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### Summary

In this activity, students will solve problems individually on a series of sheets shared between students. I use density conversions as an introductory topic for this activity because the concept is fairly simple for students. I want the students to learn the process first. When students have an understanding of the method, I give them more challenging problems to solve in this format. I have included example Round Robin sheets for density calculations.

### Grade Level

High school

### Objectives

By the end of this lesson, students should be able to

- Solve given density problems in a timely manner.
- Check the work of peers and be able to identify and fix errors.

### Chemistry Topics

This lesson supports students’ understanding of

- Density calculations

### Time

**Teacher Preparation**: 5-30 minutes

**Lesson**: 20-25 minutes

### Materials

- Round Robin sheets (I usually make them in sets of 4)
- Timer (I use www.timeanddate.com/stopwatch for their interval timer, but any timer will do)
- Calculators

### Safety

- No safety considerations are needed for this activity.

### Teacher Notes

- This activity is not suited to introducing material but works very well as a review.
- Prior to starting, make sure your students have what they need to do the math (phone, calculator, scratch pad—whatever you deem appropriate!)
- I change the time I give students, as needed, because the first problem always takes longer than the other 3 problems will.
- I incorporate a few seconds for the passing of the papers.
- I make the same problem type for each problem number, regardless of the sheet—for example, problem 1 will be a “Solve-for-density” problem on each of the four versions, while problem 2 will be a “Solve-for-volume” problem, so that afterwards I can talk in general about how to solve each problem type and I am not leaving students out of the discussion.

### For the Student

### Lesson

Round Robin Sheet 1

**Directions: **You will have about 3 minutes to do the problem in your section. At the signal pass your paper to the left, check the problem done before you, then write your initials in the blank and do the next problem.

As a group of 4, you will solve the problems on this sheet. Underline the Q. Circle the variables. SHOW ALL MATH WORK!

Problem 1: Solver initials _____**
Use D=m/V to solve**: A brick has a mass of 4kg. It occupies 0.8 L of space. What is it the density of the brick?

Problem 2: Solver initials _____**
Use D=m/V to solve**: What volume does a 20g aluminum block occupy (D

_{Al}= 2.70g/mL)?

Problem 3: Solver initials _____**
Use D=m/V to solve**: Iron has a density of 7.87 g/mL. What mass of iron occupies a volume of 20mL?

Problem 4: Solver initials _____**
Use D=m/V to solve: ** A tin can has a density of 7.28g/mL and a volume of 300.1 mL. What is the mass of the tin can?

**Round Robin Sheet 2**

**Directions:** You will have about 3 minutes to do the problem in your section. At the signal pass your paper to the left, check the problem done before you, then write your initials in the blank and do the next problem.

As a group of 4, you will solve the problems on this sheet. Underline the Q. Circle the variables. SHOW ALL MATH WORK!

Problem 1: Solver initials _____**
Use D=m/V to solve**: A brick has a mass of 3kg. It occupies 0.75 L of space. What is it the density of the brick?

Problem 2: Solver initials _____**
Use D=m/V to solve**: What volume does a 60g aluminum block occupy (D

_{Al}= 2.70g/mL)?

Problem 3: Solver initials _____**
Use D=m/V to solve**: Iron has a density of 7.87 g/mL. What mass of iron occupies a volume of 50mL?

Problem 4: Solver initials _____**
Use D=m/V to solve:** A tin can has a density of 7.28g/mL and a volume of 250 mL. What is the mass of the tin can?

**Round Robin Sheet 3**

**Directions:** You will have about 3 minutes to do the problem in your section. At the signal pass your paper to the left, check the problem done before you, then write your initials in the blank and do the next problem.

As a group of 4, you will solve the problems on this sheet. Underline the Q. Circle the variables. SHOW ALL MATH WORK!

Problem 1: Solver initials _____**
Use D=m/V to solve**: A brick has a mass of 5kg. It occupies 1.1 L of space. What is it the density of the brick?

Problem 2: Solver initials _____

**Use D=m/V to solve**: What volume does a 25g aluminum block occupy (D_{Al} = 2.70g/mL)?

Problem 3: Solver initials _____**
Use D=m/V to solve**: Iron has a density of 7.87 g/mL. What mass of iron occupies a volume of 300mL?

Problem 4: Solver initials ______**
Use D=m/V to solve: ** A tin can has a density of 7.28g/mL and a volume of 500 mL. What is the mass of the tin can?

**Round Robin Sheet 4**

**Directions:** You will have about 3 minutes to do the problem in your section. At the signal pass your paper to the left, check the problem done before you, then write your initials in the blank and do the next problem.

Problem 1: Solver initials _____**
Use D=m/V to solve**: A brick has a mass of 2kg. It occupies 0.5 L of space. What is it the density of the brick?

Problem 2: Solver initials _____**
Use D=m/V to solve**: What volume does a 10g aluminum block occupy (D

_{Al}= 2.70g/mL)

Problem 3: Solver initials _____**
Use D=m/V to solve**: Iron has a density of 7.87 g/mL. What mass of iron occupies a volume of 450mL?

Problem 4: Solver initials _____**
Use D=m/V to solve:** A tin can has a density of 7.28g/mL and a volume of 50 mL. What is the mass of the tin can?