ALEX Lesson Plan


S'mores - Limiting & Excess Reactants (Reagents)

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  This lesson provided by:  
Author:Brenda Rinehart
System: Shelby County
School: Shelby County Board Of Education
  General Lesson Information  
Lesson Plan ID: 26267


S'mores - Limiting & Excess Reactants (Reagents)


Students will use manipulatives that represent the ingredients for S'mores (graham crackers, marshmallows, chocolate bar) to determine the limiting and excess reactants (reagents) for making S'mores. The students will extend this to preparing hot dogs for guests at a party and then relate the concept to an actual chemical reaction.
This lesson is modified from a lesson by Rick Moog (POGIL project) and in cooperation with Michelle Holdbrooks at Thompson High School.

This lesson plan was created as a result of the Girls Engaged in Math and Science University, GEMS-U Project.

 Associated Standards and Objectives 
Content Standard(s):
SC (9-12) Chemistry
6. Solve stoichiometric problems involving relationships among the number of particles, moles, and masses of reactants and products in a chemical reaction.
  • Predicting ionic and covalent bond types and products given known reactants
  • Assigning oxidation numbers for individual atoms of monatomic and polyatomic ions
  • Identifying the nomenclature of ionic compounds, binary compounds, and acids
  • Classifying chemical reactions as composition, decomposition, single replacement, or double replacement
  • Determining the empirical or molecular formula for a compound using percent composition data
  • SC2015 (9-12) Physical Science
    5. Use mathematical representations to support and verify the claim that atoms, and therefore mass, are conserved during a simple chemical reaction.
    SC2015 (9-12) Chemistry
    5. Plan and conduct investigations to demonstrate different types of simple chemical reactions based on valence electron arrangements of the reactants and determine the quantity of products and reactants.
    a. Use mathematics and computational thinking to represent the ratio of reactants and products in terms of masses, molecules, and moles.
    b. Use mathematics and computational thinking to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

    Local/National Standards:

    Primary Learning Objective(s):

    The students will be able to determine limiting and excess reactants (reagents) given the amounts of two or more reactants. 

    Additional Learning Objective(s):

    Students learn critical thinking skills because they must analyze their calculations.  In typical limiting/excess reactant problems, students will do several calculations but they must be able to analyze the answers and determine what that information tells them about which reactant is limiting, which is excess, how much excess is used or how much remains, and how much product is actually formed.

     Preparation Information 

    Total Duration:

    31 to 60 Minutes

    Materials and Resources:

    S'mores Activity - manipulatives

    brown craft foam, black craft foam, white puff balls (colored paper can be substituted for the craft foam and cotton balls or white paper cut in circles for the puff balls), 3.33 " x 4" labels

    1. Cut the brown craft foam or colored paper into rectangles slightly larger than the black craft foam or colored paper (the brown rectangles will represent the graham crackers and the black rectangles will represent the chocolate bar).  You will need to cut twice as many brown rectangles as black rectangles.
    2. Cut out white paper circles or count out white puff balls to represent the marshmallows.
    3. Label the plastic baggies and follow the envelope guide for placing the appropriate number of brown rectangles, black rectangles, and white puff balls into each baggie.

    Actual S'mores (if school permits)

    graham crackers, large marshmallows, milk chocolate morsels, microwave, paper plates

    1. Once the students have completed part I of the activity and if school rules allow, students can make real S'mores.
    2. Students will build the actual S'more according to the directions on the activity sheet.  It is suggested that you use milk chocolate morsels.  The morsels heat faster and are less expensive. 
    3. Place the ingredients on a paper plate and heat for 5 - 7 second intervals until chocolate is slightly melted.  Be careful not to overheat because the graham crackers will burn. 
    4. Enjoy!

    Technology Resources Needed:

    Optional: computer, LCD projector, interactive whiteboard, document camera

    This activity can be done as a large group by building brown rectangles, black rectangles, and white circles according to one of the baggies on the envelope guide in a document or PowerPoint.  The teacher or a student can use an interactive whiteboard to move the pieces around to build the S'mores and have the class determine the limiting ingredient and the excess ingredients. A template has been provided to use as a guide.


    The teacher will need to know chemical nomenclature, balancing equations, stoichiometry, limiting and excess reactants.  The students will need to be familiar with chemical nomenclature, balancing equations, and basic stoichiometry. 

    1. Group students into diverse ability groups of two.
    2. Distribute the baggies of S'more ingredients, group cards, and activity sheets.
    3. Students will remove the S'more ingredients from the baggie and build as many S'mores as possible.  The directions are on the student activity sheet for building the S'more. 
    4. Students will complete the group card by counting the number of S'mores made, determining the ingredient that was completely consumed (limiting reactant or reagent), and counting the ingredients that remain (excess reactant or reagent).  Once the card is completed and if school rules allow, student may then make an actual S'more to enjoy.  The group card is 5 points of the activity grade.
    5. Once students have completed and turned in the group card for the S'mores activity they can return the items to the plastic baggie and continue the activity page.
    6. Part II is another real world example of hot dogs and a party.  Students will determine the limiting and excess ingredients (reactants, reagents) based on the invited guests, how many hot dogs each guest will consume, and the usual packaging for hot dogs and buns. Successfully completing this part is worth 5 points.
    7. Part III progresses the student to a real world chemical reaction.  It is important to make the connection between the balanced chemical reaction and a recipe. Successfully completeing this part is worth 5 points.

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    Assessment Strategies

    1. Groups complete the card indicating the number of S'mores they can make, which ingredient is the limiting ingredient, and which ingredients are the excess ingredients.  The completion of this task can count as 5 points of the total assignment.
    2. The student activity page will count as the remaining 10 points of the assignment - 5 points for each for part II and part III. 


    Students who complete all three parts of the activity early can use the following websites as additional practice on stoichiometry and limiting and excess reactants (reagents).

    1. Stoichiometry Tutorials and Practice
    2. Stoichiometry Video Tutorials
    3. Limiting Reactants
    4. Stoichiometry Applet


    Students who are struggling with this concept can use the following websites to review and continue practice on stoichiometry and limiting and excess reactants (reagents).

    1. Stoichiometry Review
    2. Stoichiometry Tutorials and Practice
    3. Stoichiometry Video Tutorials
    4. Limiting Reactants
    5. Stoichiometry Applet

    Each area below is a direct link to general teaching strategies/classroom accommodations for students with identified learning and/or behavior problems such as: reading or math performance below grade level; test or classroom assignments/quizzes at a failing level; failure to complete assignments independently; difficulty with short-term memory, abstract concepts, staying on task, or following directions; poor peer interaction or temper tantrums, and other learning or behavior problems.

    Presentation of Material Environment
    Time Demands Materials
    Attention Using Groups and Peers
    Assisting the Reluctant Starter Dealing with Inappropriate Behavior
    Be sure to check the student's IEP for specific accommodations.