Rust: iron's slow fire

Tests: 8 of 11 right · Exam: 0 of 4 right · Kind: plain · Understood: 10 of 15 · Run: 2026-10-18, commit f3c23ea72

Lesson 13 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 ✓

Max reckons rust is just orange dirt stuck on the bike, wash it and it's fine. What's true?

1. Rust is a new substance made from the iron itself — ← Mova's choice · ✓ the right answer · no support
2. He's right, it is just road dust that sticks to the wet metal — no support
3. It is a mould that grows on wet metal — no support
4. It is old paint that has gone orange — 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 · wrong ✗

You keep a nail in a sealed jar with a packet of drying crystals, which soak up any water. What will happen?

1. It will rust even faster than a nail left out in the rain — ← Mova's choice · score 3
2. It will turn green like copper — score 2
3. It will rust only at night — no support
4. It will hardly rust, because there is no water — ✓ the right answer · no support

Why: It took the question to ask what happens next. It chose option 1 with score 3, against 2 for the next best. Its support: lesson 13, line 1: «Leave a bike out in the rain all winter and its chain and bolts turn orange-brown and flaky. That orange stuff is rust, a brand-new substance, not dirt that ha…», reached through the option's own match among the sentences about the question's things. What matched: the same place «rain» (+3); the same action «leave out» (+1). Against it: a different thing acted on (counts against) (-1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 3 · right ✓

"dad says if u scratch the car it'll rust there first. why tho?"

1. The paint turns into rust at a scratch — no support
2. Scratches pull salt out of the air like a magnet — no support
3. The scratch lets air and water reach bare iron — ← Mova's choice · ✓ the right answer · score 5
4. The scratch makes the metal much hotter there — no support

Why: It took the question to ask which statement is true. It chose option 3 with score 5, the only option with support. Its support: lesson 13, line 9: «Salt from sea spray or from gritted winter roads makes iron rust faster, so cars and railings by the sea rust quickly.», reached through the same lesson line as the sentence the question matched. What matched: the same action «make» (+3); the same thing acted on «iron» (+2). · the question and its options parsed, with trees and pragmatics

Test 4 · right ✓

Gran, washing her car after a snowy week: "it's the road salt". Why bother?

1. Salt left on the car speeds up rusting — ← Mova's choice · ✓ the right answer · score 8
2. Salt freezes hard and cracks the windows — no support
3. Salt makes the paint change colour in the sun — score 4
4. Salt makes the car slower on the road — score 4

Why: It took the question to ask which statement is true. It chose option 1 with score 8, against 4 for the next best. Its support: lesson 8, line 4: «Dissolved things are harder: salt in water passes through any filter, so you must let the water evaporate to leave the salt behind, or boil it off and catch th…», reached through the remembered sentence the question matched. What matched: the same action «leave» (+4); the same thing acted on «salt» (+4). · the question and its options parsed, with trees and pragmatics

Test 5 · wrong ✗

Ollie: "my old bike's all rusty so it must be warm, rusting makes heat". What's true?

1. Rusting takes in heat and slowly cools the bike down — no support
2. It makes heat, but far too slowly to feel — ✓ the right answer · score 8
3. He's right, rusty bikes feel warm — ← Mova's choice · score 10
4. Rusting makes no heat at all — score 6

Why: It took the question to ask which statement is true. It chose option 3 with score 10, against 8 for the next best. Its support: lesson 13, line 14: «Rusting gives out heat; hand warmers use iron powder that rusts quickly once the pack is opened, while a rusty bike rusts too slowly to feel warm.», reached through the remembered sentence the question matched. What matched: the same action «feel» (+4); the same doer «rusty bike» (+4); the same property (+2). The right option, 2, scored 8. · the question and its options parsed, with trees and pragmatics

Test 6 · wrong ✗

Mia says the green on the Statue of Liberty means it's falling apart and should be scrubbed off. What's true?

1. The green coat protects the copper under it — ✓ the right answer · no support
2. The statue was always meant to be green paint — ← Mova's choice · score 0
3. Scrubbing would make it green again faster — no support
4. The green is rot that eats the copper away — no support

Why: It took the question to ask which statement is true. It chose option 2 with score 0, the only option with support. Its support: lesson 3, line 19: «A molecule is the same whether a plant or a lab made it, and natural does not always mean safe: the berries of deadly nightshade, a wild plant, are poisonous.», reached through the remembered sentence the question matched. What matched: the same action «mean» (+4); the same property (+2). Against it: one says «not», the other does not (counts against) (-6). The right option, 1, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 7 · right ✓

Leo stepped on a shiny, clean nail in a muddy field. "it's not rusty, so no worries". Right?

1. No, the germ comes from the dirt, so get it checked — ← Mova's choice · ✓ the right answer · no support
2. Yes, only rusty nails are any risk — no support
3. Yes, shiny metal kills any germs as soon as they touch it — no support
4. No, shiny nails are more dangerous than rusty ones — 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

Test 8 · right ✓

If a cartoon robot made of plain iron went swimming in the sea every day, what would happen?

1. It would stay shiny thanks to the salt — no support
2. It would slowly turn into stainless steel — no support
3. It would turn green like a statue — no support
4. It would rust fast, sped up by the salt — ← Mova's choice · ✓ the right answer · score 4

Why: It took the question to ask which statement is true. It chose option 4 with score 4, the only option with support. Its support: lesson 13, line 9: «Salt from sea spray or from gritted winter roads makes iron rust faster, so cars and railings by the sea rust quickly.», reached through the same lesson line as the sentence the question matched. What matched: the same action «rust» (+3); the same property (+1). · the question and its options parsed, with trees and pragmatics

Test 9 · right ✓

Which spoon would you expect to stay shiny for years in a wet kitchen?

1. A stainless-steel spoon — ← Mova's choice · ✓ the right answer · score 6
2. A rough plain iron spoon — score 6
3. A bright copper teaspoon — no support
4. A painted iron spoon, chipped — score 6

Why: It took the question to ask who or what does it. It chose option 1 with score 6, tied with another option at 6 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 11, line 18: «An ordinary metal spoon does not burn in a flame, it only gets hot; very fine steel wool can burn because thin threads have so much surface.», reached through the remembered sentence the question matched. What matched: it fills the role the question asks for (+4); the same doer «spoon» (+2). · the question and its options parsed, with trees and pragmatics

Test 10 · right ✓

"why'd they cover the fence in zinc, it's gonna corrode anyway innit". What's the point?

1. Zinc makes the fence stronger in high wind — no support
2. Zinc is cheaper than painting it — no support
3. Zinc keeps the snails off the fence — no support
4. The zinc corrodes first and saves the steel — ← Mova's choice · ✓ the right answer · score 3

Why: It took the question to ask what it is done to. It chose option 4 with score 3, the only option with support. Its support: lesson 13, line 12: «Galvanised steel is coated with zinc; the zinc reacts first and "sacrifices" itself, so the iron stays safe even at small scratches, and ships carry zinc block…», reached through the remembered sentence the question matched. What matched: it fills the role the question asks for (+4); the same thing acted on «galvanised steel» (+2). Against it: a different action (counts against) (-3). · the question and its options parsed, with trees and pragmatics

Test 11 · right ✓

A space game says Mars is red because it is covered in lava. What's the real reason?

1. Its dust contains iron oxide, like rust — ← Mova's choice · ✓ the right answer · score 9
2. It is covered in red sea water — no support
3. It has red trees and plants — no support
4. It is glowing red-hot all the time — no support

Why: It took the question to ask what it is done to. It chose option 1 with score 9, the only option with support. Its support: lesson 13, line 18: «Mars looks red because its dust contains iron oxide, the same kind of substance as rust.», reached through a sentence linked to the one the question matched. What matched: it fills the role the question asks for (+3); the same action «contain» (+2); the same doer «dust» (+2); the same thing acted on «iron oxide» (+2). · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · wrong ✗

Identify the two substances whose simultaneous presence is required for the rusting of iron.

1. Carbon and sunlight — ← Mova's choice · no support
2. Oxygen and water — ✓ the right answer · no support
3. Oxygen and sea salt — no support
4. Nitrogen and water — 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 2 · formal language · wrong ✗

It is given that a steel article is coated with a layer of zinc. Select the statement most consistent with the established facts concerning such a coating.

1. The zinc reacts preferentially and thereby protects the steel — ✓ the right answer · score 4
2. The zinc converts the steel beneath it into stainless steel — ← Mova's choice · score 6
3. The zinc accelerates the rusting of the steel — no support
4. The zinc renders the steel incapable of conducting heat — no support

Why: It took the question to ask which statement is true. It chose option 2 with score 6, against 4 for the next best. Its support: lesson 13, line 12: «Galvanised steel is coated with zinc; the zinc reacts first and "sacrifices" itself, so the iron stays safe even at small scratches, and ships carry zinc block…», reached through the remembered sentence the question matched. What matched: the same thing acted on «galvanised steel» (+4); the same circumstance (+4). Against it: a different action (counts against) (-2). The right option, 1, scored 4. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · wrong ✗

Which of the following statements most accurately characterises the cause of tetanus?

1. It is caused by contact with iron oxide upon old metal — ← Mova's choice · no support
2. It is caused by a germ present in soil and dirt — ✓ the right answer · no support
3. It is caused by the coldness of metal objects — no support
4. It is caused by the orange pigment of rust — 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 ✗

Ascertain the principal reason for which rusting, once commenced, proceeds into the depth of the metal.

1. The rust dissolves the paint on other surfaces — ← Mova's choice · no support
2. The rust attracts magnets that tear the metal — no support
3. The rust flakes away and exposes fresh iron — ✓ the right answer · no support
4. The rust conducts heat into the metal — 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

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/chemistry/13-rust-irons-slow-fire/