A New Substance Is Produced

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Lesson vi.ane

What is a Chemical Reaction?

Key Concepts:

A concrete alter, such as a land change or dissolving, does not create a new substance, simply a chemic change does.
In a chemical reaction, the atoms and molecules that collaborate with each other are called reactants.
In a chemical reaction, the atoms and molecules produced by the reaction are chosen products.
In a chemical reaction, but the atoms present in the reactants can finish up in the products. No new atoms are created, and no atoms are destroyed.
In a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.

Summary

The teacher will use a small candle flame to demonstrate a chemic reaction between the candle wax and oxygen in the air. Students will see a molecular blitheness of the combustion of methane and oxygen as a model of a like reaction. Students will use atom model cut-outs to model the reaction and see that all the atoms in the reactants prove upward in the products.

Objective

Students will be able to explain that for a chemical reaction to take place, the bonds between atoms in the reactants are broken, the atoms rearrange, and new bonds betwixt the atoms are formed to make the products. Students will also be able to explicate that in a chemic reaction, no atoms are created or destroyed.

Evaluation

Download the educatee activity sheet, and distribute one per student when specified in the activity. The activity sheet will serve as the "Evaluate" component of each 5-East lesson plan.

Safety

Be sure you and the students wearable properly fitting goggles. Be careful when lighting the candle. Be sure that the match and candle are completely extinguished when you are finished with the demonstration.

Materials for the Demonstration

Tea light candle or other small stable candle
Matches
Glass jar, large enough to be placed over the candle

Materials for Each Pupil

Atom cutting-outs from the action sheet
Sheet of colored paper or structure paper
Colored pencils
Scissors
Mucilage or tape

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

Tell students that in previous chapters they take studied different aspects of physical alter. When atoms and molecules speed upwards or slow down, that is a concrete change. When they modify state from liquid to solid or from gas to liquid, that is a physical modify. When a substance is dissolved by h2o or some other solvent, a new substance has non really been formed. The ions or molecules tin still come up back together to form the original substance.

Let students know that in this chapter they will explore what happens during a chemical alter. In a chemical modify, the atoms in the reactants rearrange themselves and bond together differently to grade one or more new products with dissimilar characteristics than the reactants. When a new substance is formed, the change is called a chemical change.
As a demonstration, light a candle and explain what is happening using the terms reactants, products, and chemic reaction.

Explicate that in most chemic reactions, two or more substances, called reactants, collaborate to create unlike substances called products. Tell students that burning a candle is an example of a chemical reaction.

Materials for the Demonstration
- Tea light candle or other small stable candle
- Matches
- Glass jar, large enough to be placed over the candle
Procedure
1. Carefully light a tea calorie-free candle or other small candle.
2. Keep the candle called-for as y'all ask students the questions below. You will put the candle out in the second function of the demonstration.
Expected Results

The wick will grab on fire and the flame will be sustained past the chemical reaction.

The following question is not easy and students are not expected to know the answer at this point. However, thinking about a candle burning in terms of a chemical reaction is a proficient place to start developing what information technology means when substances react chemically.

Ask students:

What do you lot remember are the reactants in this chemic reaction?

Wax and oxygen from the air are the reactants.

Students often say that the string or wick is burning. It is true that the string of the wick does burn down merely it's the wax on the string and not so much the string itself that burns and keeps the candle burning. Explain that the molecules that make up the wax combine with oxygen from the air to brand the products carbon dioxide and water vapor.

Point out to students that this is one of the major characteristics of a chemic reaction: In a chemic reaction, atoms in the reactants combine in new and different ways to class the molecules of the products.

Students may exist surprised that water tin can be produced from combustion. Since nosotros use water to extinguish a fire, it may seem strange that water is actually produced past combustion. You may want to allow students know that when they "fire" food in their bodies, they also produce carbon dioxide and water.
Place a jar over the candle to help students realize that oxygen is a reactant in the burning of a candle.

Remind students that air is a mixture of gases. Explicate that when something burns, it reacts with the oxygen in the air.

Inquire students to make a prediction:

Volition the candle all the same fire if one of the reactants (wax or oxygen) is no longer bachelor?

Students may gauge that the candle will not burn because both reactants are required for the chemical reaction to proceed.

Procedure
1. Carefully place a glass jar over the lit candle.
Expected Results

The flame goes out.

Inquire students:

Why do y'all think the flame goes out when we put a jar over the candle?

Placing a jar over the candle limits the amount of oxygen in the air around the candle. Without enough oxygen to react with the wax, the chemical reaction cannot take place and the candle cannot burn.

When a candle burns for a while, it eventually gets smaller and smaller. Where does the candle wax go?

When a candle burns, the candle wax seems to "disappear." Information technology doesn't actually disappear, though: Information technology reacts chemically, and the new products go into the air.

Note: Some curious students may inquire what the flame is fabricated of. This is a great question and not trivial to answer. The flame is burning wax vapor. The lite of the flame is caused past a process called chemiluminescence. Energy released in the chemic reaction makes electrons from dissimilar molecules move to a higher free energy state. When the electrons come up back downward, free energy is released in the form of light.
Introduce the chemical equation for the combustion of methane and explain that atoms rearrange to become dissimilar molecules.

Explicate to students that wax is made of long molecules chosen methane series and that paraffin is fabricated up of only carbon atoms and hydrogen atoms bonded together. Molecules fabricated of only carbon and hydrogen are called hydrocarbons. Tell students that you lot volition use the simplest hydrocarbon (methane) as a model to show how the wax, or any other hydrocarbon, burns.

Project the image Chemic Reaction between Methane and Oxygen.

Prove students that there is methane and oxygen on the left side of the chemical equation and carbon dioxide and water on the right side. Explicate that the molecules on the left side are the reactants and the ones on the right side are the products. When the candle was called-for, the alkane reacted with oxygen in the air to produce carbon dioxide and water, similar to the chemical reaction between marsh gas and oxygen.

Explain to students that the chemic formula for methane is CH₄. This means that methyl hydride is fabricated up of one carbon atom and iv hydrogen atoms.

Evidence students that the other reactant is two molecules of oxygen gas. Point out that each molecule of oxygen gas is made upwards of two oxygen atoms bonded together. Information technology tin can be confusing for students that oxygen the atom, and oxygen the molecule, are both called oxygen. Permit students know that when nosotros talk about the oxygen in the air, it is always the molecule of oxygen, which is two oxygen atoms bonded together, or O₂.

Enquire students:

Where practise the atoms come from that make the carbon dioxide and the water on the right side of the equation?

The atoms in the products come from the atoms in the reactants. In a chemical reaction, bonds between atoms in the reactants are cleaved and the atoms rearrange and form new bonds to brand the products.

Annotation: Go out this equation projected throughout the activity in the Explore department of this lesson. Students will need to refer to information technology as they model the chemical reaction.

Give Each Educatee an Action Canvass.

Students will tape their observations and answer questions about the activity on the action sail. The Explain Information technology with Atoms and Molecules and Accept Information technology Farther sections of the activity sheet will either be completed as a class, in groups, or individually, depending on your instructions. Look at the teacher version of the activity sheet to notice the questions and answers.
Have students make a model to bear witness that in a chemical reaction the atoms of the reactants rearrange to class the products.

Question to Investigate

Where do the atoms in the products of a chemical reaction come from?

Materials for Each Student
- Atom model cut-outs (carbon, oxygen, and hydrogen)
- Sheet of colored paper or construction newspaper
- Colored pencils
- Scissors
- Mucilage or record
Process
1. Prepare the Atoms
  1. Color the carbon atoms black, the oxygen atoms cerise, and exit the hydrogen atoms white.
  2. Use pair of scissors to carefully cut out the atoms.
2. Build the Reactants
  1. On a canvas of paper, identify the atoms together to make the molecules of the reactants on the left side of the chemic equation for the combustion of marsh gas.
  2. Write the chemic formula under each molecule of the reactants. Likewise draw a + sign between the reactants.
Later on yous are certain that students have made and written the formula for the reactant molecules, tell students that they will rearrange the atoms in the reactants to form the products.
1. Build the Products
  1. Depict an arrow after the 2nd oxygen molecule to testify that a chemic reaction is taking identify.
  2. Rearrange the atoms in the reactants to make the molecules in the products on the right side of the pointer.
  3. Write the chemic formula nether each molecule of the products. Also depict a + sign between the products.
Tell students that in a chemic reaction, the atoms in the reactants come up apart, rearrange, and brand new bonds to form the products.
1. Stand for the Chemic Equation
  1. Have students use their remaining atoms to make the reactants again to represent the chemic reaction every bit a consummate chemical equation.
  2. Glue or tape the atoms to the paper to make a more permanent chemical equation of the combustion of methyl hydride.

Help students count upward the number of atoms on each side of the equation.

Projection the animation Moving Chemical Equation for the Combustion of Methane.

Show students that the atoms in methane and oxygen need to come up apart just like in their models. Besides bespeak out that the atoms arrange themselves differently and bail once again to form new products. This is also like their model. Be sure that students realize that the atoms in the products only come from the reactants. There are no other atoms available. No new atoms are created and no atoms are destroyed.

Explain to students that chemic reactions are more complicated than the simplified model shown in the animation. The animation shows that bonds between atoms in the reactants are broken, and that atoms rearrange and class new bonds to brand the products. In reality, the reactants need to collide and interact with each other in order for their bonds to interruption and rearrange. Also, the animation shows all of the atoms in the reactants coming autonomously and rearranging to form the products. But in many chemical reactions, but some bonds are broken, and groups of atoms stay together every bit the reactants class the products.

Read more than most the combustion of methane in the instructor background section.

Guide students as you reply the post-obit question together:

How many carbon, hydrogen, and oxygen atoms are in the reactants compared to the number of carbon, hydrogen, and oxygen atoms in the products?: Testify students how to use the big number (coefficient) in front of the molecule and the footling number after an atom of the molecule (subscript) to count the atoms on both sides of the equation. Explain to students that the subscript tells how many of a certain type of cantlet are in a molecule. The coefficient tells how many of a item type of molecule there are. And then if there is a coefficient in front of the molecule and a subscript after an atom, you demand to multiply the coefficient times the subscript to become the number of atoms.; For example, in the products of the chemic reaction there are 2H₂O. The coefficient means that there are two molecules of water. The subscript ways that each h2o molecule has two hydrogen atoms. Since each water molecule has 2 hydrogen atoms and in that location are two water molecules, in that location must exist four (ii × two) hydrogen atoms.

Table one. Counting atoms on the reactant and product side of the chemical equation for the combustion of marsh gas.
Atoms	Reactant Side	Product Side
Carbon
Hydrogen
Oxygen

Notation: The coefficients actually betoken the ratios of the numbers of molecules in a chemic reaction. It is not the actual number as in two molecules of oxygen and i molecule of methane since in that location are ordinarily billions of trillions of molecules reacting. The coefficient shows that in that location are twice as many oxygen molecules as methane molecules reacting. It would be right to say that in this reaction there are 2 oxygen molecules for every methane molecule.

Explicate that mass is conserved in a chemic reaction.

Ask students:

Are atoms created or destroyed in a chemical reaction?

No.

How do you know?

There are the same number of each type of cantlet on both the reactant side and the product side of the chemical equation we explored.

In a physical change, similar irresolute country from a solid to a liquid, the substance itself doesn't really alter. How is a chemical modify unlike from a physical change?

In a chemical modify, the molecules in the reactants interact to grade new substances. In a physical alter, like a land alter or dissolving, no new substance is formed.

Explain that some other way to say that no atoms are created or destroyed in a chemical reaction is to say, "Mass is conserved."

Project the image Balanced Equation.

Explain that the balance shows the mass of marsh gas and oxygen on one side exactly equals the mass of carbon dioxide and h2o on the other. When an equation of a chemic reaction is written, it is "balanced" and shows that the atoms in the reactants end upwardly in the products and that no new atoms are created and no atoms are destroyed.
Innovate two other combustion reactions and have students cheque to run across whether or non they are balanced.

Tell students that, in improver to the wax and methyl hydride, some other mutual hydrocarbons are propane (the fuel in outdoor gas grills), and butane (the fuel in disposable lighters). Have students count the number of carbon, hydrogen, and oxygen atoms in the reactants and products of each equation to run across if the equation is balanced. They should record the number of each type of cantlet in the chart on their action sheet.

Lighting an outdoor gas grill—Combustion of propane

C_threeH_eight + 5O_ii → 3CO₂ + 4H_ii0

Using a disposable lighter—Combustion of butane

2C_ivH₁₀ + 13O_ii → 8CO_ii + 10H₂O

After students have counted up each type of atom, review their answers to make sure they know how to translate subscripts and coefficients.