Download Density of the Earth Lab procedures

Geology
Density of the earth lab
Introduction: The mass of the Earth is approximately 5.98 x 1023 kg. The scale of this measurement is difficult to
comprehend and impossible to measure directly. However, smaller scale measurements can be completed in the
laboratory that will give insight into the density and mass of Earth.
Concepts
 Measurement of mass
 Measurement of volume
 Calculating density
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Rock types
Graphing
Helpful Definitions:
Density – The concentration of matter in a material. Equals the mass divided by volume of a sample of material. D = M/V.
Lithosphere – The rigid, outermost layer of the Earth, about 100 km thick, that included the crust and part of the mantle.
Asthenosphere – A structure of the Earth found beneath the lithosphere of the Earth. It consists of more dense elements in
a partially liquid state. The structure has convection cells that transport heat energy from greater depths to more shallow
depths. Average density is 3.3 g/cm3.
Continental Crust – The upper portion of the Earth’s lithosphere that is thicker and less dense than other regions of the
lithosphere. This portion of Earth’s lithosphere tends to make up the continents. Coarse grained, felsic rocks (of granitic
nature) tend to make up most of the continental crust. Average density is 2.7 g/cm3.
Oceanic Crust – The upper portion of the Earth’s lithosphere that is thinner and more dense than other regions of the
lithosphere. This portion of Earth’s lithosphere tends to make up the ocean floor. Fine grained, mafic rocks (of basaltic
nature) tend to make up most of the oceanic crust. Average density is 3.0 g/cm3.
Igneous Rock – Rock formed from magma or lava when it cools.
Sedimentary Rock – Rock formed when sediments become pressed or cemented together.
Metamorphic Rock – Rock formed from existing rock when temperatures or pressure changes.
Activity Overview: This activity is intended to introduce indirect evidence of the composition of Earth. Direct methods
will also be used to collect composition and climate data for surface layers.
Materials
Colored pencils
Graph paper
Graduated cylinder
Balance, electronic
Three pieces of each of the
following:
Granite
Basalt
Limestone
Sandstone
Gneiss
Slate
Spheres, metal
Styrofoam ball
Procedure
Data Collection:
1. Obtain a container with three pieces of one type of sample (granite, basalt, etc.). See the Density of the Earth
Table.
2. Using a balance, find the mass of each object in the container to the nearest tenth of a gram. SAMPLES MUST
BE DRY! Record these masses in the Density of the Earth table.
3. Using a displacement cup and graduated cylinder, find the volume of each sample you have by determining
the volume of water it displaces when completely submerged. Record the volume of each sample in the Data
Table.
4. Calculate and record the density of each object in the container in the Data Table.
5. Calculate and record the average density of the three objects in the Data Table.
6. Repeat steps 1-5 for each sample type listed in the Data Table.
Creating a Line Graph of Mass vs. Volume:
1. Label the y-axis “Mass (g) – dependent variable”
2. Label the x-axis
“Volume (mL or cm3) – independent variable”
3. Determine a scale for each axis by looking at the largest number from your data. (Take the largest mass and
divide by the number of squares available on that axis…then round UP. This will be the scale for that axis. Do
the same with the largest volume.). The scale must start at zero (the origin) for both axes and the graph
should take up most of the page.
4. Plot a point on the graph representing the average mass (y-axis) and average volume in a specific color for the
first sample type from the Data Table. (You will have to calculate these from your data).
5. Draw a line from this point back to the origin, in the same color as the plotted point. The slope of this line will
represent the average density.
6. Repeat for the remaining objects on the Density Table using different colors.
7. Draw a line representing the density of water for comparison. (Hint: Water has a density of 1 g/cm3.)
8. Create an appropriate key for the graph.