Topic 10 — Chemical formulas — blueprint for James

What I need from you: 5 decisions

1

Split MAT-061 into two lessons, a number in front first and then parentheses, making five lessons?

MAT-061 asks the student to count atoms when a formula has a coefficient, parentheses, or both. A coefficient multiplies every atom in the particle; a subscript after parentheses repeats only the group inside them.

those are two different moves, and a student can be right about one and wrong about the other. The architecture (Card 1) allows a fifth lesson here.

My recommendation: five lessons; L04 coefficients, L05 parentheses, with the both-together cases closing L05. Agree / one lesson.

2

Teach counting atoms (L02) before "change a subscript, change the substance" (L03)?

the register lists MAT-059b (why a changed subscript makes a new substance) before MAT-060 (count the atoms). Both need only MAT-059, so either order is allowed.

a student who can already count H₂O and H₂O₂ sees at once that the second particle holds one more oxygen atom, so the "different particle, different substance" point lands on a count they can do.

My recommendation: yes, count first, then the why. Agree / register order.

3

Call the thing a formula describes "one particle of the substance" for every compound, and leave ions out?

water and carbon dioxide come in molecules; table salt and the parentheses compounds (magnesium hydroxide, calcium nitrate) do not, and the honest account needs ions, which this course does not teach.

"one particle of the substance holds these atoms in these counts" is true enough for every formula at this grade and lets every formula be drawn on Topic 7's glyph palette.

My recommendation: "one particle" throughout; ions and the molecule-or-not distinction go in "deliberately not taught". Agree / molecules only in lessons / other.

4

Use only real substances with everyday names, never made-up formulas?

every formula in a lesson or item can be a substance the student has met (water, carbon dioxide, table salt, natural gas, sugar, milk of magnesia) with its name given once.

an invented formula like X₂Y₃ tests the routine cleanly but teaches a student that formulas are letter games.

My recommendation: real substances only, the name given once beside each formula; the bank of 50 has enough of them. Agree / allow invented formulas in the bank.

5

Which lessons could do without a video?

L01 (the drawn particle collapsing into its formula) and L03 (one atom added and the label switching to a new substance) have something to watch; L02, L04 and L05 are counting routines a worked table shows.

My recommendation: mark L02, L04 and L05 "could do without a video"; all five scripted. Agree / change.

Topic 10 at a glance — 5 lessons

LessonOpens onFormat
L01What a formula saysA bottle of water is labeled H₂O.video + article
L02Count the atoms in a formulaTable sugar has the formula C₆H₁₂O₆.article only
L03Change a subscript, change the substanceH₂O is water; you drink it.video + article
L04A number in front: coefficientsIn Topic 12 you will meet a line that reads 2H₂O.article only
L05Parentheses: a group repeatedMilk of magnesia is a medicine for an upset stomach.article only
What this topic is, in five lines

Five lessons: MAT-059, 060, 059b, and MAT-061 split across two lessons (teaching order below; every prerequisite edge points backwards).

Terms coined here: chemical formula and subscript (L01), coefficient (L04). Parentheses keep their everyday name.

Retrieved, not re-coined: atom, element, molecule, compound (T7), chemical symbol (T9), "a compound is not like its elements" (T7 L08).

Deliberately not taught: ions and ionic compounds, naming compounds from formulas, writing a formula from a name, balancing equations (Topic 12), the mole.

Also in this topic: an intro video before L01 (under 120 words, teaches nothing: "a formula is a recipe that counts atoms; change one count and you have a different substance") and a summary video just before the PP100 (everything taught, in teaching order, with its own easy question).

The PP100 is 20 items, easy / medium / hard by depth of reasoning, drawn from a bank of at least 50 four-option MCQs on real substances, a symbol-to-name table supplied in every item that needs it.

What a formula says L01

A bottle of water is labeled H₂O.

A fire extinguisher is labeled CO₂.

Topic 7 drew a water particle as one large atom joined to two small ones.

Now the same particle is written as one letter, a small 2 and another letter.

What does each letter say, and what does the small 2 count?

The point, stated first

What do the letters and the small numbers in a formula tell you?

The letters are chemical symbols, so each symbol names one element in the particle.

The small number written low after a symbol is called a subscript.

A subscript counts the atoms of the element just before it in one particle.

A symbol with no subscript stands for one atom.

So H₂O is one particle of two hydrogen atoms and one oxygen atom.

This way of writing a substance is called its chemical formula.

Video: the drawn water particle collapsing into H₂O, each atom flying to its letter and the two hydrogens to the 2 — video and article (definitely a video).

Part 1 — MAT-059 — Explain what the symbols and subscripts in a chemical formula represent; coin chemical formula, subscript

Check: what: three two-option items (the H names: hydrogen / a count; the 2 counts: hydrogen atoms / oxygen atoms; no subscript means: one atom / no atoms) → misconception item: a student says the 2 in H₂O counts the oxygen atoms — the key corrects: a subscript counts the symbol just before it → transfer: read CO₂ and NH₃ aloud as counts

Figure: SVG: the water particle drawn beside H₂O, a line from each symbol to its atom and from the subscript 2 to the two hydrogen atoms; the same for CO₂ under a subtitle

Leans on: T9 L01 (chemical symbol) and T7 L05 (compound) — one recall question each

Part 1q — Fluency quiz: chemical formula, subscript

Check: fluency

Figure: —

Leans on: —

Count the atoms in a formula L02

Table sugar has the formula C₆H₁₂O₆.

One sugar particle is built from many atoms.

How many carbon atoms, how many hydrogen atoms, how many oxygen atoms, and how many atoms in all?

The point, stated first

How do you count the atoms in a formula?

Take the symbols one at a time.

Read the subscript after each symbol; that subscript is the count of that element's atoms.

A symbol with no subscript counts one atom.

Add the counts together for the total.

Sugar holds 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms, which makes 24 atoms in one particle.

Video: nothing a page cannot show — article only (could do without a video).

Part 1 — MAT-060 — Count the atoms of each element in a formula that contains only subscripts

Check: scaffolded (type b): worked count of C₆H₁₂O₆ → step items on CH₄, natural gas (list the elements; count each; total) → 8 bare typed-numeric items on fresh real formulas (NH₃, H₂O₂, CaCO₃, C₃H₈, NaCl, SO₂), each asking one element's count or the total; misconception item: a student says H₂O₂ holds 2 atoms — the key corrects: 2 hydrogen and 2 oxygen, 4 atoms

Figure: table: formula / element / count / total, filled for sugar and then for natural gas under a subtitle; SVG: the CH₄ particle drawn beside its formula

Leans on: L01 (subscript) — one recall question

Change a subscript, change the substance L03

H₂O is water; you drink it.

H₂O₂ is hydrogen peroxide; it bleaches hair and stings in a cut.

The two formulas differ by one small 2.

CO is a poisonous gas; CO₂ is the gas you breathe out.

Why does one small number make a different substance?

The point, stated first

Why does changing a subscript change the substance?

A subscript counts the atoms in one particle.

Change the count and you have built a different particle.

A different particle is a different substance, with its own properties.

So H₂O₂ is not water with a little extra oxygen; hydrogen peroxide is a different substance from water.

Video: one oxygen atom joining the drawn water particle and the label switching from water to hydrogen peroxide — video and article (definitely a video).

Part 1 — MAT-059b — Explain why changing a subscript in a chemical formula produces a different substance

Check: what: is H₂O₂ water? (yes / no) → why (free response: "H₂O₂ is a different substance from H₂O because…") → misconception item: a student says H₂O₂ is just water with a bit more oxygen mixed in — the key corrects: the particle itself is different, so the substance is different → transfer: O₂ (the oxygen we breathe) and O₃ (ozone, a gas that is poisonous to breathe)

Figure: SVG: the water particle and the hydrogen peroxide particle drawn side by side, formula under each, the extra oxygen atom ringed; table: water / hydrogen peroxide, one property each in the identical frame; CO and CO₂ as the second example set under a subtitle

Leans on: L02 (counting) — one recall question; T7 L08 (a compound is not like its elements) — one recall question

A number in front: coefficients L04

In Topic 12 you will meet a line that reads 2H₂O.

A big 2 sits in front of the formula, on the line, not written low.

Does that 2 count hydrogen atoms, the way a subscript does?

The point, stated first

What does a number in front of a formula mean?

A number in front counts whole particles, and it is called a coefficient.

2H₂O means two water particles.

One water particle holds 2 hydrogen atoms and 1 oxygen atom.

Two water particles hold 4 hydrogen atoms and 2 oxygen atoms.

So a coefficient multiplies every count in the formula.

Video: nothing a page cannot show — article only (could do without a video).

Part 1 — MAT-061 (first half) — Count the atoms of each element in a formula that has a coefficient; coin coefficient

Check: scaffolded (type b): worked count of 2H₂O → step items on 3CO₂ (count in one particle; how many particles; multiply) → 8 bare typed-numeric items (4NH₃, 5O₂, 2C₆H₁₂O₆, 3CH₄), per element and total; misconception item: a student says 2H₂O holds 2 + 2 = 4 hydrogen atoms and 1 oxygen atom — the key corrects: the coefficient multiplies every element, so 4 hydrogen and 2 oxygen

Figure: SVG: two water particles drawn side by side above 2H₂O, each atom counted; table: formula / particles / atoms per particle / atoms in all

Leans on: L02 (counting) — one recall question

Part 1q — Fluency quiz: coefficient — does this number count atoms or particles? 6 items

Check: fluency

Figure: —

Leans on: —

Parentheses: a group repeated L05

Milk of magnesia is a medicine for an upset stomach.

Its formula is Mg(OH)₂.

Parentheses wrap the O and the H, and a small 2 follows the closing parenthesis.

What does that 2 count?

The point, stated first

What does a subscript after a closing parenthesis count?

The parentheses hold a group of atoms, here one oxygen atom and one hydrogen atom.

The subscript after the parentheses repeats the whole group.

(OH)₂ means two oxygen atoms and two hydrogen atoms.

Mg(OH)₂ holds 1 magnesium atom, 2 oxygen atoms and 2 hydrogen atoms, which makes 5 atoms.

When a coefficient sits in front as well, multiply every count once more.

Video: nothing a page cannot show — article only (could do without a video).

Part 1 — MAT-061 (second half) — Count the atoms of each element in a formula that has parentheses

Check: scaffolded (type b): worked count of Mg(OH)₂ → step items on Ca(NO₃)₂ (what is inside the parentheses; repeat it; add the atoms outside) → 6 bare typed-numeric items (Al(OH)₃, Ca(OH)₂, Mg(NO₃)₂), per element and total; misconception item: a student says the 2 in Mg(OH)₂ counts only the hydrogen atoms — the key corrects: it repeats everything inside the parentheses

Figure: SVG: the OH group drawn twice inside a bracket beside one magnesium atom, above Mg(OH)₂; table: formula / inside the parentheses / times repeated / count

Leans on: L02 (counting) — one recall question

Part 2 — MAT-061 (both together) — Count the atoms of each element in a formula that has both a coefficient and parentheses

Check: scaffolded (type b): worked count of 2Mg(OH)₂ → step items on 3Ca(OH)₂ (count one particle, parentheses first; then multiply by the coefficient) → 4 bare typed-numeric items (2Al(OH)₃, 3Ca(NO₃)₂), per element and total

Figure: SVG: two Mg(OH)₂ particles drawn above 2Mg(OH)₂; table: the two steps as two rows

Leans on: part 1 and L04 — one recall question each

Topic close

Mixed mastery practice: 10–12 items; the coined terms by typed recall; four typed counts mixing plain, coefficient, parentheses and both; one short written answer (why H₂O₂ is not water).

Then the summary video (everything taught, in order, with its own easy question).

Then the PP100: 20 items drawn from a bank of at least 50 four-option MCQs on fresh real formulas, tagged easy / medium / hard by depth of reasoning, at least three per atom (MAT-061 counted as two), a symbol-to-name table supplied in every stem that needs it.

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

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)AtomsLessonsTEKS stampThe big idea it serves
1Particles and the three states of matterMAT-001, 002, 003, 004, 016, 016b, 017, 017b, 018, 018b, 019, 019b126.6AEverything is made of moving particles; that explains solids, liquids and gases
2Changing stateMAT-020, 021, 022, 023, 024, 025, 026, 026b86.6A (NGSS MS-PS1-4)Heating and cooling change how particles move, not what they are; mass holds
3Physical propertiesMAT-005, 006, 007, 012, 01356.6DProperties you can measure without changing the substance
4DensityMAT-008, 009, 010, 011, 01556.6DA property that identifies a substance whatever the sample size
5Pure substances and mixturesMAT-027, 028, 029, 030, 03256.6BSorting matter by how many kinds it contains
6Solutions and separating mixturesMAT-033, 034, 035, 036, 037, 038, 039, 040, 04197.6D, 7.6E, pre-6.6BA mixture keeps its parts' properties, so you can pull it apart
7Atoms, elements, molecules and compoundsMAT-042, 042b, 043, 044, 045, 046, 047, 04887.6AOne kind of atom or more than one: the particle-level sort
8Inside the atomMAT-049, 050, 051, 051b, 0525(NGSS MS-PS1-1; FL SC.8.P.8.7)Protons decide which element an atom is
9The periodic tableMAT-053, 054, 054b, 055, 056, 057, 05876.6CThe table arranges elements so position predicts properties
10Chemical formulasMAT-059, 059b, 060, 06147.6BA formula counts atoms; change the count and you change the substance
11Physical and chemical changeMAT-062, 063, 064, 064b, 065, 065b67.6CDid a new substance form? The one test, and its evidence
12Chemical reactions and conservation of massMAT-066, 067, 068, 069, 069b, 070, 071, 07288.6E, 8.6BReactions rearrange atoms; none appear or vanish, so mass holds
13Water's special propertiesMAT-073, 074, 075, 07648.6CWater particles pull on each other and on other surfaces
14Acids and basesMAT-077, 078, 079, 080, 081, 08268.6DTwo 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

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 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

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

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

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 atomWhat it saysLeaned on by
ENE-020Temperature measures average particle motionMAT-004 (Topic 1)
ENE-021Heat flows from hot to coldMAT-020–023 (Topic 2)
ENE-025Thermal conductors and insulatorsMAT-013 (Topic 3)
FOR-017Spot a magnetic forceMAT-041 (Topic 6)
LIF-073The photosynthesis word equationMAT-072 (Topic 12)

Why

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.

  1. MAT-013 sorts materials as thermal and electrical conductors — two property families in one behaviour (the "and" audit). Candidate split.
  2. 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.
  3. 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.
  4. MAT-061 counts atoms with "a coefficient, parentheses, or both" — two routines, likely two lessons.
  5. MAT-019b may not fail independently of MAT-019 in practice. Kept as its own lesson; the data decides (guide: never pre-emptively merge).
  6. 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.
  7. 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)

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.