CHE121 W1 Lab 1 - Investigating Density PDF

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Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

Background: You have a summer internship working in a jewelry laboratory where your job is to explore the properties of some alloys (mixtures of metals) of silver, rhodium and platinum in order to make brighter jewels at a lower cost. One day, while preparing an alloy, you accidentally left the bottles near the melting furnace and the labels became charred (burned) and unreadable. OH NO! You now have three unlabeled bottles of metallic powder. Your task is to perform experiments to identify the metals in these bottles before your supervisor returns. From a chemical handbook available in your lab, you find that the densities of silver, rhodium and platinum are 10.5, 12.4 and 21.45 grams per cubic centimeter, respectively. There are several objectives of this lab: 1. Orient yourself with the virtual lab environment. 2. Practice computing the densities of unknown objects. 3. Practice recording data and taking notes from experimental procedures. 4. Analyze data to make valid scientific conclusions. The procedure below is but one way to perform the following lab experiment. As you work through the experiments, consider other ways that you may possibly carry out each step or even propose a new lab procedure in your report. Record any necessary notes and data in the pages that follow the procedure below. Write your report using the guidelines at the end of this document.

Procedure: Preparing the Lab 1. From the course home page, click on the Virtual Lab Tutorial link to watch the overview of using the virtual lab. 2. From the course home page, access the lab environment by clicking on the Virtual Lab link. 3. After the lab environment loads, click ‘File’ then ‘Load an Assignment.’ 4. Select the ‘Molarity and Density’ category. 5. Select the ‘Metals Density Problem’ assignment. 6. At this point, you have prepared the laboratory with the require supplies to complete your experiments. Page 1 of 6 Copyright GMC

Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

Performing the Experiments 1. Select the ‘Solutions’ tab if it is not already selected. You should now see four items including the distilled water and the three unknown metals. If not, verify that you have selected the correct assignment by following the steps in the “Preparing the Lab” section again. 2. Place the unknown ‘Metal 1’ onto the workbench by clicking on it. 3. We will also need a balance (scale) and weigh boat. Add these items to the workbench by locating them in the ‘Tools’ and ‘Glassware’ tabs, respectively. 4. Ensure the scale has been tared (or ‘zeroed out’) by verifying zero mass being shown on its display. 5. Add the weigh boat to the scale and record its mass. Then, tare the scale again so that we can negate the mass of the weigh boat when obtaining the mass of the unknown sample. 6. Click and drag the ‘Metal 1’ sample to the weigh boat. A dialog box should appear like the one shown below:

Figure 1: Dialog box that appears when the metal’s container is dragged to the weigh boat. 7. We want to use an amount in the range of 3-15 grams of our unknown metal. Click the ‘Hold to Pour’ button several times until we have dispensed an amount within the desired range. If you dispense too much of the metal, you will need to restart by removing the scale and weigh boat (by right-clicking and selecting ‘Remove’). Record the mass of your unknown in the table for Metal 1 data below. 8. Acquire the 10 mL graduated cylinder and 250 mL beaker from the ‘Glassware’ tab and place on the workbench.

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Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

9. Place the distilled water onto the workbench. 10. Fill the 250 mL beaker with distilled water clicking and dragging the water to the beaker. A similar dialog box as in Step 6 will appear allowing you to fill the beaker. Note: In a real lab, we cannot transfer water to the graduate cylinder directly from the bulk water container because it will dispense too much too quickly! 11. Transfer a small amount of distilled water in the range of 2-7 mL to the 10 mL graduated cylinder from the beaker by clicking and dragging the beaker to the graduated cylinder. If you add too much, right-click and click ‘Remove’ to start over. Record this initial volume in the table for Metal 1 data below. 12. Right-click on the graduated cylinder and click ‘Detailed View’ to take a closer look and view the graduations on the cylinder. 13. Transfer your measured amount of metal powder to graduated cylinder. Record this final volume in the table for Metal 1 data below. 14. Ensure that you have recorded all needed date and clear the workbench by right-clicking on an empty area in the workbench and selecting ‘Clear Workbench.” 15. Compute the density of Metal 1 from your collected data and record it in the table for Metal 1 data below. 16. Repeat the procedure to collect density data for two more trials of Metal 1. 17. Repeat the procedure to collect density date for three trials each for Metal 2 and Metal 3.

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Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

Notes This section should include notes about any observations or data collected during the lab.

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Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

Data This section will include all data collected during the lab.

Unknown Metal 1 Data Measurement (variable) Mass of metal (m1) Initial Volume (Vi) Final Volume (Vf) Density (D)

Trial 1

Trial 2

Trial 3

Average Density

Unknown Metal 2 Data Measurement (variable) Mass of metal (m2) Initial Volume (Vi) Final Volume (Vf) Density (D)

Trial 1

Trial 2

Trial 3

Average Density

Unknown Metal 3 Data Measurement (variable) Mass of metal (m3) Initial Volume (Vi) Final Volume (Vf) Density (D)

Trial 1

Trial 2

Trial 3

Average Density

*Note: You can copy and paste your data tables into your report later.

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Laboratory 1 Procedure – Investigating Density CHE-121: Principles of Chemistry 1

Report Requirements This section contains key information that must be included in your typed report. 1. Define the problem in a manner that is clear and insightful. 2. Identification of the strategies used during the lab. 3. Clear hypothesis statement and other potential solutions that identify any relevant contextual factors (i.e. real-world costs). 4. Clear presentation of data including any tables or other figures that are relevant to understanding your stated conclusions at the end of the report. 5. Clearly stated results (proper identification of all three metals) and discussion possible improvements to the procedure. 6. Conclusive statements arguing in favor of your findings. Note: All reports will be graded using the rubric embedded within the course.

Here are some questions to consider as you write your report: 1. 2. 3. 4. 5. 6.

Does my problem statement make sense? Have I summarized my strategies/procedures well enough to be replicated by an outsider? Did I have a valid hypothesis at the start of the lab? Have I expressed this in my report? Do my tables and/or graphs make sense? Are my conclusions valid based on my supplied data? Did I thoroughly summarize my laboratory experience in a concise, factual way such that the reader can understand my processes and findings in the conclusion section alone?

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