Year 9 Science · Unit 2 · Lesson 20

Materials Science, Unit Review

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Learning Goals

Link the bonding in a material to the property that makes it useful.
Use real data on a solar panel to follow its materials to the end of its life.
Plan an investigation question and hypothesis for a depth study.

Warm Up

1. Complete the table to compare steel and polyethylene.

Recall 4 marks

Feature	Steel	Polyethylene
Type of bonding
Conducts electricity?
A chemical property
Where the raw material comes from

Your Turn

Data: what is in a solar panel?

A rooftop solar panel is a sandwich of materials. A glass sheet covers silicon cells joined by copper strips. The cells are sealed in a layer of the polymer EVA, which is cross-linked when the panel is made. An aluminium frame holds it all together.

Table 1. Materials in a typical silicon solar panel, by mass

Material	Main job	Share of mass (%)
Glass	front cover	76
Polymers	seal the cells; back sheet	10
Aluminium	frame	8
Silicon	solar cells	5
Copper	wires between cells	1
Silver and other metals	contact lines	less than 0.1

Source: IRENA and IEA-PVPS (2016), End-of-Life Management: Solar Photovoltaic Panels.

2. A worn-out panel has a mass of 20 kg. Use Table 1 to calculate the mass of glass, of aluminium and of polymer in it.

Apply 3 marks

3. For each part of the panel, name the type of bonding or structure and one property that suits its job.

Apply 4 marks

Part	Bonding or structure	Property that suits its job
Aluminium frame
Copper wires
Glass cover (silicon dioxide network)
EVA seal

Go Deeper

4. Recyclers normally remove the aluminium frame first. Using the unit’s ideas about metals and finite resources, suggest two reasons why.

Analyse 2 marks

5. The EVA seal is cross-linked. Use Lesson 17 to explain why this makes it hard to separate the glass, silicon and copper when the panel is recycled.

Analyse 3 marks

Plan a short investigation

Question: “Does the amount of glycerol in a starch bioplastic film affect how far the film stretches before it breaks?” (Glycerol acts as a plasticiser.)

Hypothesis

If … then … because …

Variables

Independent
Dependent
Controlled (2)

Results table headings, with units

Show What You Know

6. Evaluate the statement: “Materials science is just about making things stronger.” Use the solar panel and at least three different parts of the Materials unit.

Analyse 5 marks