Lesson Plan
Chemical Reactions
Context
A chemical reaction involves the breaking and reforming of chemical bonds to create new substances. Every reaction
involves energy and must express the conservation of mass. Chemical reactions are important in everyday life.
Understanding the energy and equilibrium of reactions is important in industry.
Essential Questions
￮￮ What is a chemical reaction?
￮￮ How can the conservation of mass during a reaction be demonstrated?
￮￮ What are the different types of reactions and how can their products be predicted?
￮￮ How does the periodic table help predict the reactivity of elements?
￮￮ How is energy involved in a chemical reaction?
￮￮ What is chemical equilibrium?
￮￮ How is equilibrium impacted by temperature and concentration of reactants and products?
Enduring Understandings
￮￮ A chemical reaction is the breaking and forming of chemical bonds to produce new substances.
￮￮ Chemical reactions can be expressed as equations. These demonstrate the law of conservation of mass by showing
an equal number of atoms of each element in the reactants and products.
￮￮ Chemical reactions can be classified by type, which helps to predict products. They can also be classified by energy
loss or gain.
￮￮ The ordering of the elements on the periodic table reflects trends in reactivity.
￮￮ Chemical equilibrium is reached when the rate of a forward reaction equals the rate of a reverse reaction.
￮￮ The equilibrium of a chemical reaction can be manipulated to maximize the amount of products made.
Time
Three to four 50-minute class periods
Grade Level
Grades 9–12
Differentiation
Activities can be completed as one class group or can be assigned to individuals, small groups, or pairs according to
ability and skill levels.
Materials
￮￮ Rosen Digital’s Core Concepts: Chemistry database
￮￮ Water
￮￮ Ammonium chloride
￮￮ Steel wool
￮￮ Vinegar
￮￮ Beakers
￮￮ Styrofoam coffee cups
￮￮ Thermometers
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Lesson Plan (cont.)
Chemical Reactions
￮￮ Scales
￮￮ Graduated cylinders
￮￮ Calculators
Student Learning Objectives
￮￮ Students will be able to balance chemical reactions and calculate simple mole conversions to demonstrate the
conservation of mass.
￮￮ Students will be able to identify different types of chemical reactions.
￮￮ Students will use the type of reaction and the periodic table to predict the products of reactions.
￮￮ Students will describe the energy associated with a reaction and whether it is absorbed or released.
￮￮ Students will define chemical equilibrium.
￮￮ Students will predict the effect of temperature and concentration changes on chemical reactions.
Next Generation Science Standards Addressed
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HS-PS1-2.
Construct and revise an explanation for the outcome of a simple chemical reaction
based on the outermost electron states of atoms, trends in the periodic table, and
knowledge of the patterns of chemical properties. [Clarification Statement: Examples of
chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen,
or of carbon and hydrogen.] [Assessment Boundary: Assessment is limited to chemical
reactions involving main group elements and combustion reactions.]
HS-PS1-4.
Develop a model to illustrate that the release or absorption of energy from a
chemical reaction system depends upon the changes in total bond energy.
[Clarification Statement: Emphasis is on the idea that a chemical reaction is a system that
affects the energy change. Examples of models could include molecular-level drawings and
diagrams of reactions, graphs showing the relative energies of reactants and products, and
representations showing energy is conserved.] [Assessment Boundary: Assessment does
not include calculating the total bond energy changes during a chemical reaction from the
bond energies of reactants and products.]
HS-PS1-5.
Apply scientific principles and evidence to provide an explanation about the effects
of changing the temperature or concentration of the reacting particles on the rate
at which a reaction occurs. [Clarification Statement: Emphasis is on student reasoning
that focuses on the number and energy of collisions between molecules.] [Assessment
Boundary: Assessment is limited to simple reactions in which there are only two
reactants; evidence from temperature, concentration, and rate data; and qualitative
relationships between rate and temperature.]
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Chemical Reactions
HS-PS1-6.
Refine the design of a chemical system by specifying a change in conditions
that would produce increased amounts of products at equilibrium.* [Clarification
Statement: Emphasis is on the application of Le Chatelier’s Principle and on refining
designs of chemical reaction systems, including descriptions of the connection between
changes made at the macroscopic level and what happens at the molecular level. Examples
of designs could include different ways to increase product formation including adding
reactants or removing products.] [Assessment Boundary: Assessment is limited to
specifying the change in only one variable at a time. Assessment does not include
calculating equilibrium constants and concentrations.]
HS-PS1-7.
Use mathematical representations to support the claim that atoms, and therefore
mass, are conserved during a chemical reaction. [Clarification Statement: Emphasis is
on using mathematical ideas to communicate the proportional relationships between masses
of atoms in the reactants and the products, and the translation of these relationships to the
macroscopic scale using the mole as the conversion from the atomic to the macroscopic
scale. Emphasis is on assessing students’ use of mathematical thinking and not on
memorization and rote application of problem-solving techniques.] [Assessment Boundary:
Assessment does not include complex chemical reactions.]
NGSS Science and Engineering Practices Addressed
￮￮ Developing and Using Models
￮￮ Using Mathematics and Computational Thinking
￮￮ Constructing Explanations and Designing Solutions
NGSS Crosscutting Concepts Addressed
Patterns: Different patterns may be observed at each of the scales at which a system is studied and can provide
evidence for causality in explanations of phenomena. (HS-PS1-2), (HS-PS1-5)
Energy and Matter: The total amount of energy and matter in closed systems is conserved. (HS-PS1-7) Changes
of energy and matter in a system can be described in terms of energy and matter flows into, out of, and within that
system. (HS-PS1-4)
Stability and Change: Much of science deals with constructing explanations of how things change and how they
remain stable. (HS-PS1-6)
Scientific Knowledge Assumes an Order and Consistency in Natural Systems: Science assumes the universe
is a vast single system in which basic laws are consistent. (HS-PS1-7)
Common Core ELA Standards Addressed
WHST.9-12.7
Conduct short as well as more sustained research projects to answer a question (including a self-generated
question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize multiple sources on the
subject, demonstrating understanding of the subject under investigation. (HS-PS1-6)
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Chemical Reactions
Common Core Mathematics Standards Addressed
MP.2
Reason abstractly and quantitatively. (HS-PS1-5), (HS-PS1-7)
MP.4
Model with mathematics. (HS-PS1-4)
Introduction
1. Ask students to read the Core Concepts: Chemistry article Chemical Reaction Basics.
2. Discuss the reading with guiding questions.
a. What is a chemical reaction?
b. What is the difference between a reactant and a product?
c. How is energy involved in a chemical reaction?
d. What are some forms of energy?
e. How is the periodic table important to describing chemical reactions?
The Periodic Table and Reactivity
1. Begin the discussion of the reactivity of elements with the noble gases. Direct students to use the Core Concepts:
Chemistry database to explore the noble gases independently or in pairs. Ask students to find out everything they can
about these elements and to record their findings.
2. Once students have completed their research, ask what they found. Create a list of properties together.
3. Guide the discussion toward the number of valence electrons in the noble gases and why this makes them unreactive.
a. Having eight valence electrons is a stable configuration.
b. All other elements react in such a way as to gain eight valence electrons to achieve this stability.
c. Point out the exceptions, such as hydrogen or helium, which only need two valence electrons to be stable.
d. Using the Periodic Table Reference Guide, show students how to determine the number of valence electrons the
elements in groups 1, 2, and 13 through 18 have.
4. Use examples to illustrate how elements react with each other to create compounds that give them stable electron
configurations. Demonstrate for the students, using these element combinations, how to draw Lewis dot diagrams. Show
that each bond includes two shared electrons for a covalent bond. For ionic bonds, show that electrons are transferred and
charges formed on the atoms to create ions. Include dot diagrams of one or two noble gases to demonstrate that these
atoms are already stable and will not react.
a. Sodium and chlorine
b. Magnesium and oxygen
c. Hydrogen and nitrogen
5. Ask students to create three of their own element combinations and dot diagrams.
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Chemical Reactions
Balancing Reactions
1. Guide students through one round of the Chemical Reactions: Moving Molecules activity.
a. Select hydrogen first
b. Add chlorine
c. Add magnesium
d. Add nitrogen
e. Balance the final equations together as a class and explain how this demonstrates the conservation of mass.
2. Ask the students to start the activity over and make their own choices to explore the possible reactions. Each student
should complete two full sets of four balanced equations. Students can print, email, or save their activity results as a PDF.
Types of Reactions
1. Introduce the types of chemical reactions including combination, decomposition, single replacement, double replacement,
and combustion. Write out balanced equations to show examples of each type. Examples could include:
a. Combination – hydrogen gas and oxygen gas to produce water
b. Decomposition – mercury (II) oxide to produce liquid mercury and oxygen gas
c. Single replacement – magnesium and silver nitrate to produce silver and magnesium nitrate
d. Double replacement – barium chloride and potassium carbonate to produce solid barium carbonate and potassium
chloride
e. Combustion – methane gas and oxygen gas to produce carbon dioxide gas and water vapor
2. Ask the students to go through their completed Chemical Reactions: Moving Molecules results to identify the different
types of reactions they created and balanced.
Energy of Reactions
1. Begin the discussion of energy by defining endothermic and exothermic.
a. endothermic – the reaction takes in energy; the surroundings become cooler
b. exothermic – the reaction gives off energy; the surroundings become warmer
2. Demonstrate an example of each type of reaction and allow students to observe the temperature change.
a. Demonstrate an endothermic reaction by dissolving ammonium chloride in water. The container should become cooler.
b. Demonstrate an exothermic reaction by soaking steel wool in vinegar to start the rusting process. The container should
become warmer.
c. Use a thermometer in each demonstration to show students that heat is absorbed or released.
Chemical Equilibrium
1. Ask students to read the Core Concepts: Chemistry section Understanding Equilibrium.
￮￮ Define equilibrium as a point a reaction reaches when the rate of the forward reaction equals the rate of the
reverse reaction.
￮￮ Address a common misconception: Equilibrium does not mean that the amounts of reactants and products are
equal to each other. It means that the amounts remain constant.
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2. Use the Haber process as an example of trying to optimize a reaction to get as much product as possible. Discuss the
ways in which the reaction can be optimized in terms of Le Châtelier’s Principle.
a. Changing the temperature.
i. The forward reaction is exothermic.
ii. Increasing the temperature will cause the reaction to shift to the left, making more reactant.
iii. Decreasing the temperature will cause the reaction to the right, making more product.
b. Changing the concentration of the reactants or products.
i. Adding more reactants will shift the reaction to the right.
ii. Adding more products will shift the reaction to the left.
iii. Removing reactants will shift the reaction to the left.
iv. Removing products will shift the reaction to the right.
c. Changing pressure
i. Increasing pressure will shift the reaction to the right.
ii. Decreasing pressure will shift the reaction to the left.
3. Give students other examples of reactions and ask them to predict what shifts will occur with the above changes in
temperature, concentration, and pressure.
a. 2SO2 (g) + O2 (g) ↔ 2SO3 ( g); exothermic
b. PCl5 (g) ↔ PCl3 (g) + Cl2 ( g ); endothermic
Extension
1. Ask students to read section Heats of Reaction and perform the Try This! activity Calorimeters Made of Coffee Cups.
Ask students to discuss how a calorimeter works.
2. Ask students to design an experiment to use a calorimeter to measure the energy of a reaction between vinegar and
baking soda.
3. Discuss the calculations and measurements involved:
a. Measure the volume (about a quarter cup) of vinegar and measure or calculate its mass, assuming a density of
1.0 g/mL.
b. Calculate the number of moles of vinegar. (Vinegar is 5 percent acetic acid)
c. Measure the mass of baking soda (about one teaspoon) and calculate the number of moles.
d. Measure initial and final temperatures of the vinegar and reaction mixture to calculate the temperature change of the
reaction.
e. Measure the volume of the solution and calculate its mass, assuming a density of 1.0 g/mL.
f. Calculate the heat of reaction. ∆H = m x C x DT (C = specific heat capacity of water = 4.18 J/g x °C)
4. The experimental design should include:
a. Materials list
b. Procedure
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Chemical Reactions
c. Calorimeter design
d. Data collection
e. Calculations
f. Analysis
5. Each experiment should be approved by the teacher before it can be conducted by the students.
6. Guide students through the calculations if necessary.
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