Plastics: useful and stubborn

Tests: 8 of 10 right · Exam: 2 of 4 right · Kind: plain · Understood: 9 of 14 · Run: 2026-10-18, commit f3c23ea72

Lesson 29 of the chemistry course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: the lesson in the corpora.

Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: the lesson's questions in the corpora.

Test 1 · right ✓

Kai: "chuck the corn plastic cup on the compost heap in the garden, it'll rot". What's true?

1. Most need a special hot composter — ← Mova's choice · ✓ the right answer · no support
2. It rots in a week on any heap — no support
3. It turns into corn on the heap — no support
4. It is no different from a carrot peel — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 2 · right ✓

"plastic's evil, ban all of it, even in hospitals". What would happen without plastic in hospitals?

1. Keeping tools germ-free would be much harder — ← Mova's choice · ✓ the right answer · score 3
2. Nothing at all would change — no support
3. Doctors would just quietly use plastic anyway — no support
4. Medicine would work much better without it — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 3, the only option with support. Its support: lesson 29, line 16: «In hospitals, sealed plastic syringes, gloves and tubes keep medicine and tools free of germs and are used only once.», reached through the option's own match among the sentences about the question's things. What matched: the same thing acted on «medicine» (+2); the same action «keep» (+1). · the question and its options parsed, with trees and pragmatics

Test 3 · right ✓

If you stretch a rubber band and let go, and then do the same with a plastic bag strip, what's different?

1. The band springs back, the bag stays stretched — ← Mova's choice · ✓ the right answer · score 7
2. Both spring back the same way — no support
3. Both stay stretched the same way — no support
4. The bag springs back, the band stays long — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 7, the only option with support. Its support: lesson 29, line 2: «Long chains make plastics bendy, tough and light. Pull a plastic bag slowly and it thins and stretches before it tears, because the chains slide past each othe…», reached through the remembered sentence the question matched. What matched: the same action «stretch» (+4); the same doer «bag» (+3). · the question and its options parsed, with trees and pragmatics

Test 4 · right ✓

A cartoon says plastic in the sea just melts away in the salty water. What's true?

1. Salt turns plastic into sand — no support
2. Fish eat it all up safely — no support
3. It breaks into tiny bits that last for years — ← Mova's choice · ✓ the right answer · score 2
4. It melts away within a few days in warm sea water — no support

Why: It took the question to ask which statement is true. It chose option 3 with score 2, the only option with support. Its support: lesson 29, line 12: «Many plastics soften when heated, because heat lets the chains move; burning plastic gives off poisonous fumes.», reached through the option's own match among the sentences about the question's things. What matched: the same action «soften» (+1); the same doer «many plastics» (+1). · the question and its options parsed, with trees and pragmatics

Test 5 · right ✓

Dad holds up a bottle: "number 1 in the triangle means it's been recycled once". Right?

1. Yes, it counts how many times it was recycled — score 3
2. Yes, and number 7 means seven times — no support
3. No, it says how many litres it holds — score 6
4. No, the number says which kind of plastic it is — ← Mova's choice · ✓ the right answer · score 7

Why: It took the question to ask which statement is true. It chose option 4 with score 7, against 6 for the next best. Its support: lesson 29, line 8: «The number inside a little triangle of arrows on a plastic item tells which kind of plastic it is; it helps sorting, but not every kind is recycled everywhere.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «number» (+2); the same thing acted on «kind» (+2); the same circumstance (+2); the same light verb (be, have, do, get, go) (+1). · the question and its options parsed, with trees and pragmatics

Test 6 · right ✓

Your mate wants to burn plastic rubbish on the bonfire "to get rid of it". Why not?

1. It gives off poisonous fumes — ← Mova's choice · ✓ the right answer · score 6
2. It makes the whole bonfire go out — no support
3. It makes the fire too cold — no support
4. It is a waste of good fuel — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 6, the only option with support. Its support: lesson 29, line 12: «Many plastics soften when heated, because heat lets the chains move; burning plastic gives off poisonous fumes.», reached through the same lesson line as the sentence the question matched. What matched: the same action «give off» (+4); the same thing acted on «poisonous fumes» (+2). · the question and its options parsed, with trees and pragmatics

Test 7 · wrong ✗

Mia says plastic is made from melted sand. What's true?

1. Plastic is made from melted metal — ← Mova's choice · score 9
2. Plastic is made from tree bark — score 9
3. She's right, sand melts into plastic — score -1
4. Most plastic comes from oil and gas — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 1 with score 9, tied with another option at 9 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 29, line 1: «Look round your kitchen: a water bottle, a lunchbox, a toy brick, the handle of a toothbrush. They feel different, but all are plastics, made of very long chai…», reached through the remembered sentence the question matched. What matched: the same thing acted on «plastics» (+5); the same action «make» (+4). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 8 · right ✓

Why did people queue for hours for nylon stockings when they first came out?

1. Nylon was a cheap, strong new silk replacement — ← Mova's choice · ✓ the right answer · no support
2. Nylon stockings were free on the first day — no support
3. Nylon was only sold to kings — no support
4. Nylon made people warmer than wool — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 9 · right ✓

"the pan's coating is so slippery, how come?"

1. It is magnetic and pushes food away — no support
2. It is a plastic that food cannot grip — ← Mova's choice · ✓ the right answer · score 10
3. It is covered in a thin coat of oil — no support
4. It is made of ice that never melts — no support

Why: It took the question to ask which statement is true. It chose option 2 with score 10, the only option with support. Its support: lesson 29, line 13: «The non-stick coating on frying pans is a slippery plastic that food cannot grip; it was discovered by accident in 1938.», reached through the remembered sentence the question matched. What matched: the same thing acted on «slippery plastic» (+5); the same doer «non-stick coating» (+3); the same light verb (be, have, do, get, go) (+2). · the question and its options parsed, with trees and pragmatics

Test 10 · wrong ✗

If a plastic lunchbox is left on a hot car dashboard all day, what might happen?

1. It may soften and bend out of shape — ✓ the right answer · no support
2. It will start to rot like fruit — no support
3. It will turn into glass — ← Mova's choice · score 1
4. It will get stronger and harder — no support

Why: It took the question to ask what happens next. It chose option 3 with score 1, the only option with support. Its support: lesson 25, line 3: «Some cleaners must never meet: bleach poured together with an acid toilet cleaner gives off chlorine, a poisonous gas. The safe rule is simple: never mix clean…», reached through what followed the sentence the question matched. What matched: the same action «grow» (+1). The right option, 1, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · wrong ✗

Which of the following statements most accurately characterises the molecular structure of plastics?

1. They consist of crystals of sand fused by heat — ← Mova's choice · no support
2. They consist of very long chain molecules termed polymers — ✓ the right answer · no support
3. They consist of individual atoms of a single metal — no support
4. They consist of small spherical molecules of water — no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · right ✓

Identify the principal reason for which plastic debris persists in the marine environment for prolonged periods.

1. Few microorganisms are capable of decomposing it — ← Mova's choice · ✓ the right answer · no support
2. Salt water converts it into stone — no support
3. It is replenished continually by marine animals of many kinds — no support
4. It is dissolved and redeposited each night — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · right ✓

It is given that a numeral is printed within a triangle of arrows upon a plastic container. Ascertain the significance of the said numeral.

1. It identifies the type of plastic — ← Mova's choice · ✓ the right answer · no support
2. It states the capacity in litres — no support
3. It denotes the number of previous recyclings — no support
4. It specifies the year of manufacture — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 4 · formal language · wrong ✗

Select the response that is consistent with the established facts concerning the combustion of plastics.

1. The process is entirely free of hazard — no support
2. The plastic is converted into oil — ← Mova's choice · score 3
3. Only pure water vapour is produced — no support
4. Poisonous fumes are liberated — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 2 with score 3, the only option with support. Its support: lesson 29, line 6: «Most plastics are made from oil and natural gas.», reached through the option's own match among the sentences about the question's things. What matched: the same thing acted on «most plastics» (+2); the same place «oil» (+2). Against it: a different action (counts against) (-1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/chemistry/29-plastics-useful-stubborn/