Plastics

Explain in your own words what a plastic is, where the raw material for most of them comes from (crude oil), and what polymers are: long chains of repeating molecules that give the material its properties.

List three common properties of plastics that explain their huge success (lightweight, insulating, cheap, do not corrode, easy to mould) and name an everyday object that takes advantage of each of the three you choose.

Put in order the journey of crude oil to a plastic bottle and explain what happens at each stage: factory converting plastic pellets into containers, oil extraction, refinery producing chemical raw materials, polymer production in pellet form, shop.

The figure classifies plastics into three families according to their behavior with heat, but one of them is unlabelled.

Observe the behavior and examples of the covered family: name it, explain what distinguishes it from the other two, and add two everyday objects that belong to it.

Define each type of plastic in one sentence — thermoplastic, thermosetting plastic and elastomer —, give an example of an object for each one, and explain which of the three can be remelted and remoulded.

Topic challenge. Classify plastics according to their behavior when heated and their elasticity: thermoplastic (softens with heat and can be molded again), thermoset (does not soften when heated; once molded it stays rigid) and elastomer (very elastic, recovers its shape after being stretched).

Match each object with the type of plastic that fits best:

1. a) Water bottle.

1. b) Frying pan handle, which does not soften when close to fire.

1. c) Rubber band.

1. d) Flexible insulation covering an electric cable.

Then, justify one of your choices and answer: what would happen if the frying pan handle were made of a thermoplastic?

You will be assessed on: correctly assigning the type of plastic to each object, justifying one choice using the properties of the material, and explaining well what would happen with the thermoplastic handle.

Choose the appropriate plastic for each application and justify the choice using a property: (a) a window that imitates glass; (b) a saucepan handle; (c) a flexible garden hose; (d) cling film for wrapping food.

A frying pan handle is made of Bakelite, a thermosetting plastic. Reason why a thermoplastic cannot be used for this purpose, what would happen to polyethylene near heat, and what other kitchen item you think uses the same material for the same reason.

The figure shows several plastic identification symbols with their number, their abbreviation and their common uses, but one is incomplete: its number and abbreviation are missing.

The covered symbol corresponds to the plastic used for pipes and window profiles, a rigid material that is resistant to weathering and contains chlorine in its composition. State its number and its abbreviation, and explain what this identification code is used for when recycling.

The triangle with a number that appears on many packaging items does not mean 'this object will be recycled', but 'this is the material it is made of'. Explain the difference between both ideas and why confusing them leads to incorrect waste disposal.

State whether these statements are true or false and justify each answer: (a) all plastics can be melted and remoulded; (b) plastic is a naturally occurring material; (c) elastomers recover their shape after being stretched; (d) the number inside the recycling triangle ranges from 1 to 7.

The figure shows the lifecycle of a bottle from raw material to waste, with three possible final destinations, one of which is covered.

Of the three possible destinations for the used bottle, the covered one is the only one that turns waste back into raw material. Name it, explain which bin starts that process in Mexico, and what difference exists between that destination and the other two.

Find three plastic containers at home with the triangle symbol and write down their numbers. Research which material each number indicates and order the three from easiest to hardest to recycle in a recycling bin, justifying the order.

Explain what microplastics are, cite two everyday sources that generate them (synthetic clothing in the washing machine, tyre wear or cosmetics with microbeads), and reason how they can end up in the food chain.

Explain what a bioplastic is (plastic obtained from plants such as maize or potatoes), what difference exists between 'plant-based' and 'biodegradable', and why a bioplastic cannot always be thrown into the organic waste bin.

Analyse the plastic paradox: a material that lasts for hundreds of years is used mainly for single-use items lasting minutes (straws, bags, food wrappers). Explain how this situation came about and propose three changes — in design, habits and regulations — to correct it.

A packaging item is advertised as 'green' because it is biodegradable, but the small print clarifies that it only degrades in industrial composting plants. Formulate three questions you should ask yourself before believing the label, and explain what greenwashing is using this example.

A family consumes $12\ \text{L}$ of water per week in $1.5\ \text{L}$ PET bottles (each empty bottle weighs $30\ \text{g}$) and $6\ \text{L}$ of milk in $1\ \text{L}$ PE-HD bottles ($28\ \text{g}$ per bottle). To reduce their environmental impact, they are considering replacing the water bottles with $6\ \text{L}$ PET jugs ($95\ \text{g}$ each) and the milk with $1\ \text{L}$ carton bricks (each carton contains $11\ \text{g}$ of polyethylene, $15\ \text{g}$ of paperboard, and $2\ \text{g}$ of aluminum).

1. a) Calculate the total mass of plastic (in $\text{kg}$) discarded by the family per year ($52\ \text{weeks}$) under their original consumption.
2. b) Calculate how many kilograms of plastic waste they would save per year if they adopt the proposed change.
3. c) Even though the carton brick uses less plastic than the PE-HD bottle, explain why, from the perspective of mechanical recycling and the circular economy, it poses a much greater technological challenge than a monomaterial container.

For the end-of-year party, two options for cups are being considered: disposable PET cups or reusable hard plastic cups. Analyze the cost per use, safety (breakage), waste generated over fifty parties, and washing effort, and recommend an option with supporting arguments.

Design the recycling system for a school festival: which bins you would set up, what types of plastic you expect to find based on what is sold, what problem 'compostable' cups pose if they end up in the plastics recycling bin, and how you would explain this on a poster.

When recycling plastic, the material loses quality with each cycle and ends up in lower-grade products, whereas glass or aluminum can be recycled almost infinitely. Explain what this difference means for the circular economy and what practical consequence it has when choosing packaging.

A cloth bag needs to be used many times to offset its manufacturing environmental impact compared to a plastic bag. Reason which factors determine this 'break-even point' (material, washing, manufacturing distance) and which habit is more important than the choice of bag itself.

You need to choose the material for an outdoor toy casing: compare a rigid thermoplastic such as ABS, flexible polypropylene, and treated wood, assessing resistance to sun and water, impact safety, cost, and end-of-life disposal. Decide on and defend your choice.

Write four rules for the 'responsible use of plastic' in your school technology workshop (purchasing, reusing offcuts, recycling by type, and alternatives) and justify each one by explaining the problem it avoids.