A Penny for your Thoughts

Name ________________________________________
A Penny For Your Thoughts
Density is defined as the ratio of mass to volume, and its formula is found on the back of the reference table.
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The units for mass are grams (g). The units for volume are either cubic centimeters (cm ) or milliliters (mL), so the units
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for density can either be g/cm or g/mL.
Density is a physical property (describes appearance) that can be used to identify an unknown substance. It is also
important to remember that the density of an object does not depend on how much of the substance is present. For
example the density of water is 1.00 g/ml whether you have a drop, a glass, or a bucket of water.
In this lab, you will measure the mass and volume of two sets of pennies: pre-1982 pennies and 1982 and later pennies.
You will then graph the data, calculate the slope of the lines, and determine the density of the pennies.
Materials:
electronic balance
25 pre-1982 pennies PLEASE RETURN THE PENNIES!
25 1982 and older pennies
graduated cylinder
Procedure:
Each group will determine the mass and volume of their pennies and share your data with each other.
Each group will have 4 people. You will do both pre-1982 pennies and post 1982 pennies.
Group 1: 5 pennies
Group 2: 10
Group 3: 15
group 4: 20
Group 5: 25
1) Mass five pre-1982 pennies. Record this value to the hundredths place in your data table.
2) Determine the volume of the five pennies by water displacement.
3) Record your data and share it with the others in your group.
4) Repeat steps 1 – 3 for 1982 and older pennies.
Data Table:
Pre- 1982
Number of
Pennies
Mass (g)
5
10
15
20
25
Volume of
pennies (mL)
Pos-1982
Number of
Pennies
Mass (g)
5
10
15
20
25
You will do the following for each:
1. Find the density for the number of pennies your group collected both for pre-1982 and post-1982 pennies.
Note the formula is on the back of the reference table. Show your work here:
Volume of
pennies (mL)
2. According to the US Mint, pennies minted before 1982 are made of copper (density = 8.96 g/ml).
Compare your experimental density value with the accepted value by calculating your percent error for the density
(see back of reference table for formula). Show your work.
3. Graph: Make a graph of mass vs. volume for each data set. Mass should be on the y-axis, and volume should be
on the x-axis. You will plot two lines on this single graph (one line for each data set). Plot points for each set
of data. Put a small circle around each data point. Be sure to label and title your graph, and create a simple key
so we can identify each line.
Regents Questions:
1. A student determines the density of zinc to be 7.56 grams per milliliter. If the accepted density is 7.14 g/mL,
what is the student’s percent error? Show a correct numerical set up and calculate the answer.
2. An inflated airbag has a volume of 5.00 x 10 4 cm3 at STP. The density of N2(g) at STP is 0.00125 g/cm3.
What is the total number of grams of N2(g) in the airbag? Show your work!
3. Calculate the density of a 129.5-gram sample of bronze that has a volume of 14.8 cubic centimeters.
Your response must include a correct numerical setup and the calculated result.
4. The density of hydrogen at STP is 0.0899 gram per liter. Express this density to two significant figures.
______5. At STP, which physical property of aluminum always remains the same from sample to sample?
(1) mass
(2) length
(3) density
(4) volume
_____ 6. A large sample of solid calcium sulfate is crushed into smaller pieces for testing. Which two
physical properties are the same for both the large sample and one of the smaller pieces?
(1) mass and density
(2) mass and volume
(3) solubility and density
(4) solubility and volume
_____ 7. A student calculates the density of an unknown solid. The mass is 10.04 grams, and the volume
is 8.21 cubic centimeters. How many significant figures should appear in the final answer?
(1) 1
(2) 3
(3) 2
(4) 4
_____ 8. Which element has the greatest density at STP?
(1) barium
(2) magnesium (3) beryllium
(4) radium
_____ 9. Which element has the greatest density at STP?
(1) calcium
(2) chlorine
(3) carbon
(4) copper
Word Problems:
10. An unlit candle is secured to the bottom of a 200-milliliter glass beaker.
Baking soda (sodium hydrogen carbonate) is added around the base
of the candle as shown.
The candle is lit and dilute ethanoic acid is poured down the inside of the beaker. As the acid reacts with the baking soda,
bubbles of CO2 gas form. After a few seconds, the air in the beaker is replaced by 0.20 liter of CO2 gas, causing the candle
flame to go out. The density of CO2 gas is 1.8 grams per liter at room temperature.
Calculate the mass of the CO2 gas that replaced the air in the beaker. Your response must include both a correct numerical
setup and the calculated result.
11. In the late 19th century, the Hall-Herroult process was invented as an inexpensive way to produce aluminum.
In this process, Al2O3(ℓ) extracted from bauxite is dissolved in Na3AlF6 (l) in a graphite-lined tank, as shown in the
diagram below. The products are carbon dioxide and molten aluminum metal.
Compare the density of the Al(ℓ) with the density of the mixture of Al2O3 (l) and Na3AlF6 (l)