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ACTIVITY in Balancing Equations, Stoichiometry, Limiting Reactant, Mole Concept, Dimensional Analysis, Molar Mass. Last updated November 10, 2021.
Summary
In this activity, students will use candy to investigate stoichiometry and mole-gram relationships in chemical equations. It could also be used to introduce the concept of limiting reactants.
Grade Level
High school
NGSS Alignment
This activity will help prepare your students to meet the following scientific and engineering practices:
- Scientific and Engineering Practices:
- Using Mathematics and Computational Thinking
- Developing and Using Models
Objectives
By the end of this activity, students should be able to:
- Write balanced equations given the formulas of reactants and products.
- Perform stoichiometric calculations (mole-to-mole and gram-to-mole) using balanced equations.
Chemistry Topics
This activity supports students’ understanding of
- Balanced equations
- Molar mass
- Stoichiometry
- Dimensional analysis
Time
Teacher Preparation: 15-20 minutes
Lesson: 50 minutes
Materials
For each group:
- Balance
- Bag with the following food items (at least):
- Butterscotch pieces (2)
- Peppermints (1)
- Animal crackers (6)
- Smarties (4)
- Skittles (2)
- Starbursts (2)
- M&Ms (10)
- Jelly beans (30)
- Student handout
Safety
- Do not consume lab materials, even if they’re otherwise edible products.
- Food in the lab should be considered a chemical not for consumption.
Teacher Notes
- Students should have been exposed to chemical symbols/formulas (including polyatomic elements), balanced equations, and dimensional analysis prior to completing this activity.
- A plastic bag of candy items should be prepared ahead of time. Suggested quantities are listed in the materials section. The quantities listed are enough candy for no excess chemical in each reaction and match the exact ratios of the coefficients of each balanced equation. If you want to add in a limiting reactant component to this activity, you can add additional pieces of candy to the bag so that there are extras of some “elements,” representing excess reagents.
- Each piece of candy represents one mole of that “element”.
- When asked how many moles of polyatomic elements (ex: S_{4}, Sk_{2}, Mm_{5}, Jb_{2}) are used, it is referring to how many moles of the molecule/unit, not the individual atoms. Just like if you were to use the equation 2 H_{2} + O_{2} → 2 H_{2}O and you asked “How many moles of hydrogen were used in this reaction?” the ideal answer would be 2 moles of hydrogen (H_{2}) since elemental hydrogen is understood to be diatomic, even though four moles of hydrogen atoms were used. Be sure this is clear to students as they work on those problems. Alternatively, you could rewrite the questions using the formula rather than the name (“St_{4}” rather than “smarties”), but it is good for them to learn the distinction.
- Molar masses are determined by finding the mass of one unit of candy formula (ex: Bs → molar mass = mass of 1 butterscotch piece; S_{4} → molar mass = mass of 4 smarties).
- There is nothing sacred about the types of candies used in this activity – you can always sub out a different type of candy if you can’t find one. Or make it seasonal – candy hearts for Valentine’s Day, candy corn for Halloween, candy canes for Christmas, etc.
- If you want to have candy available for students to eat after the lab (but not in the lab!), have a separate stash of candy that hasn’t come into contact with the balance.
For the Student
Lesson
Complete the following table using the candy provided. Do not unwrap or eat any candy. Complete the missing information in the table.
Element/Compound | Symbol | Molar Mass (g/mol) |
Butterscotch | Bs | |
Peppermint | Pe | |
Pepperscotch | Bs_{2}Pe | |
Animal Cracker | An | |
Smarties | St_{4} | |
Animartie | An_{3}St_{2} | |
Skittles | Sk_{2} | |
Starburst | Su | |
Skittleburst | Sk_{2}Su_{2} | |
M&M’s | Mm_{5} | |
Jelly beans | Jb_{2} | |
Mmelly | MmJb_{3} |
Use the candy in the bag to illustrate each reaction and answer the questions.
- Butterscotch reacts with peppermint to form pepperscotch.
- Write the balanced equation.
- How many moles of pepperscotch can be formed by the elements in the bag?
- How many moles of butterscotch were used?
- How many moles of peppermint were used?
- If 18 moles of pepperscotch were produced, how many moles of butterscotch and how many moles of peppermint were used in the reaction?
- How many moles of pepperscotch can be made with 48.0 g of peppermints?
- How many grams of pepperscotch can be produced if you start with 50.0 g of butterscotch?
- Animal cracker reacts with smarties to form animartie.
- Write the balanced equation.
- How many moles of animarties can be formed by the elements in the bag?
- How many moles of animal cracker were used?
- How many moles of smarties were used?
- How many moles of animarties can be made from 12.75 mols of animal crackers?
- How many grams of animarties can be made from 31.90 mols of smarties?
- Starbursts react with skittles to from a skittleburst.
- Write the balanced equation.
- How many moles of skittlebursts can be formed by the elements in the bag?
- How many moles of starburst were used?
- How many moles of skittles were used?
- How many moles of skittles are needed to make 23.3 mols of skittlebursts?
- How many grams of skittlebursts can be made from 42.65 g of starburst?
- M&M’s reacts with jelly beans to form a mmelly.
- Write the balanced equation.
- How many moles of mmelly can be formed by the elements in the bag?
- How many moles of M&M’s were used?
- How many moles of jelly beans were used?
- How many moles of mmelly can be made with 60.0 g of jelly beans?
- How many moles of M&M’s are required to make 35 mols of mmelly?