Density Of Earth

Density Of Earth
In this lab, we will attempt to determine the density of the Earth. Dr. Henry Cavendish is one of the first scientists that calculated the mass and density of the Earth. He accomplished this by assembling a suspended metal rod with two lead spheres hanging freely. Cavendish then placed masses of metal near the spheres in order to measure the force of attraction between them. Based on this experiment, he was able to determine the attraction of a mass the size of the Earth and hence determine the Earth’s density. This experiment has become known as the Cavendish Experiment.
Materials: triple beam balance, graduated cylinder, water, calculator, basalt, granite, slate
Procedure:

1. 
   Record the mass of the three rock samples.
   
2. 
   Use water displacement method (write procedure below) and record the volume of all rock samples provided.
   
3. 
   Calculate the density of each rock type. Round to 2 decimal places.
   

Observations:

Sample	Mass	Volume	Density
Granite
Slate
Basalt
Iron	X	X	7.87 g/cm^3

Conclusion Questions:

1. 
   Calculate the average density of the 3 rocks, Granite, Slate and Basalt.
   

(Density of Granite + Density of Slate + Density of Basalt) / 3

2. 
   Write a statement about the density of iron to the average density you calculated in question one.
   

3. 
   Add the density of iron to the average density (calculated in question 1) and divide by two. This number represents the density of the Earth.
   

(Density calculated from Question #1 + Density of Iron) / 2

4. 
   Calculate the percent error between your answers to #3 and #4. The accepted value is ____________
   

5. 
   What layer of the Earth does the iron sample represent?