Name: _________________________________ Date:_______________ Period:____
EARTH SCIENCE Density: Continental High, Ocean Low
Basalt and Granite Saul 2013
Focus Question: Which has a greater density: Basalt or Granite?
Background: The Earth is heterogeneously layered
into 3 basic parts: the crust, the mantle and the core.
Scientists believe that differences in the physical
property of density is responsible for the layering
of the Earth with the densest layers toward the
center of the Earth and the least dense layers found
at the surface of the planet. The core is believed to
be composed of iron and nickel, which are two very
dense metals. The crust is the outer most layer of
the Earth and is divided into two parts, the oceanic
crust and the continental crust. Ocean crust is made
mostly of iron-rich igneous rock known as basalt.
Continental crust is mostly composed of silica-rich
igneous rock called granite.
Image 1
Key Vocabulary: (10pts)
Crust:
Ocean Crust:
Basalt:
Continental Crust:
Granite:
Mass:
- The unit of measurement for mass is the
(g).
Volume:
- The unit of measurement for volume is the
(ml) or
cm3.)
Density:
The formula for calculating density is
The unit of measurement for density is
or
Purpose:
In this activity we will determine the experimental density of basalt and granite, the rocks that make up the ocean
crust and the continental crust.
Refer to the background information and image 1 above to help you hypothesize.
Hypothesis: (5pts) The density of the oceanic crust will be (more or less) than the density of the continental crust
because
Procedure:
1. Use the triple beam balance to find the mass (g) of each rock then record in Table 1 or 2.
2. Practice the Water Displacement Method to obtain the volume of the rock by pouring
water from the beaker into the graduated cylinder to the ______ mL line.
3. Gently tip the graduated cylinder slightly and slide the rock into the graduated cylinder
4. Record the volume of the rock + water in the data table
5. Calculate the volume of the rock only by subtracting the start volume from the volume of
the water & the rock.
6. Pour the water back into the beaker and remove the rock.
7. Find the rock’s density by dividing the Mass of Rock by the Volume of Rock.
Density Formula: D=M/V
Results (10pts):
Rock
Name
Mass (g)
Average Density of OCEAN Crust (Basalt)
Volume of
Volume of
Density of
Start Volume
Water &
rock ONLY
Rock
(ml)
Rock (ml)
(ml)
g/cm3
Average
Density
g/cm3
Basalt 1
Basalt 2
Basalt 3
Basalt 4
Basalt 5
Basalt 6
Table 1
Rock
Name
Average Density of CONTINENTAL Crust (Granite)
Volume of
Volume of
Density of
Start Volume
Mass (g)
Water &
rock ONLY
Rock
(ml)
Rock (ml)
(ml)
g/cm3
Average
Density
g/cm3
Granite 1
Granite 2
Granite 3
Granite 4
Granite 5
Granite 6
Table 2
Results
GRAPH (15 pts)
Create an appropriate graph to represents the AVERAGE density values for Granite (Continental Crust)
and Basalt (Oceanic Crust). Use the G-TAILS+S format to guide you.
Data Analysis/ Conclusion Questions:
REFER to the AVERAGE Densities to answer the questions in complete sentences.
1. (2pts) What is the experimental average density of basalt, which makes up the ocean crust?
2. (2pts) What is the experimental average density of granite, which makes up the continental
crust?
3. (15 pts) Was your hypothesis supported by the outcome of the experiment? Yes or No?
Support your response by writing about the specific experimental data values to use as the
evidence.
4. (5 pts) By carrying out experiments similar to the one you just performed, scientists have
determined the true average density of basalt (ocean crust) to be 3.0 g/cm3 and the true average
density of granite (continental crust) to be about 2.7 g/cm3.
● Examine your experimental average densities and the true density values of granite
and basalt. How are they similar and/or different?
5. (10pts) Discuss at least 2 possible sources of error that could account for any
inaccuracies or differences between the true density values and the experimental density
values.
6. (15pts) C- E- R Scientific Explanation:
Use the background information and specific
data from this investigation to explain why the
thinner ocean crust sits lower than the thicker
continental crust.
7. (5 pts) Make a prediction: How might the density values for
the mantle and the core be different from the density values of the
oceanic and continental crust? Explain your reasoning.
8. (5 pts) During this activity, each group conducted only 1 trial, but as a class we conducted 6
trials and then found an average. Explain why it is important for scientists to conduct multiple
trials in a scientific investigation?