Analysis

The analysis section describes the data and identifies and discusses trends in the data. It is very important to directly use the data to support your interpretations. It should also include an error analysis and a discussion of what may have caused any inaccuracies. Multiple error calculations should be displayed in a table. Additionally, if any calculations were used in the lab, they should be shown in this section.

Calculations: A formula should be included for each type of calculation that was used in the lab, in addition to a sample calculation. Units should be included with the sample calculations.

Analysis

2 Data is accurately summarized in written form.2 Uses empirical data to support data

interpretations and findings.2 Identifies at least one reasonable source of

error.2 Explains how sources of error could have

potentially affected data.2 Includes equations that were used for

calculations.

Analysis The rocks, in order of least to greatest density, were granite, basalt, magnetite, and hematite. Their densities were 2.2 g/mL, 3.1 g/mL, 3.5 g/mL, and 4.2 g/mL, respectively. The formula for determining the density of the rock is:

 

density = mass / (final volume – initial volume)

The following is an example calculation for the volume of the basalt rock:

 

density = 10.9g / (53.5 mL – 50 mL) = 3.1 g/mL

The absolute and percent errors for each rock (shown in Table 2) were relatively high, especially for the density of hematite and magnetite.

Table 2: The Absolute and Percent Errors of Rock Density Measurements.

The following is the equation used to determine absolute error:

absolute error = measured density – actual density

The following is an example absolute error calculation for the volume of the basalt rock:

absolute error = 3.1 g/mL – 2.9 g/mL = 0.2 = 0.2

Analysis

Rock-Type Absolute Error (g/mL) Percent Error

Hematite 1.1 21%

Basalt 0.1 6.9%

Magnetite 0.5 32%

Granite 0.6 13%

Get these by selecting the “Insert” tab, and

choosing “Symbol.” (symbol:124)

After the absolute error was found, the following equation was used to determine percent error:

percent error = (absolute error / actual density) × 100

The following is an example calculation of percent error for the basalt rock:

percent error = (0.1 g/mL / 2.9 g/mL) × 100 = 0.7 × 100 = 6.9 %

Analysis

The inaccuracies in the data may have been caused by inaccurate volume measurements. The changes in volume were small and the graduated cylinder was large, so it was difficult to make precise measurements. Additional error may have resulted from analyzing only one rock. This is because each rock sample varies slightly in its composition and the single rock that was sampled may not have been a good representation of the entire rock-type.

Analysis