Year 9 Science · Unit 2 · Lesson 17
Challenge Worksheet
Learning Goals
Design a mini-experiment
A materials scientist wants to test: "Does chain length affect the flexibility of a polymer material?"comparing LDPE samples (low-density, branched chains) against HDPE samples (high-density, tightly packed straight chains). Plan the investigation below.
| What I will change (independent variable) | |
| What I will keep the same (controlled variables, list 3) | |
| What I will measure (dependent variable) | |
| My prediction | |
| How I would know if my prediction is wrong (falsification) | |
| One limitation of this experiment |
1. A design engineer needs a polymer for a car dashboard that must: withstand temperatures up to 80 °C without deforming, resist chemical solvents, and maintain rigid dimensional stability over the vehicle's 15-year life. Using your knowledge of thermoplastics and thermosets, identify which type would be more suitable and explain your reasoning across at least three relevant properties. Include at least one named example polymer.
2. A manufacturer claims: "We can recycle thermoset polymers just as easily as thermoplastics, we simply melt them down and remould them into new products." Identify the scientific error in this claim and explain, using your knowledge of polymer structure, why this process is impossible for thermosets. What can be done with end-of-life thermoset materials instead?
Wrap Up
In one sentence, what was the main idea of this lesson?