Learning target: I can use qualitative evidence about where a synthetic material comes from, what it does at the end of its life and where a town's waste actually goes to argue whether switching materials would help, and I can spot a claim that the evidence does not support.
Read the scenario, the audit data, the reference table, the town facts and the vendor's flyer. Answer the warm-up questions first; they will organize your evidence. Then write your Claim, Evidence and Reasoning. Your claim can be yes, no, or yes-with-conditions, but it must follow from the evidence, and your reasoning must explain why 'biodegradable' depends on where the cups actually go. Give both materials a fair hearing: each has a real benefit and a real cost.
You will need: This worksheet, Pencil, Scrap paper for the three arrows, Calculator (optional)
Every July the town of Cedar Hollow holds a three-day music festival on the fairgrounds. Last year the food booths handed out about 12,000 drinks in clear PET plastic cups. A town council member has proposed a rule for this year: all booths must switch to PLA cups made from corn, because 'they are biodegradable and PET is not.' A cup supplier has sent the council a flyer. Before the vote, the council asked the high school science club to review the evidence and write a recommendation. The club collected the audit from last year's cleanup crew and looked up what the two materials actually do.
| Where the cups were found | Number of cups | What happened to them next |
|---|---|---|
| Recycling bins | 4100 | Sent to the county sorting plant; about 1 in 5 rejected for food contamination |
| Trash bins | 7300 | Sent to the county landfill, 20 km away |
| On the ground or in the creek | 600 | Picked up by volunteers and sent to the landfill |
| PET cup | PLA cup | |
|---|---|---|
| Natural resource it comes from | petroleum (nonrenewable; drilling and refining can pollute) | corn starch (renewable crop; growing it uses farmland, water and fertilizer) |
| How it is made | petroleum-derived molecules are reacted and joined into long PET chains | glucose from corn starch is fermented to lactic acid, which is joined into long PLA chains |
| In an industrial composter (about 58 °C, moist, aerated) | does not break down | breaks down over weeks to months; the common standard is 90 percent within 180 days |
| In a landfill, a backyard pile, a creek or on the ground | lasts for decades or longer | lasts for years; no useful breakdown |
| In the recycling stream | recyclable where accepted; sorted and melted into new products | not recyclable with PET; looks like PET, and even a small amount can spoil a melted batch of PET |
Before writing, draw three arrows on scrap paper, one for each place a cup can land (recycling bin, trash bin, ground). At the end of each arrow write where that cup goes in Cedar Hollow and what the reference table says PET and PLA do there. The arrow that catches the most cups (use the audit numbers) is the one your reasoning should spend the most words on. Sentence frame for the claim: 'The festival should ______ because, in Cedar Hollow, most cups end up ______, where PLA ______.'
The council also received a proposal for a deposit system: festival-goers pay $2 for a sturdy reusable polypropylene cup, refill it all weekend and get the $2 back when they return it, after which the cups are washed in town and stored for next year. Using W5's break-even idea (a reusable plastic cup takes roughly 30 times the energy of a single-use cup to make), write a second CER on whether this option beats both PET and PLA for Cedar Hollow. Name the two pieces of evidence you would need that this sheet does not give you, such as the return rate and the number of years the cups would last.