# Activity 5.3 Determining Density

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Activity 5.3 Determining Density

Activity 5.3 Determining Density Introduction How full is the bag that you take to each of your classes? Can you put any more stuff into it? What happens to the size of the bag? What happens to the mass of the bag? The size of the bag likely stayed the same, though the bag itself is probably about to burst open. When the volume of something stays the same while the mass increases, then the density increases. In this activity you will measure volume and mass to determine the density of several objects. Equipment Engineering notebook Triple beam balance or scale Graduated cylinder Dial calipers Automoblox people and wheels Wooden puzzle cube blocks Steel spheres Delrin spheres Paper clips (Optional) Aluminum ruler Density and Uses of Common Materials Chart Procedure Part I. Determining Density of a Material 1. Measure the mass or weight of the Delrin, steel, and wood samples as directed by your instructor. For improved accuracy, measure ten samples of each material and calculate the average mass or average weight. Record values including units to the appropriate precision based on the precision of the scale. Note that you need only measure either mass in SI units or weight in US units, not both. Delrin Steel Wood Mass/weight of 10 samples (include units) Mass (SI) Weight (US) Mass (SI) Weight (US) Mass (SI) Weight (US) Average mass/weight of a single sample (include units) Mass (SI) Weight (US) Mass (SI) Weight (US) Mass (SI) Weight (US) © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 1 2. Calculate the volume, mass & density of the Delrin, steel, and wood samples. For improved accuracy, measure three samples of each material and calculate the average volume. Record and calculate values to the appropriate precision including units. When adding or multiplying measurements, record the sum or product to the precision of the least precise number involved in the calculation. Delrin (diameter) Steel (diameter) Wood (wdh) Volume formula (sphere or rectangular prism, as appropriate) W D H W D H W D H Measurement #1 Measurement #2 Measurement #3 AVERAGE VOLUME: Calculate volume (Show all steps including units) AVERAGE MASS DENSITY (SI): DENSITY (US): 3. Do your results correspond to published values for the density of steel, Derlin and wood? If not, why do you think your density value(s) vary from the published values? © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 2 Part II. Determining the Plastic Materials used in Automoblox Vehicles Obtain an Automoblox vehicle from your teacher. Study the Automoblox people and the wheels. 1. Are the Automoblox people made of the same material as the Automoblox wheels? Why do you think so? How might you test your hypothesis? 2. You will determine the density of the plastic used to manufacture the Automoblox people and the Automoblox wheels. Measure the mass of the four Automoblox people and wheels. For improved accuracy, measure the four Automoblox people together and then measure the four wheels together. Record values including units to the appropriate number of significant digits. Automoblox People Automoblox Wheels Total mass/weight of all sample(s) (include units) 3. Measure the volume of the four Automoblox figures and then measure the volume of the four wheels. Because of the irregular form of each object, the volume is more easily measured using a graduated cylinder. a. Add water to the graduated cylinder until it is approximately 2/3 full. b. Record the water level. c. Carefully add samples. d. Record the new water level. Automoblox People Automoblox Wheels Water level without © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 3 samples (Include units) Water level with samples (Include units) Water volume displaced = volume of sample(s) (Show calculations) 4. Calculate the density (by hand or using Excel) of the four Automoblox figures and four wheel samples. Complete the table below or attach a print of your Excel worksheet. Be sure to include units with all measurements and quantities. Automoblox People Automoblox Wheels Total mass/weight of sample(s) Volume of sample(s) Formula for density Density (SI) Density (US) 5. Does your data support or refute you hypothesis (from number 1 above)? Explain. 6. Refer to the Common Materials Density and Uses Chart. Use your results to infer which material used in the manufacture of the Automoblox people and wheels. What other tests might further substantiate your guess? © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 4 Extend Your Learning 1. Measure the mass of the aluminum ruler and paper clip samples. Choose the appropriate number of samples of each if an average is needed for improved accuracy. Record values including units. Aluminum Ruler Paper Clips Total mass of sample(s) 2. Measure or calculate the volume of the aluminum ruler and paper clip samples. [Note that you can calculate the volume of the ruler without submerging it in water.] Show all measurements if using the indirect measurement. Sketch the object if using the calculation method. 3. Calculate the density of the aluminum ruler and paper clip samples by hand or using Excel. Complete the table below or include a print of your Excel worksheet. Be sure to use the mass and volume based on the same number of objects. Show units for all measurements and calculated quantities. Aluminum Ruler Paper Clips Mass of sample(s) Volume of sample(s) Formula for density Density (SI units) Density (US units) 4. Do your results support the manufacturer’s claim that the ruler is made of aluminum? Justify your answer. (Refer to the Common Materials Density and Uses chart.) 5. Are the paper clips made from the same material as the ruler? How do you know? © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 5 Conclusion 1. How can you use density to identify a material? 2. What are limitations of the calculated and indirect volume measurement? 3. Explain the difference between weight and mass. © 2012 Project Lead The Way, Inc. Introduction to Engineering Design Activity 5.3 Determining Density – Page 6