### Summary

This is part 2 of a 3-part lesson. In this lesson, students will reflect on the purpose and significance of stoichiometry in understanding the quantitative aspects of a chemical reaction. This lesson encourages students to think about how stoichiometry calculations can provide insights into the relative amounts of reactants consumed and products formed, as well as the stoichiometric ratios between them. Additionally, it encourages students to consider how stoichiometry can be applied to real-world scenarios, such as determining the number of reactants needed for a desired outcome. Before this lesson, students should be able to read a periodic table in order to calculate the molecular/molar weight of an element/compound. Students should also know how to balance equations and know how to calculate mole to mole ratios before completing this lesson.

### Essential Question(s)

How can stoichiometry calculations help us understand the relationship between reactants and products in a chemical reaction?

### Snapshot

**Engage**

Students use the I Notice, I Wonder strategy to formulate what’s needed to create a bouncy ball.

**Explore**

Students make predictions and develop their own bouncy balls.

**Explain**

Students watch a video on how to do gram to gram conversions in stoichiometry.

**Extend**

Students apply and demonstrate their understanding of how to convert grams to grams.

**Evaluate**

Students explain their understanding of gram-to-gram conversion using the My Favorite Mistake strategy.

### Materials

Lesson Slides (attached)

I Notice, I Wonder handout (attached; one per student)

Bouncy Ball Instructions handout (attached; one per student)

Stoichiometry: Grams to Grams Notes (attached; one per student)

Stoichiometry Race Handout (attached; one per student)

Question Slips handout (attached; one per group)

My Favorite Mistake Handout (attached; one per student)

Stoichiometry: Grams to Grams Notes (Teacher’s Copy) (attached; optional)

Stoichiometry Race Steps handout (attached; recommend to print in color and laminate; 3-4 copies)

1 tablespoon of borax [found in the laundry section of the grocery store] (one per student)

1/2 cup or warm water (one per student)

1 bottle of glue (one per group)

1 tablespoon of cornstarch (one per student)

Measuring teaspoon/tablespoon set (1/4 tsp, 1/2 tsp, 1 tsp, & 1 tbsp)

Box of food coloring (one-two per class; optional)

Meter Stick (one per group)

iPad/Phone camera (one per group)

Whiteboard (one per student)

Dry erase markers (one per student)

Craft Sticks (one per group)

Bowls (two per group)

Masking tape (one per group of students)

Calculator (one per group/student; optional)

Periodic table (one per group)

Green, Red, and Yellow cups (one set per group)

### Engage

5 Minute(s)

This is part 2 of a three-part series. Consider teaching Part 1, Balancing Act 1: Stoichiometry—Moles to Moles.

Use the attached **Lesson Slides** to follow along with the lesson. Begin with **slide 3. **Briefly read aloud the essential question:* How can stoichiometry calculations help us understand the relationship between reactants and products in a chemical reaction? *Next, move to **slide 4 **and share the objectives with your students to the extent you feel necessary.

Display **slide 5** and Introduce students to the I Notice, I Wonder** **instructional strategy and how it can help them observe and reflect on their experiences. Remind them that observations* *are factual statements about what they see, while wonders* *are questions or curiosities they have about the phenomena they observe. Explain to the students that they will be using the I Notice, I Wonder strategy to observe and reflect on the ball. Gather the students in a comfortable viewing area where they can all easily see the ball in motion.

Bounce the ball in front of the students and ask them to observe the ball silently. Pass around a ball or two for students to closely examine. You may encourage them to pay attention to consider its feel, height, speed, chemical makeup, and any other relevant details they notice about the ball. Remind them to record any observation and questions that come to mind.

After bouncing the ball, facilitate a class discussion based on the "I Notice, I Wonder" statements. Encourage students to share their observations and questions. Guide the discussion to explore possible explanations for their wonders and to deepen their understanding of what the ball was made of that contributed to its ability to bounce.

### Explore

40 Minute(s)

Display **slide 6**. Organize students into groups of 3-4 and pass out the **Bouncy Ball Instructions **handout. Give students time to collect materials. Inform students that they are going to make their own bouncy ball but the glue amount will be missing. Have students collect all the supplies they need.

Have students follow the directions on the handout. Once students have shaped their bouncy ball, have each group member drop it from the same height (top of meter stick) onto a hard surface, the floor, to test its bounce.

Have students test and record their bounce from the bottom of the ball. Have the group compare scores and the student with the highest score is the winner. Have the winner from their group test their ball against the winners of the other group(s). Have students continue to compete until you have one winner. Have the winner share out the amount of glue they used. Students only need to record the top four highest bounces on the Round 2 Whole Class chart in the Bouncy Ball Instructions handout. Afterwards, direct students to complete the analysis questions individually or as a group.

Display **slide** **7** and discuss with the class how the borax and glue react together. Inform students that the correct amount of glue is 6 teaspoon or 2 tablespoons.

### Explain

20 Minute(s)

Display **slide 8** and pass out the **Stoichiometry: Grams to Grams Notes **handout. Review what stoichiometry is with the class.

Display **slide 13** and go over the steps needed to solve a stoichiometry problem from grams to grams.

Display **slide 14** and review the setup for grams-to-grams conversions. This slide is animated to review each step in the table.

Display **slide 15** and inform the students they will complete a problem while watching the video. Show ketzbook’s Stoichiometry Tricks video and have students work through the problem with the video. Ensure that the video is easily accessible and can be viewed without any issues. After watching the video, allocate time for reflection and discussion of misconceptions.

Display **slide 17** to review an example problem as a whole class for the next activity. Using a 2x4 table that you’ve created on the floor in the front of the classroom (either in advance or now), choose seven volunteers to come up to the front of the room and hand each a dry erase board and marker. Each student will represent a specific element or compound and units in the chemical equation. Display **slides 18 - 25** as you complete each step. On their whiteboards, have students write what they represent in the problem and then stand in the corresponding place in the table. While walking through the problem as a class, have the students complete the problem on their handout.

The sample problem: If 14 grams of H_{2} and excess O_{2} react to produce water, how many grams of H_{2}O are produced?

First, students must balance out the equation.

___H_{2} +____ O_{2 }->___ H_{2}O

Answer: 2 H_{2} + 1 O_{2 }-> 2 H_{2}O

Slide 18: One student writes "14 g H_{2}" (provided from the problem) and stands in the first space of the table.

Slide 19: The student for the next step writes "2.02 g H_{2}" (molar mass of hydrogen) on their board and steps into the next space of the table. Continue the process with slides 20-25.

As students work through the reaction and cancel out with another student's element or compound with units, they sit down to indicate that they have completed their part in the reaction. For example, in the problem mentioned above, since they both are “g H_{2}“, they cancel each other out and both take a seat. Once seated, they cross out the units g H_{2} but not the numbers on their white board. Then the next person will be “1 mol H_{2} “ step into the next space. The group continues working together until all students have canceled out, are seated, and have reached grams of H_{2}O. At the final step, students solve across the table to determine the mass of H_{2}O produced, focusing on just the numbers and units they have left in their equation set up.

### Extend

40 Minute(s)

Display **slide 26. **Inform students it is now their turn to work in groups using tables around the room that they can create now or that you could have premade beforehand. They will race other groups to solve all three problems correctly. Divide students into groups of five-seven (or no more than eight) and ensure each student has a whiteboard and a marker to perform calculations and keep track of their progress. Provide each student with the attached **Stoichiometry Race Grams- to-Grams **handout. Then assign a 2x4 table to each group.

Display **slide 27** and go over the directions for the race. Instruct students to assign themselves a position. Once they have solved the problem, they should check their work as a team to ensure accuracy. When they are confident in their answer, they can change their cup color to green to be checked by the teacher. Once they have completed question 1 correctly and have it recorded on their handout, give them question 2. Repeat with question 3.

The first group to complete all three problems correctly wins.

Display **slide 28** and go over what each color of cup represents**. **Inform students that as they are working that they will use the cups to display the following:

Green - We are done.

Yellow - We are working.

Red - We need assistance.

Everyone should start with a yellow cup on the top of their stack. Provide each group with a stack of green, yellow, and red cups, calculator, and periodic table. Pass out question 1 from the **Question Slips** handout; have students keep it face down until the race begins. Once students are ready, give the signal for the race to begin.

### Evaluate

10 Minute(s)

Display **slide 29. **Remind the students about the My Favorite Mistake strategy and how it can help them improve their problem-solving skills. Have each group reflect on the three problems from the Stoichiometry Race on the back of their Stoichiometry Race handout. In their groups, give them 2 minutes to identify one area where they repeatedly made mistakes and had to go back and correct. Have them discuss the following prompts:

What mistake did your group make?

Why did you guys make it?

What can you do differently in the future to keep from making that mistake?

Have each group share with the class.

Next, consider teaching Balancing Act, Part 3: Stoichiometry—Percent Yields.

### Resources

Foundation, C.-12. (n.d.). 12 foundation. CK. https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/12.1/primary/lesson/everyday-stoichiometry-chem/

Foundation, C.-12. (n.d.-a). 12 foundation. CK. https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/10.4/primary/lesson/conversions-between-moles-and-mass-chem/

Foundation, C.-12. (n.d.-a). 12 foundation. CK. https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/10.2/primary/lesson/conversions-between-moles-and-atoms-chem/

K20 Center. (n.d.). I Notice, I Wonder. Strategies. https://learn.k20center.ou.edu/strategy/180

K20 Center. (n.d.). My Favorite Mistake. Strategies. https://learn.k20center.ou.edu/strategy/115

Malia. (2022a, April 20).

*How to make bouncy balls*. The stem laboratory. https://thestemlaboratory.com/how-to-make-bouncy-balls/YouTube. (2017a, March 26).

*Stoichiometry tricks*. Video. YouTube. https://www.youtube.com/watch?v=-1xfnq8yGk8