Background: Density is an intensive physical property, a constant relationship between the mass and volume of a specific type of matter. Measurements for both mass and volume can be obtained for a sample of metal. The relationship between mass and volume can be shown graphically by plotting the volume of a metal sample on the horizontal x-axis and the mass of the metal sample along the vertical y-axis. Plotting the values for samples of increasing size, a linear relationship can be seen for density (slope = density).
PRE-LAB QUESTIONS: (Please answer the pre-lab questions in your composition notebook)
1) What is the volume of the water in 2) What is the volume of the metal shot & the the graduated cylinder shown below? water shown in the graduated cylinder below?
WATER ONLY WATER & METAL SHOT
3) What is the volume of the metal shot that was added to the graduated cylinder?
4) Read over the procedure for tomorrow’s lab. Record a list of materials that will be used. In addition, create a clearly labeled data table for the measurements you will need to record. ABSOLUTELY NO METAL SHOT CAN BE PUT IN THE SINKS!!! FOR CLEAN UP--PLACE ALL METAL WHERE INSTRUCTED. ALL SHOT GOES
INTO THE RINSE BINS TO BE HEATED AND REUSED. SERIOUS POINTS WILL BE DEDUCTED FOM FINAL LAB GRADE IF YOU BREAK THIS RULE!! MATERIALS: For your lab report, list only the materials that you use in the lab today
PROCEDURE:
1. Obtain a clean, empty 10 mL graduated cylinder and add approximately 4 mL of water. Record the exact volume. (=Vinitial ) ***(Consider significant figures when measuring! Remember to estimate the last digit)** 2. Using a small plastic spoon, measure out one SMALL scoop of metal shot. Transfer the metal shot to a weigh boat. Measure and record the mass of the metal shot (=M1). 3. Add the scoop of metal to the graduated cylinder. 4. Record the new volume (=Vfinal) 5. Determine the volume of the metal added using water displacement. (Vfinal – Vinitial) 6. Record the volume of the metal 7. Measure and record the mass of another SMALL scoop of metal shot (=M2), then add it to the graduated cylinder. (Note: The total metal mass must include the amount of metal that was already in the graduated cylinder plus what was just added. So your current metal mass is now M1 + M2) 8. Determine the total volume of the metal by water displacement. 9. Record the volume of the metal 10. Continue to repeat steps 4-9 until at least five scoops of metal shot have been added. (You should then have at least five data points for your graph)
GRAPH RESULTS: (using Excel in the computer lab on Thursday)- Bring your flashdrives to save your work! Create a graph of the total mass of metal (y-axis) vs. the total volume of metal on the (x-axis). Connect the data points plotted using the “best fit straight line.” The slope of this line equals the density of the metal. Use the graph to calculate the slope (density) for both metals. Record your estimated slope on your graph.
CALCULATIONS: (Remember to show ALL your work! Keep in mind the rules for calculating with significant figures.) 1. Calculate density for each data point from your experiment 2. Calculate your average experimental value for the density of metals
POST-LAB QUESTIONS: (Remember to show ALL your work!) 1. If the accepted value for the density of copper is 8.93g/cm3, what is the percent error of your calculation of the density of copper? 2. What mass of copper shot would have volume of 38.38 cm3? (Use the accepted density of copper for your calculations) 3. Why does copper sink in water? Do all metals sink in water? Explain & justify. You may wish to refer to the density tables in the reference section of your book to answer this question. 4. What volume would 85.50g of copper shot occupy? 5. If 50.0cm3 of one type of metal has a mass of 352g, is this metal copper? Explain.
CONCLUSIONS: What did you do? What did you learn? How successful was the lab? What might you do differently next time? Be sure to discuss the key concepts of density and water displacement and how each was discovered in this lab.
ERROR ANALYSIS: What could have caused error in your results? Why is your experimental value for the density of copper different from the known value?
LAB WRITE-UP (Due Wednesday 9/28 at Midnight on Turnitin.com) – Must be typed!