1. Calculating the Average Density of Planet Earth
SES1b. Explain how the composition of the Earth’s crust, mantle and core is determined and compare it to that of other solar system objects.

2. REVIEW: DENSITY Mass per unit volume
Measurement of how tightly matter is packed together in something
D = M/V
Volume can be determined either by
linear measurement OR liquid displacement.

3. CALCULATING THE AVERAGE DENSITY EARTH
Part One:
Find volume of six mineral samples by displacement.
2. Find the mass of each using the electronic balance (grams).
Calculate the volume of each mineral using the formula for density (D=m/v).
Identify each mineral by comparing to known densities.
Safety??????

4. DATA TABLE
“Mineral Name” is the number of the sample.

5. CALCULATING THE AVERAGE DENSITY EARTH
Which is which?
The known (expected) densities of the minerals that these could be are:
Calcite – 2.71g/mL
Quartz – 2.65g/mL
Gypsum – 2.36g/mL
Fluorite – 3.13g/mL
Iron Pyrite – 5.02g/mL
Hematite – 5.26g/mL
Determine which type of mineral that each sample is according to its density and write its name in the far right column on your lab report. Draw a picture to represent each mineral.
Safety??????

6. CALCULATING THE AVERAGE DENSITY EARTH
Part Two:
Average results with known value of Iron to estimate Earth’s density. (7.87g/cc)
Calculate percent error.
Draw conclusions
Can you explain?:
Why do you think the density of each of Earth’s layers increases going toward the center?

7. HOW CLOSE ARE YOU? PERCENT OF ERROR
Percent of error is the measurement of how far off an actual value is to the approximated value. The formula used to calculate this is: It has to do with how precise a measurement is, not how “wrong” it is. Calculate the percent of error based on the “expected” value of Earth’s density. Your result is the “observed” value.
The actual average density of the Earth is 5.52 g/cm3
(its expected or “known” value).

8. LAB WRITE UP
Page One: Include the lab title, your names, and draw and label all materials you used.

9. LAB WRITE UP
Page Two: Write your procedures and the data table. Your table will include color illustrations of each specimen with data.

10. LAB WRITE UP
Page Three: Write all the formulas you need to use. Show all the work for your calculations here.

11. LAB WRITE UP
Page Three: Then draw one more table below your calculations. Write your density for each mineral in the Density column and then figure out which mineral it is:

12. LAB WRITE UP Page Three: Gypsum – 2.36g/cm3 Quartz – 2.652g/cm3
Calcite – 2.71g/cm3 Plagioclase Feldspar– 2.68g/cm3
Iron Pyrite –5.022g/cm Hematite – 5.262g/cm3

13. LAB WRITE UP Page Three:
Calculate the average density of all your mineral samples combined (add all densities, divide by 6).
Label this as the “Average density of rock”

14. LAB WRITE UP
Page Four:
Record the average density of ALL your mineral samples, from where you wrote it on page three.
Add the average density of iron (7.87 g/cm3) to the average density of YOUR samples and divide by two (2) to find a combined average. Show to calculation.
Label this as your ESTIMATED average density of the Earth.

15. LAB WRITE UP
Page Four:
PERCENT ERROR: The actual average density of the Earth is g/cm3 (its expected value). To compare the actual density of Earth to your experimental or observed value, calculate the percent of error using the formula: % Error = [(experimental – expected) / Expected] x 100
OR: % Error = [(experimental – 5.52 g/cm3) / 5.52 g/cm3] x 100
Write this formula on your paper, under your ESTIMATED/ Experimental density of Earth, plug in your estimated density and solve to find out YOUR percent error. Label the results as your percent of error.

16. LAB WRITE UP
Page Four: Write the responses to the questions.

17. LAB WRITE UP
How close are you? The group that gets the closest gets a sweet surprise! 
Which mineral had the highest density? Which had the lowest?
Why do you think different minerals have such different densities?
What layer of the earth do the rock samples represent (crust or core)? The iron?
Explain why percent of error is about variation and not about being wrong.

18. DUE DATE
Lab is due on Monday – all four pages. Come in to the media center during lunch if you need help.