Topic 4 — Density — blueprint for James

What I need from you: 4 decisions

Teach density qualitatively first (L02), then the calculation (L03), as two lessons?

MAT-009 decides which of two objects is denser without calculating; MAT-010 calculates density with units. The register keeps them apart, and the Teaching Equations guide says vary each variable qualitatively before the formula.

L02 compares two same-sized cubes on a balance, then two same-mass samples in a cylinder; L03 states density = mass ÷ volume and works three examples.

My recommendation: two lessons, in that order. Agree / merge.

Units: grams per cubic centimeter throughout, with 1 mL = 1 cm³ stated once?

liquids are measured in mL (Topic 3); solids by displacement in mL of water moved; densities are quoted in g/cm³ in every textbook and test.

L01 states once, with a drawing, that 1 mL of water fills a 1 cm cube, so 1 mL and 1 cm³ are the same volume.

My recommendation: g/cm³ everywhere, the equivalence stated once in L01 and recalled where used. Agree / prefer g/mL.

Typed numeric answers, exact value, unit required?

L03 items give mass and volume that divide cleanly (48 g and 6 cm³ → 8 g/cm³); L01 items subtract two cylinder readings.

the page accepts "8", "8 g/cm3", "8 g/cm³"; a wrong unit is marked wrong with a hint.

My recommendation: yes; no rounding needed anywhere in this topic. Agree / other.

Which lessons could do without a video?

something moves in L01 (the water level rising), L02 (two cubes on a balance tipping), L04 (sinking and floating). L03 is a worked calculation; L05 is an explanation.

My recommendation: mark L03 and L05 "could do without a video"; all five scripted. Agree / change.

Topic 4 at a glance — 5 lessons

	Lesson	Opens on	Format
L01	Find the volume of an odd-shaped solid	A student wants the volume of a small stone.	video + article
L02	Which is denser?	Two cubes sit on a table, exactly the same size.	video + article
L03	Calculate density	A steel cube has a mass of 48 g.	article only
L04	Will it sink or float?	A student drops a steel bolt into a bucket of water, and it sinks.	video + article
L05	Density does not depend on how much you have	A student cuts a 48 g steel cube in half.	article only

What this topic is, in five lines

Five lessons, one per atom: MAT-008, 009, 010, 011, 015.

Terms coined here: displacement (L01), density (L02), g/cm³ as the unit (L03).

Deliberately not taught: buoyancy as a force, why density is a "characteristic property" beyond what L05 says, densities of gases, rounding.

Find the volume of an odd-shaped solid L01

A student wants the volume of a small stone.

The stone is lumpy, with no flat sides to measure.

A ruler gives her nothing useful.

She has a measuring cylinder with 40 mL of water in it.

How can the water tell her the stone's volume?

The point, stated first

How do you measure the volume of a shape a ruler cannot handle?

Drop the stone into the water, and the level rises.

The stone pushes aside exactly its own volume of water.

The water rose from 40 mL to 52 mL, so the stone's volume is 12 mL.

Pushing the water aside is called displacement.

1 mL of water fills a cube 1 cm on each side, so 12 mL is 12 cm³.

Video: the level rising as the stone goes in — video and article.

Part 1 — MAT-008 — Calculate the volume of an irregular solid from the start and end readings of a graduated cylinder; coin displacement, state 1 mL = 1 cm³

Check: scaffolded (type b): worked example on the page (40 mL → 52 mL, 12 cm³) → step items (read the start; read the end; subtract) on a fresh drawn pair → two bare typed items (readings given as numbers) → one with surplus information (the stone's mass, to ignore)

Figure: SVG: the cylinder before and after, levels at 40 mL and 52 mL, the stone drawn in; a 1 cm cube beside a 1 mL drop

Leans on: T3 L03 (reading a cylinder in mL) — one recall question

Part 1q — Fluency quiz: displacement

Check: fluency

Figure: —

Leans on: —

Which is denser? L02

Two cubes sit on a table, exactly the same size.

One is steel; one is wood.

A student lifts them: the steel cube is far heavier.

The two cubes are the same size but not the same heft.

What is different about the steel?

The point, stated first

Why can two objects of the same size have different masses?

The steel cube packs more mass into the same volume.

How much mass a material packs into each bit of volume is called its density.

Same volume, more mass: the steel is denser than the wood.

Same mass, less volume: also denser.

Video: the balance tipping under the steel cube; the two 100 g samples in cylinders — video and article.

Part 1 — MAT-009 — Decide which of two objects is denser given their mass and volume, without calculating; coin density

Check: example sequence: same volume, more mass → denser; same mass, more volume → less dense; then fluency quiz: which is denser, 6 pairs shown as small tables (mass and volume of each), no calculation needed because one quantity matches; misconception item: a student says the heavier object is always denser — the key corrects: only at the same volume

Figure: table: the pairs compared — mass, volume, which is denser; SVG: two same-sized cubes on a balance, steel side down

Leans on: T3 L02 (mass) and T3 L03 (volume) — one recall question each; MAT5-002 retrieved

Part 1q — Fluency quiz: density (the meaning in plain words)

Check: fluency

Figure: —

Leans on: —

Calculate density L03

A steel cube has a mass of 48 g.

A wooden block has a mass of 48 g too.

The steel cube has a volume of 6 cm³; the wooden block, 80 cm³.

Both have the same mass, so the comparison trick from last time will not settle a number.

How dense is each one, as a number?

The point, stated first

How do you turn "denser" into a number?

Density is the mass of each cubic centimeter.

Divide the mass by the volume.

The steel's density is 48 g ÷ 6 cm³, which equals 8 g/cm³.

The wood's density is 48 g ÷ 80 cm³, which equals 0.6 g/cm³.

The unit says it: grams per cubic centimeter.

Video: nothing a page cannot show — article only; the worked form is on the page.

Part 1 — MAT-010 — Calculate the density of a substance from its mass and volume, with correct units; coin the unit g/cm³

Check: scaffolded (type b): worked example in the worked form (values, equation, substitute, calculate, answer) → step items on a fresh case (write the values; which equation; substitute; calculate) → two bare typed items, clean division → one with the volume found by displacement first (two readings given)

Figure: SVG: the worked form laid out as the page shows it; table: three materials with mass, volume, density

Leans on: L02 (density in words), L01 (cm³) — one recall question each

Will it sink or float? L04

A student drops a steel bolt into a bucket of water, and it sinks.

She drops a wooden block, and it floats.

Then she drops a small plastic bead into the water, and it floats.

She drops the same bead into a bucket of cooking oil, and it sinks.

Same bead, two liquids, two outcomes.

What decides?

The point, stated first

What decides whether something sinks or floats?

You compare the object's density with the liquid's density.

An object denser than the liquid sinks.

An object less dense than the liquid floats.

The bead has a density of 0.95 g/cm³.

Water has a density of 1.0 g/cm³, so the bead floats in water.

Cooking oil has a density of 0.92 g/cm³, so the same bead sinks in oil.

Video: objects sinking and floating in two liquids — video and article.

Part 1 — MAT-011 — Predict whether an object will sink or float in a given liquid by comparing their densities

Check: fluency quiz (type a): sink or float, 8 items each giving the object's and the liquid's density in a two-row table; one misconception item: a student says heavy things sink — the key corrects: density decides, not mass; transfer: an object denser than water but less dense than a named liquid

Figure: table per item (object density / liquid density); SVG: the bucket with a sinker and a floater, densities labelled

Leans on: L02 and L03 (density, g/cm³) — one recall question each; MAT5-002 retrieved

Notes

Scene note for L04: the bead is polyethylene (0.95 g/cm³); every density a check needs is given in the stem, so no memorised values are needed.

Density does not depend on how much you have L05

A student cuts a 48 g steel cube in half.

Each half has a mass of 24 g.

Each half has a volume of 3 cm³.

Is each half less dense than the whole cube?

The point, stated first

Does a small piece of a material have the same density as a big piece?

Yes: cutting the cube in half halves the mass and halves the volume.

24 g ÷ 3 cm³ = 8 g/cm³, the same as the whole cube.

Density belongs to the material, not to the size of the piece.

So a tiny steel filing and a steel girder both have a density of 8 g/cm³.

Video: nothing a page cannot show — article only.

Part 1 — MAT-015 — Explain why the density of a small sample and a large sample of the same substance are identical

Check: what (a gold ring and a gold bar: which is denser — the same) → why (free response with the numbers) → misconception item: a student says the bar is denser because it is heavier — the key corrects: more mass and more volume in the same ratio → transfer (half a glass of water vs a full glass)

Figure: table: whole cube / half cube — mass, volume, density

Leans on: L03 (calculate density) — one recall question; MAT4-001 retrieved

Topic close

Mixed mastery practice: 10–12 items; the coined terms by typed recall (displacement, density, the unit g/cm³); three typed calculations (a displacement volume; a density; a density after displacement); sink-or-float items with a table; one short written answer (why the half cube has the same density).

Then the PP100: 20 four-option MCQs on fresh instances, tagged easy / medium / hard by depth of reasoning, at least one item per atom; numbers that divide cleanly.

The course architecture (14 topics) — open only if you want the whole map

Skill: course-build → atomise (architecture, step 6b gate) → write-like-james @ 4c9e849

MS Chemistry — course architecture v1 (for James's approval, 25 September 2026)

Read this in five minutes. It decides the topics, their order, where every PP100 sits, and which topic pilots first. Nothing below writes a lesson sentence. The atom register stays where it is: the Matter strand of the Science Knowledge Graph (92 atoms, JM-reviewed). This document arranges those 92 atoms into a course and stops.

The takeaways

Fourteen topics, one PP100 at the end of each, 92 lessons in all. One atom, one lesson. Topics run 4 to 12 atoms; the average is 6 or 7.
The order follows the big ideas, not the TEKS list: what matter is and how particles explain it → what properties tell you → sorting matter into kinds → inside the atom and the periodic table → how matter changes → two grade-8 applications (water, acids and bases).
Topic 1 is the pilot: "Particles and the three states of matter", 12 lessons. It stresses every treatment the course will need — a two-part test taught by examples, a fact, two "explain the smell" mechanisms, three example-sequence classifications, three particle-picture why-lessons, one coined term with a ranking routine. Its blueprint is the second deliverable.
Density is its own topic. It carries the course's first two calculation routines, so it gets its own practice set and PP100 (vault ruling: a quantitative subtopic becomes its own topic).
Three checkpoint tests, at the three natural seams, anchored to the released grade-8 STAAR, Florida SSA and AZSCI forms. Grade-level slices remain derivable from the TEKS stamps if operations later want them.
Five prerequisites live in other strands and are not taught here. Each lesson that leans on one states it in a sentence and asks one recall question. Nothing is assumed (stand-alone entry rule).
Seven register observations for your atomisation pass. No atom was edited; the register is read-mostly.

Status (25 September, later the same day): you approved Topic 1 as the pilot and clarified delivery (video or article per atom, then questions). Card 5 records that. The ask now: approve or edit the Topic 1 blueprint (course_preview/review/BLUEPRINT_T01.html); lesson writing starts on your word.

Card 1 — The topics

The call: fourteen topics in the order below, a mixed mastery practice set then a PP100 at the end of every one.

#	Topic (student-facing title)	Atoms	Lessons	TEKS stamp	The big idea it serves
1	Particles and the three states of matter	MAT-001, 002, 003, 004, 016, 016b, 017, 017b, 018, 018b, 019, 019b	12	6.6A	Everything is made of moving particles; that explains solids, liquids and gases
2	Changing state	MAT-020, 021, 022, 023, 024, 025, 026, 026b	8	6.6A (NGSS MS-PS1-4)	Heating and cooling change how particles move, not what they are; mass holds
3	Physical properties	MAT-005, 006, 007, 012, 013	5	6.6D	Properties you can measure without changing the substance
4	Density	MAT-008, 009, 010, 011, 015	5	6.6D	A property that identifies a substance whatever the sample size
5	Pure substances and mixtures	MAT-027, 028, 029, 030, 032	5	6.6B	Sorting matter by how many kinds it contains
6	Solutions and separating mixtures	MAT-033, 034, 035, 036, 037, 038, 039, 040, 041	9	7.6D, 7.6E, pre-6.6B	A mixture keeps its parts' properties, so you can pull it apart
7	Atoms, elements, molecules and compounds	MAT-042, 042b, 043, 044, 045, 046, 047, 048	8	7.6A	One kind of atom or more than one: the particle-level sort
8	Inside the atom	MAT-049, 050, 051, 051b, 052	5	(NGSS MS-PS1-1; FL SC.8.P.8.7)	Protons decide which element an atom is
9	The periodic table	MAT-053, 054, 054b, 055, 056, 057, 058	7	6.6C	The table arranges elements so position predicts properties
10	Chemical formulas	MAT-059, 059b, 060, 061	4	7.6B	A formula counts atoms; change the count and you change the substance
11	Physical and chemical change	MAT-062, 063, 064, 064b, 065, 065b	6	7.6C	Did a new substance form? The one test, and its evidence
12	Chemical reactions and conservation of mass	MAT-066, 067, 068, 069, 069b, 070, 071, 072	8	8.6E, 8.6B	Reactions rearrange atoms; none appear or vanish, so mass holds
13	Water's special properties	MAT-073, 074, 075, 076	4	8.6C	Water particles pull on each other and on other surfaces
14	Acids and bases	MAT-077, 078, 079, 080, 081, 082	6	8.6D	Two families of substance, one scale, and what happens when they meet

Totals: 92 lessons, 14 practice sets, 14 PP100s (280 items), 3 checkpoint tests. Two atoms may need a second lesson once blueprinted — MAT-010 (calculate density) and MAT-061 (coefficients and parentheses) — so plan for 92 to 94.

Why this grouping

Every prerequisite edge in the register points backwards in this order. Checked atom by atom; no forward reference.
Sub-domains 2 and 3 were each split in two (Topics 3/4 and 1/2). SD-3 has 16 atoms; a 20-item PP100 over 16 atoms certifies nothing. SD-2 bundles a calculation routine with observational properties.
Topics 5 to 7 form one sort of matter in three passes: by how many substances (5), by whether it is a solution (6), by what the particles are (7). The full classification tree (MAT-047) closes Topic 7.
Topics 13 and 14 sit last. Nothing depends on them, they are the register's only pure grade-8 applications, and the checkpoint before them then covers a clean block.

What changes: the course folder gets one topicNN_build/ folder per topic; Topic 1's blueprint is written; nothing else is authored until you approve it.

Card 2 — Topic 1 is the pilot, at 12 lessons

The call: pilot "Particles and the three states of matter" end to end — 12 lessons, quiz after each, mixed practice, PP100 — before any other topic starts.

Why

The vertical-slice rule asks for a routine, a categorical concept and an explanation in the pilot. Topic 1 has all three: three example-sequence classifications (solid, liquid, gas), three why-lessons on the particle picture, a ranking routine that coins the course's first technical term, and a transformation (heating speeds particles).
It is the course's foundation. Every later topic reuses its one particle picture and its four sentences about arrangement and movement.
SD-1 alone (4 atoms) would pilot fast but would not test a PP100 worth the name, and has no routine.

The alternative is a 10/10 cut: move the two kinetic-energy atoms (MAT-019, 019b) to the front of Topic 2, where kinetic energy is the lever for melting. I kept them in Topic 1 because TEKS 6.6A names kinetic energy in the states comparison, and the ranking closes the three-box picture.

What changes: the Topic 1 blueprint is the next thing you read.

Card 3 — Density stands alone

The call: Topic 4 "Density" (5 atoms) is separate from Topic 3 "Physical properties" (5 atoms).

Why

Density carries two routines (displacement volume, MAT-008; calculate density, MAT-010) plus the sink-or-float prediction and the "same whatever the sample size" fact.
Vault ruling (AP Biology, 10 Sep 2026): a topic test that mixes a calculation routine with a content topic hides which one failed.
Solubility (MAT-012) and conductors (MAT-013) stay in Topic 3 as properties; Topic 6 retrieves solubility with a recall question.

What changes: two PP100s where the register had one sub-domain.

Card 4 — Checkpoints at three seams

The call: three static checkpoint tests, each with some free response, at the ends of Topics 6, 10 and 14; the third doubles as the end-of-course test and is anchored to released grade-8 STAAR, Florida SSA and AZSCI items.

Why

The seams are natural: Topics 1–6 are matter you can see and handle; 7–10 are the atom and its table; 11–14 are change and two applications.
No state tests middle-school science before grade 8, so there is no per-grade instrument to anchor to (HANDOFF recommendation 1). The TEKS stamps (6.x/7.x/8.x on every atom) still allow a grade-level slice later without re-atomising.
Five interchangeable forms per test is the standing ruling for topic tests; whether checkpoints also get five forms is your call.

What changes: nothing yet. Checkpoints are built after the topics they cover.

Card 5 — Delivery: video or article per atom, quiz straight after

The call: every lesson (one per atom) ships as BOTH a 40–90 second video and a short article, and the student chooses which to take; the quiz follows in the app, never inside the video. At topic end: mixed mastery practice (any format, key terms by recall), then the PP100 (20 MCQs, easy/medium/hard). No topic intro or summary videos.

Why

Your format ladder of 25 September, with your clarification the same day: each atom is a video with the option to read the article instead. The platform's learner's-choice mode carries exactly that.
When video and text are alternatives, each must teach the whole part (vault rule), so the video script (write-video-script) and the article (write-lesson) are written from the same blueprint row and reviewed against each other.
Pitched one notch up from the Grade 3 Forces pack: no title slide, open on the first example, rule stated last, everything appears on the word that names it. Middle school may carry a short "why" where Grade 3 stayed qualitative.
The ladder names no intro or summary video. AP Biology and HS Chemistry ran different intro policies; I have not inherited either.

Skills that run per lesson, in order: write-lesson (dispatching by lesson type) for the article → write-video-script for the video → design-check-sequence then write-mcqs for the quiz → review-accuracy (a reader who did not write it, against the reference) → review-figures on every rendered figure → review-lesson (blind key read, guidance read, adjudication) → blind review of every key before anything ships.

Figures: the blueprint names the figure kind per part. Particle pictures are always monochrome SVG drawings, one depiction reused everywhere. Real scenes a student should recognise (a tea bag colouring water, sand pouring into a jar) are licensed stock photos where the photo carries the point; a drawing where the point is a measurement or a label.

What changes: the blueprint carries a delivery line and an SVG-or-photo call on every figure.

Card 6 — Five prerequisites are taught in other strands

The call: the five cross-strand prerequisites below are not taught in MS Chemistry. Each lesson that leans on one states the fact in one sentence and asks one recall question before using it.

External atom	What it says	Leaned on by
ENE-020	Temperature measures average particle motion	MAT-004 (Topic 1)
ENE-021	Heat flows from hot to cold	MAT-020–023 (Topic 2)
ENE-025	Thermal conductors and insulators	MAT-013 (Topic 3)
FOR-017	Spot a magnetic force	MAT-041 (Topic 6)
LIF-073	The photosynthesis word equation	MAT-072 (Topic 12)

Why

Stand-alone entry rule: no student has taken the 3–5 courses or the sibling MS courses, so every lesson stands alone.
One loop to know about: ENE-020 (Energy) lists MAT-002 and MAT-003 as its prerequisites, and MAT-004 lists ENE-020. Inside this course MAT-004 carries the "hotter means faster particles" idea itself; the Energy course will meet it as retrieval.

What changes: the blueprint's "leans on" column names the external atom wherever it applies.

Card 7 — Register observations, no edits made

The call: seven observations for your atomisation pass. I changed nothing in the register.

MAT-013 sorts materials as thermal and electrical conductors — two property families in one behaviour (the "and" audit). Candidate split.
MAT-022 "Evaporation and boiling" — evaporation happens at the surface below the boiling point; boiling happens throughout at one temperature. Two predictions, one atom. Candidate split.
MAT-050 states the charge and location of three particles — six facts in one contrast frame. HS Chemistry kept a similar profile atom whole as an argued exception; flagging for the same argument here.
MAT-061 counts atoms with "a coefficient, parentheses, or both" — two routines, likely two lessons.
MAT-019b may not fail independently of MAT-019 in practice. Kept as its own lesson; the data decides (guide: never pre-emptively merge).
MAT-004 → MAT-016/017/018. Identifying a solid from its behaviour does not need "heating speeds particles". The edge is honoured in the order, but it looks like a sequencing edge rather than a knowledge one.
MAT-042 has no in-strand prerequisite and enters via MAT5-084 only; Topic 7 must open with the particle picture from Topic 1 as its retrieval.

What changes: nothing until you rule. Atom edits happen in the knowledge-graph repo with a log entry.

About this build (kickoff record)

Register: Science Knowledge Graph/data/atoms/06-08/matter.json, pulled 25 September 2026, 92 atoms in 13 sub-domains. Per-course choices are the register's: K-8 IDs with letter suffixes; Fact / Categorical / Transformation / Routine; bare behaviours; verdict/reason split by default.
Endpoint: grade-8 STAAR, Florida SSA and AZSCI physical-science items; NGSS MS-PS1-1/2/4/5.
Sources read: knowledge-graph HANDOFF and CLAUDE; vault CLAUDE, 00 Protocol, the PP100 and build-process-v2 rulings, the blueprint rule; the Grade 3 Forces feedback log; the chemistry misconception research (particle model area). HS Chemistry Unit 1 was opened before this document was written; under your same-day correction it is reference only, and Topic 1's scenes were chosen fresh.
Coverage check (standards mapped onto this architecture, never the other way): every Matter atom sits in exactly one topic; every TEKS 6.6/7.6/8.6 knowledge code in the register appears in at least one topic. Blank cells in the register (e.g. NGSS on solutions, TEKS on atomic structure) are register findings, not gaps in this course.

What happens next

You approve or edit the topic table. Then you read the Topic 1 blueprint. Only after that does write-lesson run on Topic 1, one lesson at a time, starting with the first of each lesson type as its exemplar.