**Densities
of Liquids, Significant Figures, and Graph Interpretation
**

**Objective: **Properly use Sig.
Figs. in density calculations, and plot a graph of the data.

**Materials**: alcohol,
water, ethylene glycol, graduated cylinders, balance

**Note: Use of Sig. Figs. in measurements and
calculations is required. **

**Methods**

1. Mass a 50.0 mL or 100 mL
graduated cylinder.

2. Add approximately 10 mL of
liquid A, then determine the mass of the liquid by subtracting the cylinder’s
mass.

[*Note: volumes can vary, but must be known exactly to 0.1 mL*]

3. Add 10 mL more of the same
liquid; mass again. Repeat up to a total
of 50 mL or slightly less.

4. Clean your graduated cylinder,
then dry it.

5. Repeat Steps 1 - 4 for the two
other liquids.

6. Determine the mass and the
area of the aluminum foil sheet at your lab station.

**Analysis**

1. Plot the mass (y axis) vs.
volume (x axis) for all liquids. Draw a
best fit straight line for each.

2. Calculate the density of each
liquid using the liquid's* total mass at the maximum volume*.

3. Calculate the slope of each
line. What does the slope represent and
what are the units?

4. Estimate by *interpolation*
the mass of each liquid at 16.0 mL, 27.0 mL, and 44.0 mL. Write an equation for the graph of the line.
(Hint: y = mx + b)

5. Which measurement was limiting
in accuracy, mass or volume. Explain.

6. Define the term *interpolation*. Can you justify *extrapolation* on this
graph? Explain.

7. Why can the water measurements
be used as an indicator of your accuracy and precision?

8. The density of aluminum is 2.7
g/cm^{3}. Determine the
thickness of the aluminum foil sheet on your lab table.

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