Year 9 Science · Unit 2 · Lesson 20
Apply Worksheet
Learning Goals
Compare two
Complete the table to compare steel (a metal alloy) and polyethylene (a synthetic polymer) across the unit's framework. Use your knowledge from across the unit, most cells are blank for you to fill in.
| Feature | Steel | Polyethylene |
|---|---|---|
| Bond type | ||
| Physical properties (melting point, conductivity, density) | ||
| Chemical properties (flammability, corrosion resistance) | ||
| Origin (describe the finite resource and extraction/production process) | ||
| Environmental end-of-life (recycling, degradation, pollution) |
Scenario
An engineering team is designing a reusable water bottle for use in the remote Australian outback. The bottle must meet these requirements: hold 1 litre of water at up to 80℃, resist corrosion from sports electrolytes, withstand being dropped on rocky ground, remain stable under prolonged UV exposure in direct sunlight, and be recyclable at the end of its life.
(a) For each engineering requirement below, name the material property (from the unit) that is most relevant.
| Requirement | Relevant material property |
|---|---|
| Hold water at 80℃ | |
| Resist corrosion from electrolytes | |
| Withstand impact from being dropped | |
| UV stability outdoors | |
| Recyclable at end of life |
(b) Recommend whether the bottle body should be made from a metal, a synthetic polymer, or a composite material. Justify your recommendation using at least three material properties from part (a).
1. Crude oil undergoes fractional distillation to separate hydrocarbons by boiling point. Explain, using your knowledge of molecular structure, why shorter-chain alkanes have lower boiling points than longer-chain alkanes.
2. A thermosetting polymer and a thermoplastic polymer are both made from monomers by polymerisation. Explain why a thermoset cannot be melted and remoulded once set, but a thermoplastic can. Link your answer to the unit's bonding concepts.
Wrap Up
In one sentence, what was the most important idea you applied in this worksheet?