8th grade integrated Science Standard I, objective 4
Title: Properties of Plastics
Description: Students will test the different kinds of plastic to determine the physical and chemical properties of each and predict what each might be used for. They will identify the number of an “unknown” plastic. An inquiry approach could be substituted to allow students to develop their own tests.
Materials: numbered plastic (students can bring from home), paper clip, acetone (fingernail polish remover will work), denatured alcohol, hot water, 250 mL beaker, tweezers plastic vials, goggles, salt, 3 clear glass or plastic vials or small beakers per group. Reading selection (see below)
Time Needed: 10-15 minutes for day 1, 50 minutes for day 2
Safety Issues: Students should not have the denatured alcohol near an open fame. Hot water should be handled with care.
Procedures: Day 1 1. Ask students what a computer case would be made of if there were no plastics. The first “Apple” computer had a wooden apple crate as the outside casing. They may come up with answers but no other substance has the properties of plastic that make it so flexible, strong and lightweight. 2. Handout the student sheet and read the introduction with students. If you are going to ask them to bring in plastics, give that assignment now. You might collect some of the higher number plastics yourself because it is less likely that students will find these at home. Do not test plastic #7, it contains BPA, now thought to be hazardous under some circumstances. 3. Cut into narrow strips the plastics that you have and place in contains labeled with the plastics’ number. Assemble other materials. Pick one plastic to be the “unknown” Day 2 1. Read the lab procedures with students and describe the location of materials. 2. Collect any plastics the student shave brought in and cut pieces to use if needed. 3. All students time to work on the lab. 4. As students finish, hand out “Know Your Plastic Recycling Number?” reading. Have students complete their data tables with this information.
Scoring Guide 1. student brings in plastic (if assigned)……………………………………4 2. student follows all lab procedures……………………………………….4 3. analysis questions and conclusion thoughtfully responded to……….4 Student Sheet
Title: Properties of Plastics name______
Introduction: The scientific discovery of plastics has revolutionized how people build and use materials. Plastics have properties that allow them to be lightweight, strong and flexible. In this activity you will see how plastics vary in the way they react to different tests. After you identify their properties, you will see if you can identify an unknown plastic. Good Luck!
Do you understand what this symbol, number and letters mean?
Materials: plastic pieces, paper clip, denatured alcohol, acetone, beakers, salt, 4 glass vials, boiling water, tweezers, goggles
Procedure: Part I 1. Find the density of each plastic piece. Start by labeling the vials 1,2,3 and 4. 2. Add 10 ml denatured alcohol into vial 1. Fill vial 2 with 5 ml of water and 5 ml of alcohol. Shake. Add 10 ml water to vial 3. Add a pinch of salt to vial 4 and 10 ml water. Stir. 3. Using the tweezers add each piece of plastic to each vial. Record whether it sinks or floats. Shake the plastic in the vial to remove air bubbles. Dry the plastic on a paper towel in between trials. 4. Rub each plastic with the round end of a paper clip. Record whether a permanent scratch results. (yes, no) 5. Place each piece in the acetone for one minute. Remove from the alcohol and scrape it with your fingernail. Record any observations.
Part II 1. Gently bend your strips back and forth. Record how flexible it is. Record flexibility from 1-6, with 1 being the least, 6 the most. 2. Bend the strip to observe the color of the crease it makes. 3. Get some hot water. Add the pieces, heat them, and pull them out. Record whether they change or not.
Prediction: Which plastic is the unknown? Data:
Part I
plastic number vial 1 2 3 4 Stratches? Reaction to acetone 1 2 3 4 5 6 unknown
Part 2 plastic name flexibility crease color heat Name (from reading) 1 2 3 4 5 6 unknown analysis:
1. Which was the unknown? Why do you think so?
2. Which test was most helpful in its’ identification?
3. Why was that test most helpful?
4. Which plastic was least flexible? Name a product which it would be good to use for. Why? 5. Which plastic would be best for a container of nail polish? Why?
6. Which types would be safe in a dishwasher? Why?
7. If you are a toy designer, why would crease color be important to you?
8. Plastic litter has washed up in oceans all over the world from trash dumping. Why?
9. From the reading selection:
a. Which plastics are safest for food?
b. Which are not safe for food?
c. Which plastics are most likely to be recycled?
d. Which plastics are harmful to the environment?
10. What can you do to reduce plastic trash in oceans and landfills?
Conclusion: 2 things you learned: Know Your Plastic Recycling Number! Published June 14, 2008 Colors / Materials Trends , Environment / Sustainability
Snippet from smartplanet.com article.
1. Polyethylene terephthalate (PET or PETE) Polyethylene terephthalate (PET or PETE) is one of the most common types of plastic and is commonly found in bottles of soda, juice, water and cough syrup and jars of peanut butter. The bottoms of these containers are usually stamped with the chasing arrows symbol and the number 1, the code for PET.
2. High-density polyethylene (HDPE) High-density polyethylene, or No. 2 HDPE, is used in shampoo and detergent bottles, milk jugs, cosmetics, motor oil, toys and sturdy shopping bags, and is considered one of the safer plastics. HDPE is often opaque or cloudy. Some recycling centers can only handle clear No. 2 plastics, such as milk jugs, but not colored bottles. As rule of thumb, bottles, jars, and jugs are most likely to be collected for recycling, particularly those labeled 1 or 2. Tubs, lids, spray pumps, buckets, films, bags and items containing toxic chemicals such as drain cleaner, are less likely to be accepted by recyclers.
3. Polyvinyl chloride (PVC) Polyvinyl chloride, or No. 3 PVC, is found in shower curtains, meat and cheese wrappers, ring binders, some bottles, plumbing pipes and building materials. Commonly called vinyl, PVC and closely related PVDC differ from other vinyls, because they contain toxic chloride. PVC continues to be used in many toys.
4. Low-density polyethylene (LDPE) Low-density polyethylene, or No. 4 LDPE, is used in shopping bags, six-pack rings, hard drive casings, CD and DVD cases and some bottles. Unlike PVC, LDPE isn’t regarded as a ‘bad’ plastic by most eco watchdogs. Potentially toxic industrial chemicals involved in its manufacture, however, include butane, benzene and vinyl acetate.
5. Polypropylene (PP) Polypropylene, or PP, is used in many products including diapers, pails, dishes, candy containers and lab equipment. Some products are made from recycled polypropylene. Makers of electronics packaging, including Microsoft, are increasingly using the recycled PP instead of toxic PVC.
6. Polystyrene, or Styrofoam Polystyrene, also known as Styrofoam, is used in disposable cups and take-out food containers, packing peanuts, trays and egg cartons. Most fast-food chains, including McDonald’s, phased out polystyrene for sandwich containers more than 20 years ago. Ozone layer-depleting CFCs haven’t been used to make Polystyrene since the late 1980s.
7. ‘Wild card’ The No. 7 SPI code is generally a wild card marking plastics that don’t fall within the other six categories. These include polycarbonate bottles, which are understood by scientists to wreak havoc on human hormones by leaching bisphenol-A into hot beverages. As a result, polycarbonate baby bottles are losing favor with the public, and retailers including Toys ‘R Us are starting to sell more BPA-free bottles.
Thanks Smartplanet.com