Density Of A Penny
Summary
In this lab, students will learn how to measure the volume and mass of an object and use that to compute density. They will then use that density to talk about experimental errors and accuracy of measurements. As they do this project, they design their own data table to show how they computed the density of a penny. They can then compare their findings to the expected results and use that to talk about the limitations of classroom equipment and small objects.
CollapseLearning Goals
Students should learn how to measure mass and volume and how to compute density. They should then be able to use these skills to predict the results of a similar experiment. They should also be able to calculate the purity of a solid metal object.
The students should learn how important it is to realize the limitations of measurements and how that relates to the relative inaccuracy of their results. This can be used to introduce or reinforce the ideas of technologies advances in the field of science.
They students should also learn the relationship between units of volume, area, and length, and how the metric system allows us to measure in both cm^3 and mL without converting.
The students should learn how important it is to realize the limitations of measurements and how that relates to the relative inaccuracy of their results. This can be used to introduce or reinforce the ideas of technologies advances in the field of science.
They students should also learn the relationship between units of volume, area, and length, and how the metric system allows us to measure in both cm^3 and mL without converting.
Context for Use
Lab Project- 1/2 day intro (after lecturing on density)
1 hr completion-
1/2 day reflection and application
1 hr completion-
1/2 day reflection and application
Description and Teaching Materials
This lesson is used to reinforce the teachings of density and the application to metals. This is also a good time to tell the story of Archimedes.
After the main concepts of density have been taught, refer them to a table of the densities of copper and the densities of zinc. Ask them how they could measure density in a coin?
1. Use a balance to get the mass (show them the correct way to use a balance).
2. How to get the volume. Why is a ruler a poor choice to measure the volume (to small). Introduce the idea of displacement. If they put a penny (or multiple pennies to make a bigger change) in a graduated cylinder, the change in water volume is the volume of the penny. (Show them how to use the graduated cylinder correctly.)
Have them do an experiment where they measure the density of one penny multiple times and the average density of 5 pennies multiple times. They should do this with both copper pennies and zinc pennies and write the results in a self-designed data table.
Have the class record all the results and talk about why there may be differences in the results (error in measurements). Use this to reinforce the concept of multiple trials.
Ask them what could make their results more accurate. (More accurate tools)
Then compare the calculate density to the actual density of the metals and reward the closest group.
Then calculate the actual density based on the actual makeup of the pennies. (95% copper, 97.5% zinc)
Then have the students test other items in the class (rings, necklaces) to see how close to pure they are.
After the main concepts of density have been taught, refer them to a table of the densities of copper and the densities of zinc. Ask them how they could measure density in a coin?
1. Use a balance to get the mass (show them the correct way to use a balance).
2. How to get the volume. Why is a ruler a poor choice to measure the volume (to small). Introduce the idea of displacement. If they put a penny (or multiple pennies to make a bigger change) in a graduated cylinder, the change in water volume is the volume of the penny. (Show them how to use the graduated cylinder correctly.)
Have them do an experiment where they measure the density of one penny multiple times and the average density of 5 pennies multiple times. They should do this with both copper pennies and zinc pennies and write the results in a self-designed data table.
Have the class record all the results and talk about why there may be differences in the results (error in measurements). Use this to reinforce the concept of multiple trials.
Ask them what could make their results more accurate. (More accurate tools)
Then compare the calculate density to the actual density of the metals and reward the closest group.
Then calculate the actual density based on the actual makeup of the pennies. (95% copper, 97.5% zinc)
Then have the students test other items in the class (rings, necklaces) to see how close to pure they are.
Teaching Notes and Tips
This lab can also be developed as an inquiry lab
Be careful dropping metal into a glass cylinder.
Don't put your wedding ring into a cylinder where it might get stuck.
Be sure to keep the zinc and copper pennies separate.
Really emphasize how they all did not get the right answer, rather, that the range of answers is what we were looking at.
Be careful dropping metal into a glass cylinder.
Don't put your wedding ring into a cylinder where it might get stuck.
Be sure to keep the zinc and copper pennies separate.
Really emphasize how they all did not get the right answer, rather, that the range of answers is what we were looking at.
Assessment
Assess the quality of the data tables and include questions about the lab on a later test. During the lab, identify the groups having trouble and orally quiz as many students as possible.
You can also have an item of a known density and see what group gets the closest.
You can also have an item of a known density and see what group gets the closest.
Standards
8.I.B.2- use of multiple samples
8.I.B.3- Technology and math
9.I.B.4- Errors
6.II.A.5- Mass, Vol, Density
8.I.B.3- Technology and math
9.I.B.4- Errors
6.II.A.5- Mass, Vol, Density