The questions are on the synthetic materials test. Take it under real conditions before reading the mark scheme.
Quick answer: Synthetic materials are substances made by people through chemical reactions, usually from natural resources such as crude oil. This mark scheme gives the model answers and the marks for the 8 questions of the grade 8 science test on synthetic materials, from key words to environmental impact, with the equivalent answers to accept.
Marks are shown in each model answer. Accept any equivalent wording that is scientifically correct, and apply error-carried-forward where a later part uses an earlier wrong value.
Level: Grade 8 science (Year 9 · Class 8) · Curriculum: MS-PS1-3
Question 1 Key words (2 marks)
- A monomer is a small molecule that joins with others to make a polymer.
- Polymerisation.
Marking: 1 mark each.
Question 2 Raw material (2 marks)
- Crude oil.
- A refinery.
Marking: 1 mark each.
Question 3 Density (3 marks)
- ρ = 18.4 ÷ 16.0 = 1.15 g/cm³.
- It sinks, because 1.15 is greater than 1.00.
Marking: 1 mark for the formula and substitution, 1 for 1.15 g/cm³; 1 mark for sinks.
Question 4 Float or sink (2 marks)
- Block Y.
- It sinks, so its density is more than that of water, while X floats because its density is less.
Marking: 1 mark each.
Question 5 Recycling rate (3 marks)
- 160 ÷ 640 × 100 = 25 %.
- 640 − 160 = 480 kg.
Marking: 1 mark for the method, 1 for 25 %; 1 mark for 480 kg.
Question 6 Conservation of mass (2 marks)
- 140 g.
- No atoms are lost or gained, so mass is conserved.
Marking: 1 mark each.
Question 7 Natural versus synthetic (3 marks)
- Synthetic materials can be made with chosen properties, such as being stronger or lighter than wool or silk. They are usually cheaper and can be produced in large amounts, so they do not depend on harvests or animals.
Marking: 1 mark for each reason, 1 mark for a clear link to a property or example.
Question 8 Environmental impact (3 marks)
- Plastics last for centuries and break into microplastics, which spread through water and harm wildlife.
- Sort plastic for recycling, or stop using single-use bottles.
Marking: 1 mark for each problem; 1 mark for a sensible action.
