Density Lesson

### Problems to Investigate:

1. Why is density a very important principle in science?
2. How can the density of different kinds of matter be measured?
3. Does size, shape, or mass and volume affect the density of a specific type of matter?

### Lesson Description:

This is a hands-on, "discovery lesson" dealing with the fundamental concept of density. Students must have acquired certain measurement skills before this lesson can be successful.

### Prerequisites:

Students should be familiar with the following:
• Names and uses of Lab Equipment
• Basic units of the Metric System.
• The Scientific Method and "Quantitative Observations".
• How to measure Mass and Volume.

### Materials:

• 5 unmarked containers of different volumes and shapes
• Balances
• Calculator
• Funnel
• Lots of Paper Towels
• Provide 3 to 4 pieces of the same substance, i.e., granite, quartz, glass, copper, etc. having different shapes and volumes, some regularly-shaped and some irregularly-shaped, 9-12 in all.
• Overflow cans

### Procedure-Part I:

1. Create Table A in your journal or print a copy of the one below.
2. Predict the volumes of each container and record their names according to volumes (most to least) in Data Table A.
3. Fill each cup with water and find the mass of each filled container to the nearest 0.l g and record.
4. Subtract the mass of the empty container from the filled container to get the mass of just the water to the nearest 0.1 g and record.
5. Find the volume of water of each filled container and record.
6. Summarize your steps so far and complete a Lab Write-up.
7. Research density.
8. Complete last column of Data Table A using the formula; density=mass/volume.
 Data Table A.-Determining Density of a Liquid Substance List by Predicted Volumes (mL) Mass of Empty Container (g) Mass of Container & Water (g) Mass of Water (g) Volume of Water (mL) Density of Water (g/mL)

### Teacher Notes:

• Through research students should have discovered that the true density of "pure" water is 1.0 g/mL.
• Students' calculations should be very close to this - .9888... or 1.0988...or something very similar. If not, need to remeasure. Students should discover that the volume and the mass need to be very close to being the same number in order to get a quotient of close to 1.0 g/mL.
• Lead students to see that when all the densities of the different volumes of water are averaged, the answer will round to 1.0 g/mL. (Providing calculations are correct as well as measurements are as close as can be.)
• Discuss with students the "hidden variables" that prohibit them from getting exactly 1.0 g/mL. For example,
• tap water instead of "pure water"
• human error
• equipment not exact
• table unlevel, etc.
• I am truly amazed at the responses that my students come up with. I always feel like I have really taught them something. Once we have gone through all of this they understand that no matter what the volume of water is, the answer will always be close to 1.0 g/mL. Thus, density is always constant if the types of matter are identical.

### Procedure-Part II:

1. Find the volume using the formula method for regularly-shaped objects. the "Water Displacement Method" for finding the volume of irregularly-shaped objects.
2. Calculate the densities of the selected pieces of matter.
3. Complete Data Table B.
4. Complete Part B of the lab writeup.
5. Graph the Results for each set of data.

 Data Table B-Determining the Densities of Solid Substances Name of Solid Mass (g) Method for Finding Volume Volume (cm3) Density (g/cm3)

### Conclusion:

1. What was the average density of the water for all the containers of water?
2. Theoretically, what is the density of pure water?
3. What are 3 factors that prevented you from getting the actual density of water?
4. What are some things that could be done next time to acquire more accurate data?
5. What are the ways that you can measure the volume of solid objects?
6. How does the method of calculating the volume of a substance affect that substance's density?
7. In your opinion, which way do you think is the most accurate? Explain.
8. In both parts, what did you discover about the density of a particular substance? Elaborate!

### Assessment:

 Scoring Rubric Lab Writeup Data Table A Data Table B Graph Questions Total 20 pts. 20 pts. 20 pts. 20 pts. 20 pts. 100 pts.
• 20 pts.- ALL Data is Complete and Accurate
• 15 pts. - MOST data is complete and accurate, however, a few mistakes were made
• 10 pts. - SOME mistakes were made, data lacks completeness and/or accuracy
• 5 pts. - MANY mistakes were made, almost totally incomplete and/or inaccurate
• 0 pts. - NO attempt was made to complete this section and/or totally inaccurate

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2/24/06

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