the flame goes out as soon as we placed a jar end the candle? put a jar end the candle limits the amount of oxygen in the air roughly the candle. Without sufficient oxygen to react v the wax, the chemical reaction cannot take it place and also the candle can not burn. Once a candle burns because that a while, it at some point gets smaller and also smaller. Where does the candle wax go? when a candle burns, the candle wax seems to “disappear.” that doesn’t yes, really disappear, though: It reaction chemically, and also the new products go into the air.

Note: part curious students may ask what the flame is make of. This is a good question and also not trivial to answer. The flame is burn wax vapor. The light of the flame is resulted in by a procedure called chemiluminescence. Energy released in the chemical reaction renders electrons from various molecules move to a higher energy state. Once the electrons come ago down, power is released in the form of light.


Have students do a design to display that in a chemical reaction the atom of the reaction rearrange to type the products.

Question to Investigate

Where execute the atoms in the commodities of a chemistry reaction come from?

Materials because that Each Student

Atom design cut-outs (carbon, oxygen, and also hydrogen)Sheet that colored document or construction paperColored pencilsScissorsGlue or tape


Prepare the AtomsColor the carbon atoms black, the oxygen atoms red, and leave the hydrogen atom white. Use scissors to carefully cut the end the atoms.Build the Reactants

On a sheet of paper, place the atoms together to make the molecules of the reaction on the left next of the chemistry equation for the burning of methane.

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

After you room sure that students have made and written the formula for the reactant molecules, phone call students that they will certainly rearrange the atoms in the reaction to type the products.

Build the ProductsDraw an arrow after the second oxygen molecule to display that a chemistry reaction is acquisition place.Rearrange the atoms in the reaction to make the molecule in the commodities on the appropriate side that the arrow. Compose the chemical formula under each molecule of the products. Likewise draw a + sign in between the products.

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

Represent the chemistry EquationHave students usage their continuing to be atoms to make the reactants again to represent the chemistry reaction together a complete chemical equation. Adhesive or ice the atom to the document to do a an ext permanent chemistry equation of the burning of methane.Extend

Introduce two other combustion reactions and also have students examine to view whether or no they are balanced.

Tell student that, in enhancement to the wax and also methane, some other common hydrocarbons space propane (the fuel in out gas grills), and also butane (the fuel in disposable lighters). Have students count the number of carbon, hydrogen, and also oxygen atom in the reactants and also products of every equation to see if the equation is balanced. They should record the number of each form of atom in the graph on their activity sheet.

See more: How Many Kg Is 175 Pounds To Kg, 175 Lb To Kg


Lighting an outdoor gas grill—Combustion the propane

C3H8 + 5O2 → 3CO2 + 4H20

Using a disposable lighter—Combustion of butane

2C4H10 + 13O2 → 8CO2 + 10H2O

After students have counted increase each kind of atom, evaluation their answers come make certain they know exactly how to analyze subscripts and also coefficients.