# Graphing the Density of Lead

## Background:

The relationship between two measurements can be shown on a graph. Density is the relationship between mass and volume. It is a measure of how much matter (mass) is packed into a certain amount of space (volume). The density of a substance doesn't change with sample size. If you have more of it (mass), it has to take up more space (volume). To calculate the density of a substance divide the mass by the volume. Typical units are: g/ml or g/cm3. Here is an example:

```                     mass of gold sample    38.6 g
Density of gold = -------------------- = ------- = 19.3 g/cm^3
volume of gold sample  2.0 cm^3
```
Sample Number Mass (g) Volume (ml)
1 5.00 0.443
2 15.0 1.33
3 24.0 2.12
4 52.0 4.60
5 64.0 5.66
6 81.0 7.17
7 95.0 8.41
8 101 8.94
9 142 12.6
10 153 13.5

## Data:

The data table to the right shows mass and volume data for ten samples of lead.

## Graphing:

Use the data to make a graph that shows the relationship between the mass (y-axis) and volume (x-axis) of the lead samples. Include an appropriate title, label and number the axes correctly. Connect the data points with a single straight line (use a ruler to draw ONE line - do not connect the dots). Position the line as close as possible to as many of the dots as possible. ## Questions:

Use your graph and the information you were given about density to answer the following questions. Where appropriate, answer in well-written, complete sentences.
1. Describe in words the equation used to determine the density of an object.

2. What is the density of sample number 3? Show your work.

3. What is the density of sample number 7? Show your work

4. Use the graph to find the volume of a lead sample with a 120 g mass.

5. For a sample of lead with a volume of 14 ml, use the graph to find its mass.

6. Describe how you can use your graph to find the volume of a sample if you only know its mass?

7. Why doesn't every data point lie exactly on the line of your graph?

8. Algebra bonus: What is the slope of the lead density line? Be sure to include the appropriate units.