Objectives:

- The learner will accurately use a balance to measure the mass of an object.
- The learner will accurately measure volume using both length x width x height and water-displacement.
- The learner will calculate the density of an object using quantitative measurements made in lab and the density formula.

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*Lesson submitted by Troy Schuknecht*

What You Need:
*Every lab group will need:*
- 25 mL graduated cylinder
- Ruler
- 4 specific gravity cylinders made of different types of metal. (or any metal objects will do)
- 3 rectangular blocks of wood made of different types of wood.
- A small cork
- 10 pennies (pre-1982)
- 10 pennies (post-1982)
- Water
- Oil
- Triple Beam Pro Balance (I use Ohaus balances in my classroom)

Preparation Instructions:
- Students should be trained on the use of the density formula, water-displacement method, and triple-beam balance techniques.
- Explain to students that they will need to trouble-shoot in order to figure out how to measure some of these items.

What to Do:

Step 1: Help students generate a data table with the following columns
- Object
- Mass
- Volume
- Density

Step 2: Have students measure the mass and volume of objects in the following order, so that the more challenging objects come last.

I have provided hints for the teacher on how to measure some of the objects, only share these with students after they have attempted to problem solve on their own.

**Specific gravity cylinders**
- For volume, use water-displacement. They should all have the same volume.
- This should be helpful to teach students more about density because they will see that if the volume remains the same, mass and density are directly proportional.

**Blocks of wood**

- For volume, use the formula length x width x height.

**Pennies**

- For both volume and mass measurements, measure all 10 using your balance and then divide by 10 to find a more accurate measurement for one single penny.
- Pre-1982, pennies were mostly copper. Then with the electronics boom, copper became quite expensive and pennies began being made mostly of zinc and are only copper plated.

**Cork**
- Since cork floats, it creates a unique challenge for the volume measurement. The student needs to place a known volume object on top of the cork to get it to sink for water-displacement.

**Liquids**

- When massing a liquid, one cannot merely pour the liquid onto the balance. It is important for students to realize this and know how to either zero the balance with the empty container on top or subtract the mass of the empty container from the mass measurement.

Step 3: Ask students to use their mass and volume measurements to calculate density.

Step 4: In the end, hold a discussion about the different types of objects and their densities.
- Special focus should be given to the specific gravity cylinders as this is quite instructive on the relationship between mass and density.
- Additionally, pour the oil on top of the water and ask students to hypothesize about the separation they witness.

Wrapping Up:

I really like this lesson because it forces students to think critically and creatively about object density and to solve problems to figure out different strategies and methods for calculating mass measurements.

Additional Resources:
**Other Mass Measurement Lessons:**
Measurement products that I use in my classroom lab:

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