Teaching Density in the Physics/Chemistry Lab, Step 5

by John R. Walkup, Ph.D.

DOK-1/DOK-2

Throughout the lesson, the instructor will call on students to answer the following questions:

1. Describe a ratio in your own words.
2. What is the definition of density?
3. Describe density in your own words.
4. What is the definition of mass?
5. Describe mass in your own words. How would describe the difference between mass and weight to a friend?
6. What is the relationship between density and mass? Between density and volume?
7. What does the density ratio 4 g/cm3 mean in terms of unit volume?
8. Describe why 4 g/50 cm3 is the same as 4/50 g/cm3.
9. What does the ratio 50 cm3/4 g mean in terms of unit mass?
10. Suppose someone wants a color that comes from mixing 3 parts of blue with 2 parts yellow. Describe how you would use ratios to determine how much paint to sell this person if they need a total of 15 gallons of paint.
11. A density ratio is 2 gm/cm3. Use your model to determine how much mass there will be in 3 cm3 of this material.
12. A density ratio is 2 gm/cm3. Use your model to determine how much volume is needed to hold 8 grams of this material.
13. What is the most important thing you learned in this lab?
14. Can you identify other materials that will have a similar density to Silly Putty?
15. Can you identify other materials that will have a greater/lesser density than Silly Putty?
16. Is Styrofoam expected to have a lesser density than Silly Putty? Explain.
17. Which will weigh more: A pound of feathers or a pound of gold? What does this tell us about the importance of density?
18. Why is it important that Silly Putty is not easily compressable?
19. What would compressing a substance do to its density? Why?

DOK-3/DOK-4

Working as a team, students will answer the following questions:

1. What could be done to minimize the variability in our measurements?
2. How would you evaluate another company’s claims about the density of its product?
3. How do you think ratios could be used in business? Construction? Art? Health? Sports?  
4. Not all of your measurements of Silly Putty come out the same. Explain why.
5. Looking at your data, can you conclude that your measurements of density show that the density of Silly Putty is a specific property of Silly Putty?
6. How would you modify this experiment to measure the density of a liquid, like water? Describe the problems you will encounter.
7. Can you describe air and other gases using density? Explore this topic on the Internet.
8. How would you modify this experiment to measure the density of a gas, like air? Describe the problems you will encounter.
9. Without performing any Internet searches, what other uses of density can you identify?
10. What problems would you encounter if we tried to use an Almond Joy candy bar in this experiment instead of Silly Putty?  What does this say about the density of materials?

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