The Density Dilemma:
The Case of the Missing Crown

A WebQuest for 8th Grade Earth Science

Designed by
Barbara A. Johnson
barbaraj@umd5.umd.edu

 gold  ? gold  ?

Introduction | Task | Process | Evaluation | Conclusion | Credits

Introduction
In this activity you will solve a dilemma by using a property of matter, density, to identify which of  5 crowns is the the one made of pure gold.

Density is a property of matter which allows us to identify the substance that makes up that matter.  The density of an object can be calculated by dividing the mass (g) of a substance by its volume (cm3).  The density of a particular kind of matter is a specific property that helps identify it.  By referring to a density chart, a person can determine the identity of a substance.

In this activity imagine that you are living in Syracuse in the Bronze Age, circa 250 BC (2,259 years ago!).  You have been summoned by the king of your land, His Majesty Hiero II, to help in a very important matter.  King Hiero has commissioned some goldsmiths to make for him a wreath crown of pure gold. Five goldsmiths brought to him five identical crowns. Hiero has hired you because he has heard rumors that only one of the five crowns is in fact pure gold! The other four might have been made of different metals! It is up to you to scientifically find which crown is the pure gold crown. Since the crown is a holy object you are not to disturb it in any way. How will you do it? Remember to choose the correct crown because the other four goldsmiths might very well lose their heads!

The Process

1Review the concept of  density at density 1 and density 2.

2.  Complete the *chart that organizes the following data about the 5 crowns in your notebook:

- all of the crowns are identical and have a volume of 180 cm3

- the 5 crowns have the following different masses

1. 1943 g,
2. 515 g,
3. 1440 g,
4. 3474 g, and
5. 2467 g.

3.  Calculate the density for each crown using the formula: Density equals mass divided by volume.  Record the density for each crown in the chart.

4.  Be certain that your chart contains complete headings for each column.  Include the unit of measurement for mass, volume, and density.

5.  Examine the chart "Density of Common Substances."

6.  Answer the *questions on the chart page to help clarify your thinking.

7. Summarize your findings in a letter persuading the king that you have correctly identified the real gold crown using scientifically accurate information. Before you begin to write, use a *graphic organizer to order your ideas in a logical way. Be certain to use supporting evidence from your density calculations and the table "Density of Common Substances."

Evaluation

Beginning

1

Developing

2

Accomplished

3

Exemplary

4

Score
Student constructs and completes chart.

1 or 2 of exemplary elements with  some understanding of the task
2 or 3 exemplary elements with a basic understanding of the task
3 out of 4 exemplary elements with a good understanding of the task
Chart has a title, labels for rows and column, correct units of measurement, and density correctly calculated.

Student provides answers to questions which clarify thinking.

Answers to questions indicate student has some understanding of the concept of density.
Answers to questions indicate student has a basic understanding of the concept of density.
Answers to questions indicate student, using analysis,  has a good understanding of the concept of density .
Answers to questions indicate student, using analysis, has a full and complete understanding of concept of density.

Student composes a  letter
using scientific information to persuade the king of the correct identification of the gold crown.

Student cites 1 or 2 elements of supporting evidence for persuasion which show some understanding of the task/problem.
Student cites 2 or 3 elements of supporting evidence for persuasion  which show a basic understanding of the task/problem.
Student,
using analysis, cites 2 or 3 elements of supporting evidence which show a good understanding of the task/problem.
Student, using analysis, has a full and complete answer which cites the definition of density, the mathematical calculations, reference to the chart "Density of common substances",  in a coherent logical presentation of  evidence to persuade.

Stated Objective or Performance

Description of identifiable performance characteristics reflecting a beginning level of performance.
Description of identifiable performance characteristics reflecting development and movement toward mastery of performance.
Description of identifiable performance characteristics reflecting mastery of performance.
Description of identifiable performance characteristics reflecting the highest level of performance.

Conclusion

By successfully completing this activity, you have learned how to use a property of matter, density, to identify matter.

Credits & References

Prentice Hall Matter:  Building Blocks of the Universe, New Jersey 1997.

Organizer for Persuasive Essay From Inspiration 6.0

www.mcs.drexel.edu~crorres/Archimedes/crown/CrownIntro.htm

cwis.nyu.edu/pages/mathmol/modules/water/density-intro.htm

Last updated on August 15, 1999. Based on a template from The WebQuest Page