what happens to the atoms during a chemical reaction

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Lesson 6.1

What is a Chemic Reaction?

Key Concepts:

• A physical alter, such as a state change or dissolving, does not create a new substance, but a chemical alter does.
• In a chemical reaction, the atoms and molecules that interact with each other are called reactants.
• In a chemical reaction, the atoms and molecules produced past the reaction are chosen products.
• In a chemical reaction, only the atoms present in the reactants can end upwards in the products. No new atoms are created, and no atoms are destroyed.
• In a chemic 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-scale candle flame to demonstrate a chemical reaction betwixt the candle wax and oxygen in the air. Students will see a molecular blitheness of the combustion of marsh gas and oxygen every bit a model of a similar reaction. Students will use atom model cut-outs to model the reaction and see that all the atoms in the reactants show up in the products.

Objective

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

Evaluation

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

Prophylactic

Be sure you and the students vesture properly plumbing fixtures goggles. Exist conscientious when lighting the candle. Be sure that the friction match and candle are completely extinguished when you are finished with the sit-in.

Materials for the Demonstration

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

Materials for Each Student

• Atom cut-outs from the activity canvass
• Sheet of colored paper or structure newspaper
• Colored pencils
• Scissors
• Glue or record

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

   Tell students that in previous capacity they have studied unlike aspects of physical change. When atoms and molecules speed upwards or wearisome down, that is a physical change. When they change state from liquid to solid or from gas to liquid, that is a physical alter. When a substance is dissolved by water or some other solvent, a new substance has not really been formed. The ions or molecules tin can still come back together to form the original substance.

   Allow students know that in this chapter they will explore what happens during a chemic change. In a chemical alter, the atoms in the reactants rearrange themselves and bond together differently to form ane or more new products with unlike characteristics than the reactants. When a new substance is formed, the change is called a chemical change.

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

   Explain that in near chemical reactions, two or more substances, called reactants, collaborate to create different substances called products. Tell students that burning a candle is an case of a chemic reaction.

   Materials for the Demonstration

   • Tea low-cal candle or other small stable candle
   • Matches
   • Drinking glass jar, large plenty to be placed over the candle

   Process

   1. Carefully light a tea light candle or other small candle.
   2. Go on the candle burning as yous ask students the questions beneath. You will put the candle out in the 2d office of the sit-in.

   Expected Results

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

   The following question is not easy and students are not expected to know the reply at this point. However, thinking most a candle called-for in terms of a chemical reaction is a good place to starting time developing what it means when substances react chemically.

   Ask students:

   What do you think are the reactants in this chemical reaction?

   Wax and oxygen from the air are the reactants.

   Students oft say that the string or wick is burning. Information technology is true that the string of the wick does burn but it'south the wax on the cord and not and then 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 make the products carbon dioxide and water vapor.

   Signal out to students that this is one of the major characteristics of a chemical reaction: In a chemical reaction, atoms in the reactants combine in new and different means to form the molecules of the products.

   Students may be surprised that water can be produced from combustion. Since we use h2o to extinguish a fire, information technology may seem strange that h2o is actually produced by combustion. You lot may want to permit students know that when they "burn" nutrient in their bodies, they also produce carbon dioxide and h2o.

3. 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. Explain that when something burns, it reacts with the oxygen in the air.

   Ask students to make a prediction:

   Will the candle nonetheless burn if i of the reactants (wax or oxygen) is no longer available?

   Students may guess that the candle volition not burn because both reactants are required for the chemical reaction to keep.

   Procedure

   1. Carefully place a glass jar over the lit candle.

      

   Expected Results

   The flame goes out.

   Ask students:

   Why do you 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." It doesn't really disappear, though: It reacts chemically, and the new products become into the air.

   Note: Some curious students may ask what the flame is made of. This is a smashing question and not lilliputian to answer. The flame is burning wax vapor. The calorie-free of the flame is caused by a procedure chosen chemiluminescence. Free energy released in the chemic reaction makes electrons from dissimilar molecules movement to a higher energy country. When the electrons come dorsum down, free energy is released in the class of lite.

4. Introduce the chemic equation for the combustion of methane and explicate that atoms rearrange to become dissimilar molecules.

   Explain to students that wax is made of long molecules called alkane series and that methane series is made up of simply carbon atoms and hydrogen atoms bonded together. Molecules fabricated of simply carbon and hydrogen are chosen hydrocarbons. Tell students that you will use the simplest hydrocarbon (methane) every bit a model to show how the wax, or any other hydrocarbon, burns.

   Project the image Chemical Reaction between Methane and Oxygen.

   Show students that there is methane and oxygen on the left side of the chemical equation and carbon dioxide and water on the correct side. Explain that the molecules on the left side are the reactants and the ones on the correct side are the products. When the candle was burning, the paraffin reacted with oxygen in the air to produce carbon dioxide and water, similar to the chemical reaction between marsh gas and oxygen.

   Explicate to students that the chemical formula for methane is CH₄. This means that marsh gas is fabricated up of ane carbon atom and four hydrogen atoms.

   Evidence students that the other reactant is 2 molecules of oxygen gas. Point out that each molecule of oxygen gas is made up of two oxygen atoms bonded together. It can be disruptive for students that oxygen the atom, and oxygen the molecule, are both called oxygen. Allow students know that when we talk about the oxygen in the air, it is always the molecule of oxygen, which is two oxygen atoms bonded together, or O₂.

   Ask students:

   Where do 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 broken and the atoms rearrange and form new bonds to make the products.

   Notation: Leave this equation projected throughout the activity in the Explore section of this lesson. Students volition need to refer to it as they model the chemical reaction.

   Give Each Student an Activity Canvass.

   Students will record their observations and answer questions nigh the activity on the action canvas. The Explicate It with Atoms and Molecules and Take Information technology Farther sections of the action canvass will either be completed as a form, in groups, or individually, depending on your instructions. Look at the instructor version of the activity sail to find the questions and answers.

5. Accept students make a model to show that in a chemical reaction the atoms of the reactants rearrange to form the products.

   Question to Investigate

   Where practise the atoms in the products of a chemic reaction come from?

   Materials for Each Student

   • Atom model cut-outs (carbon, oxygen, and hydrogen)
   • Sheet of colored paper or construction paper
   • Colored pencils
   • Pair of scissors
   • Glue or record

   Procedure

   1. Prepare the Atoms

      1. Colour the carbon atoms black, the oxygen atoms cherry, and leave the hydrogen atoms white.
      2. Apply pair of scissors to advisedly cut out the atoms.

   2. Build the Reactants

      1. On a sheet of newspaper, place the atoms together to make the molecules of the reactants on the left side of the chemic equation for the combustion of methane.

         
      2. Write the chemical formula nether each molecule of the reactants. Too draw a + sign betwixt the reactants.

   Later you are sure that students take fabricated and written the formula for the reactant molecules, tell students that they will rearrange the atoms in the reactants to course the products.

   1. Build the Products

      1. Draw an arrow afterward the second oxygen molecule to show that a chemical reaction is taking place.
      2. Rearrange the atoms in the reactants to brand the molecules in the products on the correct side of the arrow.
      3. Write the chemical formula under each molecule of the products. Also draw a + sign between the products.

   Tell students that in a chemical reaction, the atoms in the reactants come autonomously, rearrange, and make new bonds to course the products.

   1. Represent the Chemical Equation

      1. Have students use their remaining atoms to make the reactants again to represent the chemic reaction as a complete chemic equation.
      2. Glue or tape the atoms to the paper to brand a more permanent chemic equation of the combustion of methane.

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

   Project the blitheness Moving Chemical Equation for the Combustion of Methane.

   Evidence students that the atoms in methyl hydride and oxygen demand to come apart just similar in their models. Also indicate out that the atoms conform themselves differently and bail once again to form new products. This is also similar their model. Be certain 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 chemical reactions are more complicated than the simplified model shown in the blitheness. The animation shows that bonds between atoms in the reactants are broken, and that atoms rearrange and form new bonds to make the products. In reality, the reactants need to collide and interact with each other in lodge for their bonds to break and rearrange. Too, the animation shows all of the atoms in the reactants coming autonomously and rearranging to grade the products. But in many chemical reactions, only some bonds are broken, and groups of atoms stay together as the reactants course the products.

   Read more than about the combustion of methane in the teacher background section.

   Guide students equally you answer the following 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?

   Show students how to apply the big number (coefficient) in front of the molecule and the little 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 sure blazon of atom are in a molecule. The coefficient tells how many of a particular type of molecule there are. So if there is a coefficient in front end of the molecule and a subscript after an atom, you demand to multiply the coefficient times the subscript to get the number of atoms.

   For example, in the products of the chemical reaction there are 2H₂O. The coefficient means that at that place are two molecules of water. The subscript means that each water molecule has 2 hydrogen atoms. Since each water molecule has two hydrogen atoms and there are two water molecules, in that location must be 4 (two × 2) hydrogen atoms.

   Table one. Counting atoms on the reactant and production side of the chemical equation for the combustion of methane.

   Atoms	Reactant Side	Production Side
   Carbon
   Hydrogen
   Oxygen

   Notation: The coefficients actually betoken the ratios of the numbers of molecules in a chemic reaction. It is not the bodily number equally in two molecules of oxygen and one molecule of methyl hydride since there are usually billions of trillions of molecules reacting. The coefficient shows that there are twice as many oxygen molecules as methane molecules reacting. Information technology would be right to say that in this reaction there are two oxygen molecules for every marsh gas molecule.

7. Explain that mass is conserved in a chemical reaction.

   Ask students:

   Are atoms created or destroyed in a chemical reaction?

   No.

   How do you lot know?

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

   In a concrete change, similar changing state from a solid to a liquid, the substance itself doesn't really alter. How is a chemic change different from a physical alter?

   In a chemic alter, the molecules in the reactants collaborate to form new substances. In a physical change, like a state modify or dissolving, no new substance is formed.

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

   Project the image Counterbalanced Equation.

   Explain that the balance shows the mass of methane and oxygen on one side exactly equals the mass of carbon dioxide and water on the other. When an equation of a chemical reaction is written, it is "balanced" and shows that the atoms in the reactants end upwards in the products and that no new atoms are created and no atoms are destroyed.

8. Introduce ii other combustion reactions and accept students bank check to see whether or not they are balanced.

   Tell students that, in add-on to the wax and methane, some other common hydrocarbons are propane (the fuel in outdoor gas grills), and butane (the fuel in dispensable lighters). Have students count the number of carbon, hydrogen, and oxygen atoms in the reactants and products of each equation to see if the equation is balanced. They should record the number of each type of atom in the chart on their activity sheet.

   

   Lighting an outdoor gas grill—Combustion of propane

   C₃H₈ + 5O_two → 3CO₂ + 4H₂0

   Using a dispensable lighter—Combustion of butane

   2C₄H_ten + 13O₂ → 8CO₂ + 10H₂O

   Afterwards students have counted up each type of cantlet, review their answers to make sure they know how to interpret subscripts and coefficients.

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Source: https://www.middleschoolchemistry.com/lessonplans/chapter6/lesson1

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