AP CHEMISTRY LAB FIRST PLASTICS LAB Discussion: In the world in which you live, there are many man-made plastics. There are a number of reasons why they are so prevalent in our society; they are cheaper and easier to produce than natural materials, they withstand a number of different environments without breaking down, they can be molded and formed into seemingly unlimited shapes and textures, and they can be used to serve a number of different functions. Some of the same characteristics that make plastics so useful can also be a major problem if we consider thesee substances from a different point of view. Most of them have a petroleum base. As you know petroleum is a nonwithstand a renewable resource. Since plastics do number of different environments, they do not break down on their own. (They are usually non-biodegradable.) Once we make them, they will be with us for a long time! Some plastics produce nocuous fumes when they are burned. Chemists are instrumental in helping to find and produce more and different plastics that can be used in many ways. Examples range from nylon to thermofil to bulletproof fabrics. Hopefully those plastics will help to improve our lives, but, chemists can also be involved in a different way with plastics. They can help identify the types of plastics that have been produced and have fulfilled their primary function. We as chemists can study them and find ways to recycle them. This will be our job today. You, the chemist, will be asked to identify six types of plastics, find their properties and develop a method for identifying and classifying them. Once we know their properties we should be able to identify an unknown sample. So, here goes! Procedure: Before you come to class to do this lab, you should have read the entire lab and should have constructed a data table for part I of the lab. Obtain 3 or 4 samples of each of the different types of plastics. Make sure you label them and keep track of which sample is which! 1
Part I Water test Half fill a 150 ml beaker with tap water. Place a sample of each type of plastic in the water. Poke the pieces of plastic with a stir rod to dislodge any adhering bubbles of air. Try to make the pieces of plastic sink. From this test, how do you think that the density of each type of plastic compares to water? Clean up your area when you are done recording your results. To save time you can start heating the water in another 150 ml beaker for the hot water test. Remember, plastics do not dissolve in water so do not pour them down the sink. You can dry them and use them in another test. Heat test Using a tongs, hold the sample of plastic in boiling water for 30 seconds. Press the sample between your fingers to see if it has softened in the boiling water. If the sample softens, discard the sample in the trash. If you do not observe any changes, dry the sample so it can be used in another test. Oil test Half fill a 150 ml beaker with cooking oil. (If one of your neighbors has oil measured out already, you can use their sample after they are through with this test. In other words, look to conserve materials for RT!) Place a sample of each type of plastic in the oil. Poke the pieces of plastic with a stir rod to dislodge any adhering bubbles of air. Try to make the pieces of plastic sink. From this test, how do you think that the density of each type of plastic compares to oil? Clean up your area when you are done recording your results. Check with your neighbors to see if they can use the oil beaker before you return the oil to its container. Two things to remember here: A) oil and water don t mix! Don t pour the oil down the sink. B) plastics, like oils, do not dissolve in water so do not pour them down the sink. You can dry your samples off and use them in another test. Isopropyl alcohol test Half fill a 150 ml beaker with 70 % isopropyl alcohol. (If one of your neighbors has alcohol measured out already, you can use their sample after they are through with this test; remember, materials conservation.) Place a sample of each type of plastic in the alcohol. Poke the pieces of plastic with a stir rod to remove any adhering bubbles of air. Try to make the pieces of plastic sink. From this test, how do you think that the density of each type of plastic compares to alcohol? Clean up your area when you have completed recording your results. Check with your neighbors to see if they can use the alcohol beaker before you return the alcohol to the designated container. Remember, plastics do not dissolve in water so do not pour them down the sink. You can dry them and use them in another test. 2
Acetone test (This test is to be conducted in the hood. Acetone is quite flammable, so do not have a burner going in the hood at this time!) Pour 25 to 50 ml of acetone into a 150 ml beaker. Using tongs, place your sample in the acetone for 20 seconds. Remove the plastic from the acetone and press if firmly between your fingers. The polymer chains may loosen up and feel soft and sticky. Try to scrape off some plastic with your fingernail. If you are wearing fingernail polish, you should have a friend do this test for you. Acetone is one type of fingernail polish remover. There may not be a reaction to this scrape test. Discard the sample in the trash. Make sure you cover the acetone container with a Petri dish before you leave the hood area. Copper wire test Grasp the copper wire by the insulated end. Hold the bare end of the wire in the hot part of a Bunsen burner flame until the wire is red hot and the color of the flame looks like a normal Bunsen burner flame. Be careful! Do not touch the hot wire to your skin! Remove the wire from the flame and quickly touch it to the plastic sample. Some of the sample should stick to the wire, but not the entire piece. Place the wire with the glob of plastic back into the flame. Record any changes that you see in the flame. Allow the wire to cool and then clean up your area. Discard the plastic samples in the trash. Clean up Check your area over again, to make sure that it is clean. Return any of the test solutions to their appropriate containers, and any unused samples of plastic to their correct jar. Part II Before you proceed with this part, develop a flow chart using the different properties observed in Part I and have RT initial it. The purpose of the flow chart is to allow you to identify the different types of plastics with which you have been working. You need to obtain a sample of an unknown form RT to check to see if your flow chart is valid. A major part of the grade for this lab will be determined by how well you identify your unknown, so Good Luck! Obtain an unknown sample of plastic from RT. Make sure that you and he have recorded the number of the unknown. Run the necessary tests on your sample so that you can identify the type of plastic that you have. When you think that you have all of your observations for your unknown recorded, and from them have correctly identified your sample, bring your sample back to RT to have the identification of your unknown confirmed. 3
Part III Experimental design section: Design an experiment to measure the density of one of the liquids used in this lab. Write out an outline telling what you need to do and the equipment you will use. Remember, the precision of the density you will compute is dependent upon the least precise measurement you take. Therefore, you need to thank carefully about how you measure the volume and the mass of your sample. Coordinate your work with the other members of the class so that each liquid will have its density checked. Have your procedure OKed by RT and then carry it out. Show your data and calculations clearly in this lab report. That means that you numbers need labels and units! Share your data with your classmates. Set up a data table so that you can clearly see the density of each solution. It would really be convent if the densities were listed from either the most to the least dense, or vise versa. Questions: 1) What types of plastics float in water? Why? 2) What kind of plastic would you not want to use to contain hot liquids like hot coffee? 3) Jan wanted to give some of her fingernail polish remover to one of her friends. She poured part of that solution into an old soda bottle and started to her friend s house. Halfway there she noticed that she had a mess on the floor of her car where she had placed the soda bottle. What kind of plastic was used to construct the soda bottle? 4) Refer to the density section of the lab and your observations. Now, give the approximate range of densities for each type of plastic used in this lab. 5) Why did you have to be careful to remove the air bubbles from the plastic when you ran the density tests? 6) Why couldn t samples of LDPE and PP be identified with only the water density test? 7) Go to your text and define: A) Monomer B) Dimer C) Polymer 4
8) Below are the recycle symbols for each type of plastic and the initials for each. Go to the polymer chapter in your text and or references provided by RT. Find the monometer for each kind of plastic. Hint: one of the plastics we used is called Nylon 66 in industry. That s its trade name. Make sure you indicate which one of these plastics it is and give the name of its monomer(s). http://www.thedailygreen.com/green-homes/latest/recycling-symbols-plastics-460321 http://www.gcsescience.com/o56.htm http://www.chemguide.co.uk/organicprops/esters/polyesters.html http://pslc.ws/macrog/kidsmac/polysty.htm http://www.chemheritage.org/educationalservices/nylon/chem/name.html Source: Adapted from Hands On Plastics: A Scientific Investigation Kit, a joint project between the American Plastics Council and National Middle Level Science Teachers Association 5