please finish result section. Make sure you test at least 2 plastics if you have access to samples for them.

Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 1 of 14 Lab 4: Sorting Plastics Procedure (Prelab 4 , 15 pts total) due in Canvas Saturday 5/1 Results (20 pts) due in Canvas Saturday 5/8 Presentation (30 pts) due in Canvas Saturday 5/15 Discussion Board Posts (5 pts) due in Canvas Saturday 5/22 PURPOSE & LAB O VERVIEW Your group’s task is to design, test, and present the results of a test method used to separate or sort the six types of common plastics . This test method will be limited to equipment provided in the “take home ” lab kit and common equipment & household chemicals available in your home. Your group will create a prediction flow chart and write a step -by -step test method for sorting the plas tics. The final test method used by your group must be pre -approved by your instructor. Each group member will perform the same test method independently, using their own plastic samples, while working “together”. This is meant to replicate an actual lab setting, where your group would work together at the same lab bench. The samples collected in the Introduction to Plastics lab, along with the unknown plastic sample from the chemistry lab kit, will be tested and the results documented in your lab not ebook. After completing the lab, your group will meet to combine and analyze the test results. Together, you will create a video presentation where you present your test method and the combined lab results. This will include a discussion of the results an d conclusions. Your goal is to develop a test sequence that can reliably separate the plastics into the six resin codes and to correctly identify the unknown samples in your lab kits. INTRODUCTION There are several methods for sorting and identifying polymers. This is a crucial step in every recycling operation, as mixed polymers are much more difficult to recycle or cannot be recycled at all. Fourier -transform infrared spectroscopy (FTIR) produces a spectrum which can be used Instructions before starting : 1. Read this entire hando ut and Writing Lab Reports before starting. 2. Begin the prelab writeup in your lab notebook in pen. a. Add this lab to the Table of Contents . b. Complete the Header Information at the top of the first page that covers this lab . Add page numbering to the top right corner of your lab notebook pages. c. I. Introduction : Write this in your own words. What is the overall goal of this lab? What are the major chemistry concepts involved in this lab? What are the major tasks involved in this lab? d. II. Procedure: Label the next section as Procedure . Leave it blank for now. As you work on the procedure with the rest of your group, you will fill in this section. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 2 of 14 like a finge rprint to identify polymers. However, FTIR lab equipment is expensive and not always accessible. You will use differences in the density of resin codes 1 through 6 to sort the plastics, and attempt to correctly identify a sample of unknown resin code. Objects with the same volume but different mass can have different densities. The way the molecules pack together, and their molecular mass have a significant effect on density. Some polymer chains can pack very tightly packed together whereas others canno t. This fact can be used to separate many of the common plastics by preparing several liquids, each with a different density, and observing whether each resin sample sinks, floats, or suspends. Objects that sink are denser than the liquid, objects that flo at are less dense, and objects that are suspended have a similar density to the liquid. Your team will decide which liquids to use , and devise a sorting scheme. It is suggested that you start by observing each plastic in room temperature water. Does it f loat or sink? Test the “floaters ” in a less -dense liquid and the sinkers in a denser liquid. A minimum of three test liquids is required; however, your team may decide that more test liquids are needed to ensure an accurate sorting method. The test metho d will also be used to identify the likely resin code of unknown samples. A list of common household liquids and their approximate densities are found in Table 1. Use these liquid densities, along with the expected density of each plastic resin code in Ta ble 2 to design your test method. The density of each test liquid used MUST be determined experimentally in the lab. Sample procedures that can be adapted for use by your team are found later in this handout. The float/sink behavior of each plastic sa mple is used to make inferences about the plastic’s density. Do not attempt to directly determine the density of each plastic sample, as the sample sizes are too small to provide reliable data. Table 1. Approximate Densit ies of Household Liquids (at approx. 22 oC) Liquid Density (g/mL) Water 1.00 Vegetable Oil (soybean) 0.92 Rubbing Alcohol: 70% by volume isopropyl alcohol (IPA) in water 0.86 Sucrose (table sugar) solution: 60% by mass in water 1.29 NaCl solution: ~26% by mass in water Note: Kosher salt is pure NaCl; “table salt ” commonly has other additives. 1.20 Corn syrup 1.48 Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 3 of 14 Table 2. Densities # of common polymers. Resin Code Polymer Density (g/mL) 1 polyethylene terephthalate (PETE or PET) 1.38 – 1.39 2 high -density polyethylene (HDPE) 0.95 –0.97 3 Polyvinyl chloride (PVC) 1.16 – 1.35 4 low -density polyethylene (LDPE) 0.92 – 0.94 5 Polypropylene (PP) 0.90 – 0.91 6 Polystyrene (PS) 1.05 –1.07 7 Other plastics, i.e., Polylactic acid (PLA) 1.25 – 1.26* * for PLA only. # Brandrup, J., Immegut, E. H., Grulke, E. A., Eds., Polymer Handbook, 4th ed.; John Wiley and Sons: New York, 1999. Using Electronic Balances and Scales In most laboratories, an electronic balance is used. These measures the mass of a sample as the balance is not affected by gravity. Your lab kit contains a n electronic scale and measures weight , as it is affected by gravity. Below are g ood practices to follow when using an electronic balance or scale: • Put chemicals that can damage the measuring pan in a container , rather than directly on it. A glass container, such as a beaker, or a plastic container, such as a weigh boat, can be used. • Avoid spilling chemicals onto the measuring pan by remov ing the container (e.g. weigh boat) from the pan before adding the chemical. The balance or scale will remember the mass of the container until it is tared again. • Do not weigh hot objects; objects should always be near room temperature. • Avoid bumping the balance/scale or the surface it is on. This can cause the reading to fluctuate. • Check that the balance/scale is calibrated before use. Once calibrated, avoid moving it, as this can invalidate the calibration. Volum e It is important to realize that different glassware is used for different purposes. Some glassware is used to simply hold approximate volumes of a liquid, e.g. a beaker or Erlenmeyer flask. More -precise glassware is used when precise volume measurements are required, e.g. a graduated cylinder or volumetric flask. Graduated cylinders, volumetric flasks, pipettes (a lso spelled pipets ), and burets are examples of glassware used to measure volumes. The disposable plastic pipets included in your kit are not reliable measuring devices. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 4 of 14 Measurement of liquid volumes is frequently complicated by the meniscus. Water in a small glass tube may curve as shown in Figure 1. Attraction to the glass causes a small amount of water to creep up the side of the container, creating a curved surface. This surface shape is a concave meniscus. Always measure a volume at the bottom of the meniscus or liquid . The angle of reading can also affect the accuracy of the volume being measured. To ensure the most accurate reading, put the graduated cylinder on a flat surface and always read the meniscus at eye level (you may need to bend down). Use/re -use of a di sposable plastic pipet A small disposable plastic pipet can be a helpful lab tool for delivering a very small amount of liquid. Rather than being “single use” plastic items, they can be reused if you are careful. Each time a pipet is used with a differen t liquid, rinse the pipet at least three times with a small amount of the new liquid. Multiple and careful rinsing ensures that any liquid that remains in the pipet is only the new liquid . This works well for water or aqueous solutions, but not for oily liquids. Making a solution by dissolving a solid in a solvent Use Table 3 as a guide for preparing a sugar or salt solution of specific density. Start by calculating the amount of solute needed for the desired amount of total solution. Recall that % by mass is: % by mass = ℎ ℎ 100% Sample Calculation Table 3 shows that an aqueous NaCl solution with a density of 1.132 g/mL is 18.0% by mass NaCl. This means that there are 18.0 grams of NaCl for every 100 grams of total solution (NaCl and water). Let’s say the goal is to make 150.0 grams of an 18.0% solution (density of 1.132 g/mL). The first step is to calculate the amount of NaCl needed. Start with the 150.0 grams of solution you wish to make and multiply by the mass percent, as a fraction: 150.0 grams solution x 18 .0 100 = 27.0 grams NaCl This tells us to add water to 27.0 grams of NaCl until the total solution weighs 150.0 grams. If the NaCl is fully dissolved in the water, the final solution has a density very close to 1.132 g/mL. Fig . 1: Reading the meniscus of a liquid in a graduated cylinder . Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 5 of 14 Table 3. Density # and percent by mass for aqueous solutions of NaCl and sucrose (table sugar). Density (g/mL) % NaCl by mass Density (g/mL) % NaCl by mass Density (g/mL) % Sucrose by mass Density (g/mL) % Sucrose by mass 1.101 14.0 1.164 22.0 1.038 10.0 1.229 50.0 1.116 16.0 1.180 24.0 1.081 20.0 1.286 60.0 1.132 18.0 1.197 26.0 1.127 30.0 1.347 70.0 1.148 20.0 1.176 40.0 #Reference: Handbook of Chemistry and Physics, 87 th Edition, David R. Lide, Ed.k, 2006 – 2007 Creating a solution by combining two miscible liquids When two liquids are completely soluble in each other and form a homogenous mixture, they are miscible . A mixture of two miscible liquids has a density between that of the two pure liquids. For example, combining volumes o f water ( 1.00 g/mL) and pure isopropyl alcohol (0.786 g/mL), creates a solution of intermediate density. Figure 2 shows how solution density varies with percent by mass isopropyl alcohol (IPA) in water. It is important to realize that rubbing alcohol i s purchased in percent by volume IPA in water. For reference, a 70% by volume IPA is approximately 63% by mass IPA. Fig . 2. Density of aqueous isopropyl alcohol mixtures at 20.0 oC. Reference: Lide, 79th Edition CRC Handbook of Chemistry and Physics, p. 8 -75, (1998 -1999) Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 6 of 14 Sample Calculation Changing 91.0% by volume IPA to 70.0% by volume IPA You may find that some team members have a 70% IPA solution, and others have another concentration, perhaps, 91.0%. Ideally , all team members will use the same concentration, so in this case, those with the 91.0% should dilute their solutions to 70.0%. Decide on the total amount of dilute solution needed. Calculate the amount of concentrated solution needed for the dilution. A sample calculation is shown below for making 100.0 mL of 70.0% =PA, by diluting 91.0% =PA. (You will learn about this later in the quarter.) “C” refers to concentration and “V” refers to volume. ‘1’ indicates the dilute solution and ‘2’ indicates the co ncentrated solution. C1V1 = C 2V2 (100.0mL)(70.0%) = X(91.0%) X = 76.9 mL This tells us to measure 76.0 mL of 91.0% IPA and then add water until the final volume is 100.0 mL. IMPORTANT: volumes are NOT additive, so measuring 76.0 mL and 24.0 mL and combining them will not give exactly 100.0 mL. TASKS There are three main parts to this lab that must be done as a group: 1. Procedure (“Prelab 4”, due Sat 5/1) : Planning and writing of your group’s method of sorting the plastic samples your group collected at the end of the previous lab. Approval must be obtained by the instructor before moving on to the next part of the lab. 2. Results (“Lab 4 Results”, due Sat 5/8) : Data collection, following your group’s approved method of sorting the plastic samples (see #1 above). 3. Analysis (“Lab 4 Presentation”, due Sat 5/15) : Group presentation of the results, summarizing your group’s findings and conducting an error analys is. See below for more details on each of these parts. PROCEDURE – due on Canvas as the “Prelab 4” assignment on Sat 5/1 The goal is to devise a sorting method to sort plastic samples in resin codes 1 through 6 and correctly identify the unknown plastic samples. Consider the equipment and materials that each group member has available (refer to the end of the Intro to Plastics lab). All group members should perform the same tests; however, there may be equipment/ materials limitations. Discuss any concerns or issues with your instructor as you develop the group’s plan. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 7 of 14 Safety Considerations The solutions (Table 1) used in this experiment are commonly found in households. However, this does not mean they do not have hazards associated with them. • Safety goggles are required for eye protection when working with glassware and chemicals. Glassware can shatter; chemical can spill and splash. Both can cause irreversible eye damage. Safety goggles are included in the kit. • Rubbing alcohol (contains isopropyl alcohol) can be harmful if not used properly and in a well -ventilated area. It is also flammable, so keep away from heat. Read and follow the label warnings carefully. Read the SDS for this chemical. Flowchart of the Test Method Discuss and devise a method to separate the plastic samples by observing which samples sink, float, or suspend in test liquids. As a suggestion, start by testing all samples in water, then separate the sinkers from the floaters and test them similarly in liquids with different density. Refer to Table 1 for suggested liquids to use , and Tab le 2 for the typical plastic densities. A minimum of three test liquids is required. Create a flow chart to illustrate the test method. Figure 3 shows an example flow chart. It is intentionally incomplete, as you must design the remaining parts of the flow chart. Y our flowchart needs to include all planned tests. Fig . 3. Example of a test method flowchart . The notes in parentheses such as “1: PET” indicate your group’s predictions of the float/sink behavior of each plastic type. Making predictions This step is important , as it helps refine and gain confidence in your sorting test method. In addition, you will revisit these predictions when discussing the results in the lab presentation. On your flowchart, add predictions for the resin codes , whether they will float or sink in each test liquid, e.g. 1: PETE . (e.g., 1: PET) (e.g., 1: PET) (e.g., 1: PET) (e.g., 1: PET) (e.g., 1: PET) (e.g., 1: PET) Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 8 of 14 Writing a Procedure Once your team has decided on a test method and flowchart, collaboratively write the procedure to follow. Sample procedures for specific tasks are provided in the Appendix. Modify these as nee ded. Ensure they are written so each team member can follow them AND so that another chemistry student could repeat the same tests in the same sequence. The procedure must include the following four components : • Flow chart , similar to Figure 3. • Safety Section : Describe all safety hazards and how you will protect yourself from them, e.g. wear safety goggles, work in a ventilated area. • List of Materials : List the specific equipment, materials and household chemicals needed. • Step -by -step Procedure : Use your flowchart as a guide but convert it to a step -by -step procedure. a. Include the equipment (specific measuring devices or containers), and chemicals or substances used in each step. b. Describe how to prepare the plastic samples. c. Describe exactly how to prepare or make the test liquids. d. Describe exactly how to measure the density of each liquid. e. Describe exactly how to complete the density float/sink tests . Be specific and include enough detail so that someone else could perform each test. f. Include directions for recording each measured value or qualitative observation, as well as any calculations that are needed. Procedure submission All students in the group should have the same flow chart and procedure written in their lab notebooks. Select ONE student in the group to submit a pdf copy of the group procedure in the Prelab 4 assignment page on Canvas by the due date . The procedure must include all four components listed in the previous section : • Flow chart (2 pts) • Safety section (2 pts) • List of materials (2 pts) • Step -by -step procedure (9 pts) All students in the group will receive the same Prelab 4 grade. After submission, your instructor will review the procedure, and provide comments. Note that depending on the comments, a revision and resubmission of the revised procedure may be required, before continuing on to the data collection. RESULTS – due on Canvas as the “Lab 4 Results” assignment on Sat 5/8 IMPORTANT : Being prepared and organized is key to your success. I f your instructor can’t decipher your lab work, it will negatively impact your grade. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 9 of 14 1. Have the approved team procedure available in your own lab notebook, so that you can follow it. 2. After the procedure in your lab notebook, label a new section called Results . 3. You may find that the procedure must change as you perform the lab. This is perfectly acceptable and really happens in research labs! Document (and label) any changes under a subtitle, Procedure Notes . However, you MUST ensure that no new safety hazard s are introduced by any changes. 4. Construct properly -formatted data tables in your lab notebook, leaving space for the Procedure Notes . Note that in order to create the data tables correctly, you must think ahead of all the data your group will be collecti ng. See Tables 4 and 5, below, as examples; they may need to be modified, depending on your group’s flow chart/procedure. 5. As a group , p erform your group procedure on the plastic samples collected by your group . Record ing all measured values and test results directly in the data table s. Do not use scratch paper to record your results! Split up the work equitably ; record who did what in your lab notebook in your Procedure Notes section . 6. On your own , perform your group procedure on your unknown plastic sample that was included in your kit (record the unknown number in your lab notebook!) . Record the unknown sample’s data in the same data tables. 7. Below the data tab les, create a section called Calculations . In this section, neatly show your work for any needed calculations, such as solution density. Label each calculation , so others can decipher your work. Results submission Each student must individually submit a pdf copy of the results in the Lab 4 Results assignment page on Canvas by the due date. The results must include the following components: • Procedure Notes section, with notes (3 pts); • Group data for the group plastic samples, organized in data tables (7 pts); • Individual data for your own unknown sample (you are responsible for having your unknown’s data in your own lab notebook! (2 pts) Test Solution Mass (g) Volume (mL) Solution density (g/ml) Test Solution Samples that Floated Samples that Sunk Samples that Suspended Table 4. Example of a density data table . Table 5. Example of a float/ sink test data table (modify as needed) . Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 10 of 14 • Calculations section (8 pts) Each student will receive their own results grade. After submission, your instructor will review the data and calculations , and provide comments. Note that depending on the comments, a revision and resubmission of the revised procedure may be required, before continuing on to the presentation . PRESENTATIONS – due on Canvas in the Lab 4 Presentations Discussion Forum , Sat 5/15 Divid ing the work equitably , assign one or more group member s to prepare and present the sections below in PowerPoint . Each section must identify which group member(s) worked on it , by including a small note in the corner of the first slide for each section . (20 pts) PowerPoint Presentation 1. (2 pts) Title slide . It should include: Title of Experiment Names of Team Members Purpose of the Experiment (refer to Writing Lab Reports when writing this) 2. (9 pts) Results slides. A. Results Tables • Test liquid density : Create an organized Table (using MS Word , Excel or equivalent) that shows the experimental density for each liquid used in the test method . Paste the table into PowerPoint. - Include the mass, volume, density for each individual result (e.g. 4 trials if 4 measurements were done on a particular liquid ) - Include the average experimental density (identify any outliers that were not used for the average) - Report the correct sig figs and units for all values. - Include the expected densities (from Table 1 or 3). • Float/ sink tests : Create a second Table that shows the results of the known resin codes and the unknown samples ( include =D #’s) in each test liquid. - Include the results of all group members. - Identify any known resin code results that are suspected outliers. B. Flow chart s for known and unknown samples in float/ sink tests • Create a second flow chart that shows the results for the known resin codes , and for all of the unknown samples for the group (include ID # ’s). This should be very similar to the prediction flowchart created with the procedure. • Identify and eliminate any outliers. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 11 of 14 3. (9 pts) Slides that d iscuss the results of the o verall sorting method . • Discuss the experimental liquid densities. How do the average results compare to the expected values? What potential experimental errors could explain any differences? Do the errors appear to be systematic or random? • Explain any outliers . W hat experime ntal errors could have caused these? • Compare the sorting method test results to the original predictions. Were the predictions correct? Explain any differences. Were they caused by experimental errors ? Do the predictions need to be revised? • Which resi n codes were reliably sorted and how do you know this? • Which resin codes were not reliably sorted? Explain any issues that arose. • What is the likely identi ties of each unknown plastic sample? What is the confidence in each identification? How do the t est results support each identification? • What changes could be made to improve this sorting method? • Optional: Suggest additional experimental work or studies that would extend knowledge in the sorting of plastics. (10 pts) Once the group’s PowerPoint file is finished, c reate a 5 to 7 -minute (suggested length) video in which your group presents the PowerPoint file. This presentation can take on many forms, however you will need to post a link to your video in the Lab 4 Presentat ions discussion forum on Canvas by the due date . Your instructor will provide you with posting instructions. • Each group member must participate equitably in the presentation. • Every group member must speak at some point during the presentation. Do not simply read off of the PowerPoint file! Make sure that the audio can be heard, and is in sync with the presentation slides. • Suggested presentation formats include (but are not li mited to) : - A voice over the PowerPoint presentation , recording through PowerPoint . - Use Panopto to record the video . See the Panopto Recordings link on the left side of the Canvas window. - Record your presentation while in a Zoom meeting room , screenshari ng the PowerPoint . - If you have another preferred format, ask your instructor for approval before starting. The videos must be uploaded to Panopto fo r posting in the discussion boar d. In the discussion board, you can provide either the link from Panopto to the video, or embed the Panopto video in your discussion board post. DISCUSSION BOARD POSTS – due on Canvas in the Lab 4 Presentations Discussion Forum, Sat 5/22 Each student must watch the presentations of two other groups , and post comments to each that include: • What did you like most about the team presentation? • What questions do you have after watching this presentation? Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 12 of 14 Appendix Sample Procedures: Modify these as needed. Combine them in a sequence that make sense for your test method. Add procedure steps as needed. Preparing Plastic Test Samples 1. Prepare test samples by cutting similar size plastic pieces for each resin code. Avoid including paper for plastic labels that may be present on the samples used. Approximately 2 cm x 2 cm samples are recommended. However, if all samples are similar in color, use different shapes to identify each one. 2. Record initial (pre -test) observations for each plas tic sample. What shape is it? Is it clear? cloudy? color? Is it flexible? brittle? thick? thin? CAUTION: Be careful when cutting plastic pieces; don’t cut yourself. =f the sample is too thick to cut safely, find one that is thinner. Weighing by taring 1. Always wear safety goggles and identify any hazards from the chemical safety data sheet. 2. Calibrate the scale before using. (Include the procedure provided by the manufacturer here). 3. Place the empty container or weigh boat in the cente r of the measuring pan. Press the zero (or tare) button and wait until the reading displays only zeros. This is called taring . 4. Now, add the chemical to the empty container and place it back on the tared scale. 5. Wait until the reading stabilizes and record all digits displayed (be sure it is set to display in grams). If the last digit is randomly fluctuating, record an average val ue. Record this value as the weight of the chemical. Weighing by difference 1. Always wear safety goggles and identify any hazards from the chemical safety data sheet. 2. Calibrate the scale before using. (Include the procedure provided by the manufacturer here). 3. Press the zero button and ensure the reading displays only zeros. 4. Place the empty container in the center of the measuring pan. Wait until the reading stabilizes and record all digits displayed. Record this value as the weight of the empty containe r. 5. Remove the container from the scale and add the chemical to the container. 6. Check that the display reads only zeros, then place the container + chemical on the pan. Wait until the reading stabilizes and record all digits displayed. Record this value as the weight of the container + chemical. 7. Subtract the weight of the container from the weight of the container + chemical and record this as the weight of the chemical. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 13 of 14 Float/Sink Testing Note: Be sure to first determine the density of each liquid used in the float/sink tests. Plastic samples should not be thin films or bags. 1. Wear safety googles. 2. Add approximately 150 – 200 mL of each test solution to a separate, clean, dry and transparent container (such as a drinking glass). Label each container with the name of the solution it contains. Cover any isopropyl alcohol solutions to prevent evaporation. 3. Fill one additional beaker/container with just water. Label this as “rinse water ”. 4. Add a known plastic to the liquid and vigorously stir to remove any air bubbles that may influence float/sink behavior. 5. Wait approximately 30 seconds them make observation s. Record whether the sample, floats, sinks, or suspends. 6. Remove the sample from the test liquid, rinse it in water, then wipe it dry. Note: samples tested in oil should not be rinsed in the water. 7. Repeat steps 4 through 6 for each plastic sample. Making an aqueous salt or sugar solution (modify this based on the total amount and density of solution needed) Part 1 - Make the Solution (150 grams of an 18.0% by mass NaCl solution) 1. Always wear safety goggles and identify any hazards from the chemical s afety data sheet. 2. Put at least 200 mL of tap water into a clean container and let it come to room temperature. 3. Calibrate the scale (include the manufacturer’s directions here). 4. Place a clean, dry 250 mL beaker or similar container on the scale and tare it (zero it). 5. Add exactly 18.0 grams NaCl to the container. Record the NaCl weight in a data table. 6. Remove the container with NaCl from the scale. Add approximately 100 mL of room temperature water (approx. 100 grams). Stir until the NaCl completely d issolves. If needed add more water, however do not exceed a total weight of 150.0 grams. 7. Weigh the NaCl solution and beaker and record the weight. Add small amounts of water until the total weight is 150.0 grams. Record the final weight. 8. Stir again to ensure the solution is homogeneous and that all NaCl is dissolved. Part 2 – Determine the density of the prepared solution 1. Zero the scale and then record the weight of a clean, dry 100 mL graduated cylinder. 2. Remove the graduated cylinder from the scale and add approximately 25 mL of the solution to the 100 mL graduated cylinder. Record the actual volume (include all sig figs!). 3. Record the weight of the graduated cylinder and the solution. 4. Calculate the density: divide the weight of the solution (weight grad. cylinder + solution – weight grad. cylinder) by the solution volume. 5. Compare this to the desired density (1.132 g/mL acco rding to Table 2). If it is outside of your group ’s acceptable measurement error, re -make the solution. Lab 4: Sorting Chemistry &161 Spring 2021 Plastics General Chemistry with Lab 1 Duldulao Green River College – Updated 4/25/2021 Page 14 of 14 Diluting an aqueous solution The example below is for 91% by volume IPA diluted to 70% by volume IPA 1. Safety precautions : Wear safety goggles and wo rk quickly to minimize evaporation of the isopropyl alcohol (IPA). IPA solutions are flammable; keep these away from heat sources or sources of ignition. Work in a well -ventilated area and avoid breathing the fumes. 2. Add exactly 76.9 mL of 70.0% IPA to a c lean dry graduated cylinder. Use a clean pipet to add the last amount of solution to ensure accuracy. 3. Add water to the graduated cylinder until the total volume is exactly 100.0 mL. Use a clean pipet again to add the final amount of water. Be sure to cle an the pipet by rinsing it at least three times with water. 4. Cover the solution to prevent evaporation of the IPA, as this will change its density! Determine the density of the diluted solution 5. Zero the scale and then record the weight of a clean, dry 100 mL graduated cylinder. 6. Remove the graduated cylinder from the scale and add approximately 25 mL of the solution to the 100 mL graduated cylinder. Record the actual volume (include all sig figs! ). 7. Remove the graduated cylinder from the scale and add approximately 25 mL of the solution to the 100 mL graduated cylinder. Record the actual volume (include all sig figs!). 8. Record the weight of the graduated cylinder and the solution. 9. Calculate the d ensity: divide the weight of the solution (weight grad. cylinder + solution – weight grad. cylinder) by the solution volume. 10. Waste disposal : Since this is not performed in an academic or industrial setting, IPA solutions can be disposed of in a resident ial drain due to exemptions from hazardous waste disposal regulations (in the U.S.). Run the tap water afterwards to fully rinse the solution down the drain.