Year 9 Science · Unit 2 · Lesson 19
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Learning Goals
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
A piece of plastic 3 mm across is a microplastic.
Correct it:
Photodegradation turns plastic back into carbon dioxide and water.
Correct it:
Biomagnification means a substance becomes more concentrated at each higher level of a food chain.
Correct it:
Rubber worn off car tyres is a source of microplastics.
Correct it:
Microplastics stay in the ocean and have never been found inside the human body.
Correct it:
1. State what bioaccumulation means. Name one sea animal in which microplastics can bioaccumulate, and say how they get into it.
Data: fibres from one load of washing
Researchers at the University of Plymouth washed three synthetic fabrics in a home washing machine at 30 °C and 40 °C. They counted the fibres in the waste water and estimated the number released by a typical 6 kg load.
| Fabric | Fibres per 6 kg wash |
|---|---|
| Polyester–cotton blend | 138 000 |
| Polyester | 496 000 |
| Acrylic | 729 000 |
Source: Napper, I. E. and Thompson, R. C. (2016), Marine Pollution Bulletin 112, pages 39–45. Values rounded to the nearest thousand.
2. A household washes one 6 kg load of acrylic clothes every week. How many fibres could this release in a year of 52 weeks? Give your answer in millions, to the nearest million.
Answer million fibres
3. The household swaps its acrylic clothes for polyester–cotton ones. By what percentage would the fibres per wash fall? Show your working.
Answer %
4. Draw a bar graph of Table 1. Label both axes, with units.
5. The researchers used a 6 kg load for every fabric and tested each one at the same two temperatures. Explain why, and name one other variable they needed to keep the same.
6. Lesson 18 says tyre wear is the largest source of microplastics worldwide. Explain how tyre particles get from a road into the ocean, and give one reason this source is hard to reduce.
Scenario: two policies
A state government wants fewer microfibres in its rivers. Policy A: ban the sale of all clothing made from synthetic fibres. Policy B: require every new washing machine sold in the state to have a filter that catches microfibres.
7. Evaluate which policy would be more practical and effective. Use Table 1, and consider at least two factors besides the number of fibres caught.