## Density Discoveries

### Cheryle BorsosSanta Rosa District Schools

#### Description

Density Discoveries is a hands-on student learning opportunity for students to find the mass, volume, and density of solid matter.

#### Objectives

The student knows ways in which substances differ (for example, mass, volume, shape, density, texture, reaction to heat and light).

The student understands that mass is the amount of material in an object.

The student knows that equal volumes of different substances may have different masses.

#### Materials

- Student Lab Investigation sheets (1 per student) (See Associated File)
- One triple beam balance for each lab station (8)
- One 100mL graduated cylinder for each lab station (8)
- A water source
- Two rectangular erasers for each lab station (16)
- Three fishing lead sinkers of various sizes for each lab station (24)
- Two pieces of chalk for each lab station (16)
- One ball of art clay for each lab station (8)
- One plastic knife for each station (8)
- Class set of student calculators
- Goal 3 Standards Checklist (1 copy for teacher) (See Associated File)
- A copper penny

#### Preparations

1. Gather listed materials and set up 8 lab stations around the room.
2. Cut one of the rectangular erasers in half so that the lab stations have one whole and two half erasers.
3. Copy a class set of Student Lab Investigation sheets, and make 1 copy of the Goal 3 Standards Checklist. (See Associated File)
4. Check the triple beam balances to make sure they are functioning properly.

#### Procedures

This lesson should be taught after students have had experience finding mass on a triple beam balance, and finding volume using displacement in a graduated cylinder.

1. Gain students' attention by asking them to imagine finding a piece of gold in a streambed. Ask them to think about a way that they could determine if the gold nugget was real gold or if it was fool's gold. Allow students to share their ideas aloud.

2. After students have shared their ideas, inform them that they could use a characteristic property of matter to identify the gold. The
characteristic they could use is called density.

3. Inform students that density is a derived quantity that represents the amount of matter in a given space.

4. Ask them to recall the name of the amount of matter in a substance. (mass)

5. Then ask them to recall the name given to the amount of space an object occupies. (volume)

6. Once students have successfully identified mass and volume, demonstrate how density can be derived from knowing both quantities using the formula: D=m/v.

7. Take a moment to make sure that students understand that the unit for mass is grams and the unit for volume is cubic centimeters, thus, the unit for density is grams per cubic centimeters.

8. Provide the students with two practice examples. (If the mass of substance A is 15 grams and the volume of substance A is 5 cubic centimeters, the density of substance A is 3 grams per cubic centimeter.) (If the mass of substance B is 20 grams and the volume of substance B is 4 cubic centimeters, the density of substance B is 5 grams per cubic centimeters.)

9. Next, inform students that they will be doing an investigation to find the density of various solid substances. Invite a student to the front to model proper use of a triple beam balance to find the mass of a penny. Make sure the student calibrates the triple beam balance before taking the measurement. Record the student's result on the board. Then invite another student to the front to model using a graduated cylinder to displace water to find the volume of the penny. Make sure the student reads the meniscus of the graduated cylinder. Record the volume on the board. Ask the class to derive the density of the penny. Check for understanding and assist students still having difficulty.

10. Hand out a Student Lab Investigation sheet to each student. (See Associated File) Depending upon the level of your students, you may want to read aloud the detailed directions with your students before inviting them to move to their lab stations.

11. Once students have moved to their lab stations and have begun to perform the investigation, walk around and make sure students are working cooperatively. Also, provide feedback and assistance while students are working on the investigation. Make sure students are calibrating the triple beam balance and reading the meniscus of the graduated cylinder. This is when you will complete the Goal 3 Standards Checklist for each student. (See Associated File)

12. After students have finished the investigation, collect their lab sheets. Then bring closure to the lesson by bringing them back to the original question. How would you know if your gold nugget was real gold or fool's gold? Inform the students that gold has a density of 19.3 grams per cubic centimeter. What would the mass and volume of the nugget need to be for it to be real? Allow students some time to calculate an answer. Answers will vary. This will help confirm the lab discovery that the mass and volume of a substance can vary, but the density will remain a constant characteristic.

#### Assessments

The students complete the Student Lab Investigation sheet to identify ways in which substances differ in mass, volume, and density. They will use a data chart to conclude that density is a characteristic property of a substance. The students also construct responses to critical thinking questions. (See the Teacher Assessment Tools in the Associated File for specific answers)

#### Extensions

This lesson can be used when investigating minerals. Students can find the mass, volume, and density of various mineral samples.