---
title: Soap and why washing works — how Mova does on the tests · Chemistry
description: Lesson 24 of the chemistry course of Mova's primary school: 8 of 11 tests right, exam 3 of 4, every question with the options, the student's choice, the right answer and why it chose.
---

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# Soap and why washing works

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**Tests:** 8 of 11 right · **Exam:** 3 of 4 right · **Kind:** ★★ · **Understood:** 8 of 15 · **Run:** 2026-10-18, commit `f3c23ea72`

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Lesson 24 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](https://md.mova.elamur.ai/free/en/corpora/school/chemistry/24-soap-and-why-washing-works/).

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Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: [the lesson's questions in the corpora](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/).

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### Test 1 · ★★ · wrong ✗ {#t1}

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"i just splashed my hands under the tap after the garden, that's fine yeah?" What's true?

- **1.** No, you need to scrub with sand — **← Mova's choice** · no support
- **2.** Soap and about 20 seconds work much better — **✓ the right answer** · no support
- **3.** Yes, if the water is really cold — no support
- **4.** Yes, water alone washes away every single germ — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t1/)

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### Test 2 · ★★ · right ✓ {#t2}

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Mia uses gel on muddy hands and says they're clean now. What's the catch?

- **1.** Gel doesn't remove dirt and works poorly on dirty hands — **← Mova's choice** · **✓ the right answer** · score 11
- **2.** Nothing, gel is better than soap here — no support
- **3.** Gel only works on wet hands — score 6
- **4.** Gel turns mud into soap — no support

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**Why:** It took the question to ask what it is done to. It chose option 1 with score 11, against 6 for the next best. Its support: lesson 24, line 4: «Long ago people made soap by boiling fat with lye from wood ash, a very harsh alkali, so not a kitchen experiment. Today washing powders also carry enzymes tha…», reached through the same lesson line as the sentence the question matched. What matched: it fills the role the question asks for (+5); the same thing acted on «dirt» (+4); the same doer «gel» (+2). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t2/)

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### Test 3 · ★★ · right ✓ {#t3}

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Little cousin is about to put washing-up liquid in the dishwasher "to make it cleaner". What happens?

- **1.** The dishes come out extra clean and shiny — no support
- **2.** Foam overflows out of the machine — **← Mova's choice** · **✓ the right answer** · score 6
- **3.** The machine works twice as fast — no support
- **4.** Nothing happens at all — no support

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**Why:** It took the question to ask what happens next. It chose option 2 with score 6, the only option with support. Its support: lesson 24, line 14: «Dishwasher detergent is made not to foam, so washing-up liquid must never go in a dishwasher: the foam would overflow.», reached through what followed the sentence the question matched. What matched: the same doer «foam» (+5); the same action «overflow» (+1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t3/)

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### Test 4 · ★★ · right ✓ {#t4}

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A cartoon shows a cube-shaped soap bubble floating across the sky. What would a real bubble do?

- **1.** Burst before it can form — score 8
- **2.** Pull itself into a ball — **← Mova's choice** · **✓ the right answer** · score 10
- **3.** Turn into a triangle — score 8
- **4.** Keep its cube shape — score 8

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**Why:** It took the question to ask what is done. It chose option 2 with score 10, against 8 for the next best. Its support: lesson 24, line 3: «Soap weakens the "skin" of water, its surface tension. Sprinkle pepper on water, touch it with a soapy finger, and the pepper races to the edges, pulled by the…», reached through the remembered sentence the question matched. What matched: it fills the role the question asks for (+6); the same action «pull» (+4); the same place «ball» (+4). Against it: a different doer (counts against) (-2); a different thing acted on (counts against) (-2). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t4/)

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### Test 5 · ★★ · wrong ✗ {#t5}

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Josh says lots of foam means the washing-up liquid is working harder. What's true?

- **1.** He's right, foam does the cleaning — **← Mova's choice** · no support
- **2.** Foam is just water and air with no soap — no support
- **3.** More foam makes plates greasier — no support
- **4.** The soap cleans whether there's foam or not — **✓ the right answer** · no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t5/)

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### Test 6 · ★★ · right ✓ {#t6}

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If you put a drop of soap behind a paper boat on a still pond, what would happen?

- **1.** The boat would shoot forward — **← Mova's choice** · **✓ the right answer** · score 1
- **2.** The boat would spin in circles — no support
- **3.** The boat would sink at once — no support
- **4.** Nothing would happen at all — no support

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**Why:** It took the question to ask what happens next. It chose option 1 with score 1, the only option with support. Its support: lesson 24, line 7: «Soap weakens the surface tension of water; the stronger "skin" at the edges pulls pepper away from a soapy finger, and a paper boat with soap at the back zooms…», reached through the option's own match among the sentences about the question's things. What matched: the same doer «paper boat» (+2). Against it: a different action (counts against) (-1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t6/)

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### Test 7 · ★★ · wrong ✗ {#t7}

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"my bubbles keep popping straight away". What could help?

- **1.** Blow much, much harder and faster — **← Mova's choice** · no support
- **2.** Add a spoon of salt — no support
- **3.** Add a little glycerine or sugar — **✓ the right answer** · no support
- **4.** Use only plain cold tap water — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t7/)

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### Test 8 · ★★ · right ✓ {#t8}

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Grandma's new town makes grey scum in the bath and crusty kettles. What's going on?

- **1.** The water is hard, full of minerals — **← Mova's choice** · **✓ the right answer** · no support
- **2.** The pipes are full of old soap from before — no support
- **3.** The water is too soft — no support
- **4.** Someone put salt in the water tank — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t8/)

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### Test 9 · ★★ · right ✓ {#t9}

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"ugh old-timey soap from wood ash, let's make some in the kitchen!" What's the honest reply?

- **1.** Sure, it's just warm water and ash — score 3
- **2.** Yes, but only in a plastic bowl — no support
- **3.** No, lye is very caustic, not for kids — **← Mova's choice** · **✓ the right answer** · score 4
- **4.** Sure, if you add lemon juice — no support

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**Why:** It took the question to ask which statement is true. It chose option 3 with score 4, against 3 for the next best. Its support: lesson 24, line 11: «In history, soap was made by boiling fat with lye from wood ash; the alkali breaks fats into soap, and lye is very caustic.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «lye» (+2); the same property (+1); the same light verb (be, have, do, get, go) (+1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t9/)

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### Test 10 · ★★ · right ✓ {#t10}

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Why can washing powder get an egg stain out even at 30 °C?

- **1.** Its enzymes break down the stain — **← Mova's choice** · **✓ the right answer** · score 6
- **2.** The stain fades in the dark drum — no support
- **3.** The egg dissolves in any water — no support
- **4.** The machine boils the water anyway — no support

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**Why:** It took the question to ask why something happens (its cause). It chose option 1 with score 6, the only option with support. Its support: lesson 24, line 12: «Washing powder contains detergents and enzymes that break down protein and fat stains, so many modern powders work well at 30 °C and save energy.», reached through the same lesson line as the sentence the question matched. What matched: the same action «break down» (+2); the same doer «detergents» (+2); the same thing acted on «protein» (+2). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t10/)

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### Test 11 · ★★ · right ✓ {#t11}

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Hand gel left by the birthday candles. What's the problem?

- **1.** It is flammable — **← Mova's choice** · **✓ the right answer** · no support
- **2.** It will melt into soap — no support
- **3.** It turns the cake sour — no support
- **4.** Nothing, it's only water — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/t11/)

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### Exam question 1 · formal language · wrong ✗ {#e1}

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Identify the feature of the soap particle by virtue of which it removes grease.

- **1.** It is entirely composed of water — **← Mova's choice** · no support
- **2.** It dissolves grease by the application of considerable heat to the surface — no support
- **3.** It possesses a water-attracting head and a grease-attracting tail — **✓ the right answer** · no support
- **4.** It converts grease directly into gas — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/e1/)

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### Exam question 2 · formal language · right ✓ {#e2}

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It is given that a free soap bubble invariably assumes a spherical form. Ascertain the principal reason.

- **1.** The mixture is spherical within its container — no support
- **2.** A sphere encloses the air with the smallest surface — **← Mova's choice** · **✓ the right answer** · score 5
- **3.** The wind removes the corners of other shapes — no support
- **4.** The air within is heavier at the centre — no support

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**Why:** It took the question to ask which statement is true. It chose option 2 with score 5, the only option with support. Its support: lesson 24, line 9: «A free bubble always becomes a sphere, because a sphere holds the air inside with the smallest surface; even square wire frames make round bubbles.», reached through a sentence linked to the one the question matched. What matched: the same doer «sphere» (+2); the same thing acted on «air» (+2); the same circumstance (+2). Against it: a different action (counts against) (-1). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/e2/)

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### Exam question 3 · formal language · right ✓ {#e3}

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Which of the following statements most accurately characterises alcohol hand gel?

- **1.** It kills many germs but does not remove dirt, and it is flammable — **← Mova's choice** · **✓ the right answer** · score 9
- **2.** It functions best upon visibly dirty hands — score 9
- **3.** It removes dirt more effectively than soap and water — score 6
- **4.** It is safe to swallow in small quantities — no support

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**Why:** It took the question to ask who or what does it. 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 24, line 15: «Alcohol hand gel kills many germs by damaging their outer coat, but it does not remove dirt, works poorly on dirty hands, is flammable and must not be swallowe…», reached through the option's own match among the sentences about the question's things. What matched: it fills the role the question asks for (+3); the same action «kill» (+2); the same doer «hand gel» (+2); the same thing acted on «many germs» (+2). · [the question and its options parsed, with trees and pragmatics](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/e3/)

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### Exam question 4 · formal language · right ✓ {#e4}

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Select the response consistent with the established facts concerning foam in washing-up.

- **1.** Cleaning is performed by the soap particles irrespective of foam — **← Mova's choice** · **✓ the right answer** · no support
- **2.** The greater the foam, the cleaner the dishes, invariably — no support
- **3.** Foam is required for any cleaning whatsoever — no support
- **4.** Cleaning is performed exclusively by the foam — no support

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**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](https://md.mova.elamur.ai/free/en/corpora/questions/chemistry/24-soap-and-why-washing-works/e4/)

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<!-- pn -->
- ← previous: [23. Browning apples, rotting and mould](https://md.mova.elamur.ai/free/en/school-run/chemistry/23-browning-apples-rotting-and-mould/)
- next →: [25. Cleaning chemicals and safety at home](https://md.mova.elamur.ai/free/en/school-run/chemistry/25-cleaning-chemicals-safety/)
- ↑ back to [Chemistry](https://md.mova.elamur.ai/free/en/school-run/chemistry/)