Skill: course-build → write-mcqs → write-explanation, design-check-sequence @ b0fa825
Topic 13 — How to tell materials apart — the PP100's ten question types, with their exemplars (v2, 2 October 2026)
What this page is. James reads a bank as its question TYPES first (vault: A bank is reviewed as its question types first, one exemplar each). Under the Grade 4 standing brief the bank is built straight away (51 items in content/G4T13_pp100_bank.py: 48 four-option MCQs, 2 typed, 1 multi-select; 16 / 18 / 17 per atom; 16 easy, 21 medium, 14 hard); this sheet is the way in. v2 applies the blind read, the guidance review and the figure review of 2 October: two items cut (the stone-and-pebble card, which repeated L01's attached question; the which-test-first item, which repeated L03-q8), two added (a clay sheet; the one sample left after both tests), nine re-materialled, five reason items rewritten so the stem states the outcome and asks why, one multi-select made a single MCQ, and the ⟂ list added. Each type line says what the stem asks, what the four options (or the accept list) are, and prints one exemplar in full. Tags follow depth of reasoning — easy = one-step predict or sort; medium = the rule applied to a fresh case, the reason picked, or a two-column table read; hard = two ideas chained, a judgement about the routine, a set answer, or a coined term recalled — and rise with the atom's order: MAT4-001 carries easy and medium only; MAT4-003, the capstone, carries medium and hard only. Every hard item carries a one-line "hard because" (hb) in the bank file.
Rulings already applied. Four options on every MCQ (two fixed sets: the predictions "It sinks. / It floats. / It floats, then sinks. / It may do either." and the sort "a floater / a sinker / a floater and a sinker / neither a floater nor a sinker"); no option bundles a verdict with its reason; a reason item states the outcome and asks why ("A tiny steel nut sinks in water. Why does the nut sink?"), never "X is wrong to say…" (review, 2 Oct); every distractor is a reason a child really gives (heavy things sink; a hole lets water in; flat things float; glass is harder), never an absurd one; no key is the one long option; every stem is a positive question; a comparison of two masses is drawn (Grade 3 Topic 18's pan balance) with both blocks in one neutral fill so no colour tracks the key, and an item figure carries no verdict chip or tint; every two-property item reads a drawn table whose cells are yes / no only; "dense" is recognised among sister property words and never typed (James: named once as the label for heavy-for-its-size), and the dense items first state "So X is heavy for its size" so exactly one option is true; the two typed keys are the coined labels floater and sinker; one multi-select, where the answer is genuinely a set (two samples match); every item names ONE atom; US spelling; units as words; a stem of three or more sentences is tagged hard.
The bar list (real things a generated item must never use): any PLASTIC (plastics differ — some float, some sink — and the course has not sorted them); any HOLLOW object (a cup, a can, a bottle, a boat, a toy car, a pole, a pipe, a tube: the air inside is the simplification L02 leaves for a later grade — a bamboo "pole" became a chopstick and a copper "pipe" a rod on the review's science rows); iron filings, pins laid flat, foil (a tiny flat piece can rest on the water's surface film — surface tension is grades 6-8; the iron table reads a bar); foods other than the ones Grade 3 Topic 19 drew (an apple floats; a potato, a grape and a coin sink; an orange and a leaf float); ice, soap, pumice; rubber (balls and bands float, filled erasers sink); a stainless-steel spoon or fork under a MAGNET (many are not magnetic — cutlery is a sink-or-float object only; the magnet items use plain steel: a nail, a bolt, a paperclip, a washer, a pin, a hook, a key, a nut, a button); "copper" for a coin (a penny is not copper); eraser as a floater. No item needs a number for density, a reading, or any arithmetic beyond one subtraction of counts (type 9's "6 − 4 = 2").
The ten types
| Type | Items | Atom | Tags | Form | The stem asks… | The options / the accept | Exemplar scene |
|---|---|---|---|---|---|---|---|
| 1 | 9 | MAT4-001 | easy | MCQ, fixed set | one piece of a material sinks or floats: what does a bigger or smaller piece of the same material do | It sinks. / It floats. / It floats, then sinks. / It may do either. | a gray rock and a chip of it; a maple board and a strip; an apple and a slice; a cedar shaving and a log; a grape cut in half |
| 2 | 1 | MAT4-001 | easy | MCQ on a drawn BEFORE pair | the known piece rests in its tub, the new piece is held above the second tub: what will it do | the same fixed set | a slate roof tile sunk, a slate chip held above |
| 3 | 6 | MAT4-001 | medium | MCQ | which other object is sure to sink; why a tiny steel nut sinks; a new shape of the same wax or clay; what a chip tells you about the block | four objects / four single-statement reasons / the fixed set | a steel washer among a ruler, a cork and a candle; wax rolled into a ball; clay pressed flat |
| 4 | 6 | MAT4-002 | easy | MCQ, fixed set; two drawn as results tables | three pieces of one material all float (or all sink): what is the material | a floater / a sinker / a floater and a sinker / neither a floater nor a sinker | bamboo: a chopstick, a stick, a shaving (drawn); iron: a horseshoe, a nail, a bar (drawn); walnut; brick; birch; aluminum |
| 5 | 3 | MAT4-002 | medium | MCQ | a material is a floater (or sinker): what does an untested piece do; which of four objects sinks | the prediction set / four objects | an untested cedar post; a copper bead; a steel ruler among cork, pine and wood |
| 6 | 2 | MAT4-002 | medium | MCQ; one drawn balance | two blocks of the same size, one pan lower (or one with more mass): which material is heavy (or light) for its size | block C / block D / both / neither; the stone / the cork / both / neither | blocks C and D on the pan balance (drawn, right pan lower, one neutral fill) |
| 7 | 3 | MAT4-002 | medium, hard | MCQ | why a wooden bead and a glass bead of one shape do different things; why a thick pine board floats though it has more mass than a glass bead; a material heavier for its size than water — what does a chip of it do | four single-statement reasons / the prediction set | two beads of one shape; a pine board and a glass bead; a chip of a dense material |
| 8 | 6 | MAT4-003 | medium, hard | MCQ on a drawn two-property table; one with "none" | which one sample matches both named properties; how many match when no row does | the four samples (no material word where it would hand the key over) / none, one, two, all | a desk, a campsite, a craft box (floats + smooth), a drawer (sinks + not pulled), a pond (read the other way) |
| 9 | 10 | MAT4-003 | medium, hard | MCQ | the routine's steps and judgements: what is crossed out first; what comes next; what one passed test tells you; what one sample left after both tests tells you; why the second test cannot be skipped; does the order change the match; two left means two matches; why a failed sample cannot match; how many get the magnet test; testing crossed-out samples finds the same one | four single statements or four counts | a tray of six with four floaters; two children testing in opposite orders |
| 10 | 5 | MAT4-002 / 003 | hard | typed text ×2; MCQ keyed on the term; one MCQ on a dense material; one multi | the coined label from its meaning (typed); the word for heavy for its size (chosen); the statement true of a material more dense than water; the TWO samples that match both | sinker · floater (typed, accept lists with article, plural and child spellings); magnetic / strong / smooth / dense; four statements; a set of two samples (the shed) | "Cork, wax and wood share one name…"; a glass marble against a cork ball of one size |
Hard because — type 7 (the chip of a dense material): heavy-for-its-size against water is read as dense, then dense is carried to every piece. Type 8 (the pond): floats is read as a no under Sinks? and not pulled as a no under Magnet pulls it?; (none match): the routine ends with no sample, not the nearest one. Type 9 (hard tier): each is a judgement about the routine — skipping the second test, the order of the tests, two left after both tests, a failed sample, the count tested with the magnet, extra tests on crossed-out samples. Type 10: a term recalled from its meaning; a dense material's every piece sinks (two ideas chained); the shed leaves TWO samples and both must be chosen.
One exemplar per type, in full
Type 1 (easy, MAT4-001). A big gray rock sinks in a river. What does a small chip of the same rock do in the river? — It sinks. / It floats. / It floats, then sinks. / It may do either. Why: Every piece of one material floats or sinks the same way, whatever its size or shape. The chip is the same rock as the big rock. The big rock sinks, so the chip sinks. (nearest lesson-side instance: L01-q6, the brick and its chip; a different material and setting)
Type 2 (easy, MAT4-001, drawn). The roof tile and the chip are both slate. What will the chip do when Emery lets go of it? — It floats. / It may do either. / It floats, then sinks. / It sinks. (figure pp_slate_before: the slate tile rests on the floor of the left tub, the slate chip is held above the right tub, both the same dark grey; nearest: L01-q6, the brick and its chip, drawn — a different material, the same drawn form: draw one per test)
Type 3 (medium, MAT4-001). A tiny steel nut sinks in water. Why does the nut sink? — The nut is heavy, and heavy things sink. / The nut has a hole, so water gets in. / The nut is steel, and every piece of steel sinks. / The nut is small, and small things sink. Why: Every piece of one material floats or sinks the same way, whatever its size or shape. The nut is steel, and steel sinks. So the nut sinks because it is steel, not because of its size. (nearest: L01-q8, the washer claim, bare yes / no — here the reason is the target; the three distractors are the beliefs children give: weight, a hole, size)
Type 4 (easy, MAT4-002, drawn). Here are the results for three pieces of bamboo. What is bamboo? — a floater / a sinker / a floater and a sinker / neither a floater nor a sinker. (figure pp_results_bamboo: chopstick floats, stick floats, shaving floats; nearest: L02-q4, oak's results table — a different material, the same drawn form)
Type 5 (medium, MAT4-002). Four objects are lowered into water. Which one sinks? — a cork coaster / a pine board / a wooden ruler / a steel ruler. Why: Floating or sinking is a property of the material. Cork, pine and wood are floaters, so the coaster, the board and the wooden ruler float. Steel is a sinker, so the steel ruler sinks. (nearest: none on the lesson side — the odd-one-out form is the bank's)
Type 6 (medium, MAT4-002, drawn). Block C and block D are exactly the same size. Which block is made of a material that is heavy for its size? — both blocks / block C / neither block / block D. (figure pp_balance_blocks, the right pan lower, both blocks one neutral fill, no chips; nearest: L02-q1, the Grade 3 recall on blocks A and B — that item asks only which has more mass)
Type 7 (hard, MAT4-002). A block of a material is heavier for its size than water. What does a small chip of the same material do in water? — It floats. / It sinks. / It may do either. / It floats, then sinks. Hard because: two ideas chained — heavier for its size than water means more dense than water (L02's bridge line: "Steel is heavier for its size than water, so steel sinks"), and being dense is a property of the material, so the chip sinks too. (nearest: L02-q9, the TRUE claim that a steel chip is heavy for its size like a steel bar)
Type 8 (medium, MAT4-003, drawn). Emilia wants the one sample from the craft box that floats and that is smooth. Which sample matches both properties? — the pine cone / the wooden button / the steel button / the pebble. (figure pp_two_craft: Floats? / Smooth?; nearest: L03-q5, the kitchen table with floats + soft — a different second property and a fresh set of samples)
Type 9 (hard, MAT4-003). Elliott's tray has six samples, and four of them float. He wants the sample that sinks and that a magnet pulls. How many samples does he test with the magnet? — 6 / 4 / 0 / 2. Why: Test the first property and cross out every sample that fails it. Four samples float, so four are crossed out, and 6 − 4 = 2 samples are left. The second test is done on the samples left. So Elliott tests 2 samples with the magnet. (nearest: L03-q9, "what does he do next" — here the step is applied to a count)
Type 10 (hard, MAT4-002, typed). Cork, wax and wood share one name, because every piece of each floats. Type that name. (Its twin: "Iron, glass and brick share one name, because every piece of each sinks." → sinker.) — accept: floater, a floater, the floater, floaters, flooter, floter, floatter; a typed "sinker" gets its own line ("A sinker is a material whose every piece sinks. A material whose every piece floats is called a floater."). The chosen-term twin: "A glass marble has much more mass than a cork ball of exactly the same size. So glass is heavy for its size. Which word means heavy for its size?" — magnetic / strong / smooth / dense. (nearest: L02-q12, the definition stem "A material whose every piece floats … Type the name." — the bank's stem is re-instanced as the three materials sharing a name)
⟂ — never drawn into one test together (the blind read's give-aways and the review's list; v2 positions)
- PP-38, PP-39 (the typed terms) ⟂ every item whose option set prints the word: PP-11..16 (type 4), PP-23..25 (type 5), PP-42.
- PP-42 ⟂ PP-38, PP-41 (a dense material's every piece sinks; the chip chain).
- PP-46 ⟂ PP-51 (the order; the extra tests on crossed-out samples — both say the same one sample is found).
- PP-48 ⟂ PP-36, PP-51 (a failed sample cannot match; passed the first test only; the extra tests).
- PP-45 ⟂ PP-35 (the second test on the samples left; skipping it).
- PP-34 ⟂ PP-49 (cross out the floaters; the count tested with the magnet).
- PP-22 ⟂ PP-01..10 (PP-22 states the rule the type-1 and type-2 items test).
- PP-37 ⟂ PP-47 (one left after both tests; two left after both tests).
- PP-06 ⟂ PP-23 (cedar twice: the shaving and the log; the untested post). PP-20 ⟂ PP-07 (clay twice: the sheet; the bead and the block).
- Lesson-side pairs the coordinator's test draw honours: PP-30 ⟂ PR-9 (the lunch box and the desk: a key and a pin); PP-33 ⟂ L03-q2 (the drawer and the pencil case); PP-12 ⟂ PR-6 (iron); PP-23 ⟂ L02-q5 (cedar); PP-20 ⟂ PR-5 (clay). The pine board and strip left the bank (PP-02 is maple) so SUMMARY-Q2 needs no pair.
Design-move inventory (one line per type; move · scene kind · nearest earlier item)
The bank's 51 moves against the lesson side (L01 10 quiz items, L02 12, L03 10, 3 attached, 3 summary, 14 practice):
- Types 1–2 (10 items): predict the other piece of one material — rock/chip, maple board/strip, slate tile/chip (drawn), apple/slice, bead/block of glass, cedar shaving/log, clay bead/block, cork cut in four, grape in half, beeswax slab/sheet. Nearest: L01-q2 (glass marble/bead, drawn), q3 (oak log/twig), q5 (nail/screw), q6 (brick/chip), q7 (potato/slice), SUMMARY-Q1 (glass paperweight/piece), PR-4 (oak block/chip), PR-5 (horseshoe/nail), L01-V (stone/pebble in a pond). Same move by design (the fluency form); every material differs from its nearest (the review's nine renamed templates — steel nail/screw, stone/pebble, candle wax, brick in half, pine — are gone: slate, apple, grape, maple; the stone card was cut).
- Type 3 (6): pick the object sure to sink (washer among ruler, cork, candle); why the light nut sinks (L01-q8's washer claim is yes/no — the reason form is new; the outcome is stated, the stem asks why); a new shape of the same wax and the same clay pressed flat (L01-q9 is the wooden board/cube claim — the materials and the form differ; the clay sheet is the shape belief on a sinker); chip → block (L01-q10 is big → small; here the direction is reversed); two pieces, one sinks (bare rule, no material named).
- Type 4 (6): classify from results — bamboo (drawn), iron (drawn), walnut, brick, birch, aluminum. Nearest: L02-q2 chalk (drawn), q3 copper, q4 oak (drawn), q5 cedar, PR-6 clay, SUMMARY-Q2 pine, L02-V stone. No material is shared with a lesson-side classify item (beeswax and cork, which repeated L01's wax and L02-q6's cork, became walnut and birch — birch, not the reviewer's second maple, so one wood is not in the bank twice).
- Type 5 (3): untested piece of a known floater/sinker — a cedar post, a copper bead (the pine board, SUMMARY-Q2's material, folded into this form as cedar; ⟂ L02-q5). Odd one out — new form.
- Type 6 (2): same-size blocks → heavy or light for its size — blocks C/D drawn (nearest L02-q1 blocks A/B, which asks mass only; PR-7 glass/cork blocks); stone/cork in words asking LIGHT for its size.
- Type 7 (3): the reason — a wooden bead and a glass bead of one shape (nearest: L02's two spoons; the distractors are property confusions a child holds — harder, smoother, see-through — the "air inside the wood" half-truth is gone); a thick pine board heavier than a glass bead (nearest L02-q8, the log claim yes/no; distractors: flat things float, big things float, smoother); the dense chip chain (nearest L02-q9).
- Type 8 (6): two-property table pick — desk, campsite, craft box (floats + smooth), drawer (sinks + not pulled), pond (read the other way), none-match in words. Nearest: L03-q4 garden, q5 kitchen (floats + soft), q6 beach, q7 toy box (none), PR-9 lunch box. Every table is a fresh set of samples (the bathroom table, which carried three of the tray's samples, is the craft box now); the toy-box and the "none" bank item share the outcome with different forms (table vs words) — draw-one-per-test.
- Type 9 (10): routine steps and judgements — what is crossed out, what comes next, one passed test, one left after both tests (new), skip the second test, order of tests, two left, a failed sample, the count tested, extra tests. Nearest: L03-q8 (which first), q9 (what next), q10 (one passed test, the TRUE claim), PR-10 (pebble). The which-test-first bank item (L03-q8's form) was cut; the hard tier's judgements appear nowhere on the lesson side.
- Type 10 (5): term recall — sinker typed (nearest PR-14, stone typed: re-instanced as iron, glass and brick sharing a name), floater typed (nearest L02-q12), dense chosen on a glass marble against a cork ball (nearest L02-q10 and PR-13: the item states "So glass is heavy for its size" before asking the word, so magnetic / strong / smooth are false of the ask), the single MCQ on a material more dense than water (the former multi-select: its two true statements were one fact twice), the shed multi-select (the one set answer).