Topic 12 — Chemical reactions and conservation of mass — blueprint for James

What I need from you: 5 decisions

1

Open with where the new substance's atoms come from (L01) before naming "chemical reaction" (L02)?

the register makes "atoms are rearranged, not created or destroyed" (MAT-068) a prerequisite of "identify a chemical reaction" (MAT-066), so the fact comes before the name.

the opening scene is steel wool rusting on a balance and gaining 1.2 g; the answer (oxygen atoms from the air joined on) is the whole topic in one picture.

My recommendation: yes, L01 the rusting scene and the fact, L02 the name. Agree / swap them.

2

Show the formula form of an equation only in the three counting lessons (L04, L07, L08)?

the vault rule puts a word equation beside every reaction named in prose; the formula form may sit beneath it but never replace it.

only reading symbols (L04) and counting atoms (L07, L08) need formulas; everywhere else the word equation carries the point without the extra load.

My recommendation: word equation in every lesson; formula form beneath it in L04, L07 and L08 only. Agree / formulas everywhere / formulas nowhere.

3

Include equations written wrong, whose atom counts do not match, as non-examples in L07?

L07 asks the student to count atoms on both sides and confirm they match; a quiz where every answer is "yes, they match" teaches nothing.

two deliberately wrong equations (hydrogen + oxygen written with one water) let the student say "no, the counts differ" — the student is never asked to fix them; balancing stays in high school.

My recommendation: yes, two wrong equations as non-examples, no balancing. Agree / every equation correct.

4

Keep the open-container "mass loss" case inside L06, not as a ninth lesson?

L06 works out a missing mass with the law; its second part heats the same limestone in an open dish and asks where the missing 4.4 g went (into the air as carbon dioxide gas).

the case is the register's MAT-069b applied, and it is the trap every grade-8 test sets; one atom, one lesson, two parts.

My recommendation: keep it as L06 part 2. Agree / make it its own lesson.

5

Which lessons could do without a video?

L01 (oxygen atoms landing on the iron as the mass climbs), L02 (atoms swapping partners), L06 (gas leaving the open dish) and L08 (the willow growing from air and water) have something to watch; L03, L04, L05 and L07 are a format, a look-up, a fact and a count.

My recommendation: mark L03, L04, L05 and L07 "could do without a video"; all eight scripted. Agree / change.

Topic 12 at a glance — 8 lessons

LessonOpens onFormat
L01Where the new substance's atoms come fromSuppose you leave a 10.0 g pad of steel wool damp in the air for a week.video + article
L02A chemical reaction rearranges atomsHere are three before-and-after particle drawings.video + article
L03Reactants and products: the word equationNatural gas burns on a stove.article only
L04Which elements take part: read the symbolsA chemist writes the burning of natural gas with formulas: CH₄ + 2O₂ → CO₂ + 2H₂O.article only
L05The law of conservation of massSuppose a sealed flask holds vinegar and a small packet of baking soda.article only
L06Work out a missing mass, and the open-dish trapSuppose you heat 10.0 g of limestone, calcium carbonate, in a sealed container.video + article
L07Count the atoms on both sidesHere is hydrogen burning, written with formulas: 2H₂ + O₂ → 2H₂O.article only
L08Photosynthesis: a tree's mass comes from the airAbout 400 years ago a scientist planted a small willow tree in a tub of soil.video + article
What this topic is, in five lines

Eight lessons, one per atom: MAT-068, 066, 067, 071, 069, 069b, 070, 072 (register order, prerequisites honoured).

Terms coined here: chemical reaction (L02), reactant, product, word equation (L03), law of conservation of mass (L05). Photosynthesis is named, not coined: its word equation is a Life Science fact retrieved in one sentence (L08).

Deliberately not taught: balancing equations, energy given out or taken in, reaction speed, types of reaction, ions, moles.

An intro video (under 120 words, teaches nothing) opens the topic; a summary video (everything taught, in order, with its own easy question) sits just before the PP100.

The PP100 draws 20 items, tagged easy / medium / hard by depth of reasoning, from a bank of at least 50 four-option MCQs on fresh instances.

Where the new substance's atoms come from L01

Suppose you leave a 10.0 g pad of steel wool damp in the air for a week.

The pad turns brown and crumbly.

Put it back on the balance.

It now has a mass of 11.2 g.

Nobody added anything to it.

Where did the extra 1.2 g come from?

The point, stated first

Where do the atoms in a new substance come from?

They come from the substances that were there before.

The iron atoms in the steel wool joined with oxygen atoms from the air.

Iron atoms and oxygen atoms joined together make the brown substance, iron oxide.

The extra 1.2 g is the mass of the oxygen atoms that joined on.

No atom was made from nothing.

No atom vanished.

Video: oxygen atoms from the air landing on the iron while the mass on the balance climbs from 10.0 g to 11.2 g — video and article (definitely a video).

Part 1 — MAT-068 — Explain where the atoms in the products of a reaction come from

Check: what (the pad's mass after a week: more / less / the same) → why (free response) → misconception item: a student says the change made the rust's atoms — the key corrects: the oxygen atoms came from the air → transfer (a copper roof turns green over years: where did the new atoms come from?)

Figure: SVG: before and after particle boxes, iron atoms alone then iron and oxygen atoms joined, the balance beside each reading 10.0 g and 11.2 g

Leans on: T11 L01 (chemical change: a new substance forms) — one recall question; T7 L01 (atom) — one recall question

A chemical reaction rearranges atoms L02

Here are three before-and-after particle drawings.

In the first, water particles sit close together, then spread apart with the same partners.

In the second, sugar particles sit in a pile, then float among water particles, still whole.

In the third, hydrogen atoms and oxygen atoms let go of their partners and join up as water particles.

Only one of the three shows a new substance forming.

Which one is it?

The point, stated first

How do you tell a chemical reaction from any other change?

Look at the atoms before and after.

In a chemical reaction the atoms let go of their old partners and join new ones.

New groupings of atoms are new substances.

A change in which atoms rearrange into new substances is called a chemical reaction.

Melting and dissolving move the particles around.

The groupings stay the same.

So melting and dissolving are not chemical reactions.

Video: the atoms letting go and re-pairing, next to the melting box where nothing re-pairs — video and article (definitely a video).

Part 1 — MAT-066 — Identify a chemical reaction by recognising that atoms are rearranged to form new substances; coin chemical reaction

Check: example sequence on before-and-after drawings: reaction (hydrogen + oxygen → water) → not (ice melting) → reaction (charcoal burning) → not (sugar dissolving) → reaction (natural gas burning) → rule; fluency quiz: reaction or not, 8 drawings; misconception item: a student says boiling water is a reaction because bubbles form — the key corrects: the water particles are unchanged, they only spread out

Figure: SVG: five before-and-after particle boxes on the fixed glyph palette; "did the atoms change partners?" written under each

Leans on: L01 — one recall question; T7 L04 (molecule) — one recall question; T2 L01 (melting) and T6 L01 (dissolving) — one recall question each

Part 1q — Fluency quiz: chemical reaction

Check: fluency

Figure: —

Leans on: —

Reactants and products: the word equation L03

Natural gas burns on a stove.

Two substances go in: natural gas and oxygen from the air.

Two substances come out: carbon dioxide and water vapor.

A chemist writes all of this on one line with an arrow in the middle.

Which substances belong on the left, and which on the right?

The point, stated first

How do you write down a chemical reaction in one line?

Write the substances that go in on the left.

These are called the reactants.

Write the substances that come out on the right.

These are called the products.

An arrow sits between them.

The arrow reads "react to make".

This line is called a word equation.

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

Part 1 — MAT-067 — Label the reactants and products in a chemical equation; coin reactant, product, word equation

Check: fluency quiz (type a): given a word equation, which substances are the reactants / the products, 8 quick items across the topic's reactions, two options each; one reverse item: write a described reaction as a word equation (typed); misconception item: a student says the arrow means "equals", so the same substances sit on both sides — the key corrects: the arrow means "react to make" and the products are new substances

Figure: SVG: the natural gas word equation typeset large, "reactants" and "products" labelled above the two sides, the arrow labelled "react to make"

Leans on: L02 — one recall question

Part 1q — Fluency quiz: reactant, product, word equation

Check: fluency

Figure: —

Leans on: —

Which elements take part: read the symbols L04

A chemist writes the burning of natural gas with formulas: CH₄ + 2O₂ → CO₂ + 2H₂O.

The letters are chemical symbols.

Each symbol names one element.

Which elements take part in this reaction?

The point, stated first

How do you find every element in a reaction?

Read each capital letter, with any small letter after it, as one symbol.

Look each symbol up on the periodic table.

Write each element down once, however many times its symbol appears.

Natural gas burning uses three elements: carbon, hydrogen and oxygen.

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

Part 1 — MAT-071 — Use the periodic table to identify every element involved in a given chemical reaction

Check: scaffolded (type b): worked case on natural gas burning → step items on a fresh equation (which symbols appear; each symbol → its element from the supplied table) → bare items: list every element in three fresh equations (typed, table supplied); one trap item: CO (two elements) against Co (one element)

Figure: table: the periodic table, supplied in every item; SVG: the equation with each symbol ringed and its element name written beneath

Leans on: T9 L01 (chemical symbols and the capital-letter rule) — one recall question; T9 (find an element on the table) — one recall question; T10 L01 (what a formula tells you) — one recall question; L03

The law of conservation of mass L05

Suppose a sealed flask holds vinegar and a small packet of baking soda.

On the balance the flask has a mass of 250.0 g.

Tip the flask so the vinegar runs onto the baking soda.

The mixture fizzes and the flask fills with gas.

Put it back on the balance.

It still has a mass of 250.0 g.

Why did the mass not change?

The point, stated first

What happens to the total mass in a chemical reaction?

The total mass stays the same.

The atoms only swap partners.

Every atom that was there before is still there after.

Each atom keeps its own mass.

So the total mass of the products equals the total mass of the reactants.

This rule is called the law of conservation of mass.

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

Part 1 — MAT-069 — State the law of conservation of mass; coin law of conservation of mass

Check: fact → repeat back (typed) → what (the sealed flask after fizzing: more / less / the same) → why (free response) → misconception item: a student says the gas that formed has no mass — the key corrects: gas particles are atoms too, each with its mass → transfer (a sealed bag of steel wool rusts for a week: the bag's mass?)

Figure: SVG: the flask on the balance before and after, 250.0 g written on both

Leans on: L01 — one recall question; the grade-5 fact "the total mass stays the same in a sealed jar" (MAT5-060, not taught here) stated in one sentence with one recall item; T1 L04 (a gas is matter and has mass) — one recall question

Part 1q — Fluency quiz: law of conservation of mass

Check: fluency

Figure: —

Leans on: —

Work out a missing mass, and the open-dish trap L06

Suppose you heat 10.0 g of limestone, calcium carbonate, in a sealed container.

It splits into two products: calcium oxide, a white solid, and carbon dioxide, a gas.

The white solid has a mass of 5.6 g.

What is the mass of the carbon dioxide?

The point, stated first

How do you find the mass of one product when you know the others?

Use the law of conservation of mass.

The total mass before equals the total mass after.

So 10.0 g of calcium carbonate makes 5.6 g of calcium oxide plus the carbon dioxide.

The carbon dioxide has a mass of 10.0 g − 5.6 g = 4.4 g.

Now heat the same limestone in an open dish.

The mass on the balance drops by 4.4 g.

No mass was destroyed.

The 4.4 g of carbon dioxide gas floated away into the air.

Video: the gas leaving the open dish as the mass on the balance falls — video and article (definitely a video).

Part 1 — MAT-069b — Calculate the mass of the products of a reaction given the total mass of the reactants

Check: scaffolded (type b): worked case in the full form (the law → the same line in this reaction's substances → make the unknown mass the subject → substitute → calculate, with units) → step items on a fresh reaction (write the line; make the unknown the subject; substitute; calculate) → typed numeric items on two more reactions, one with two reactants and one product

Figure: SVG: the sealed container on the balance before and after with the masses written; the worked form as its own block

Leans on: L05 — one recall question; T3 L02 (mass in grams) — one recall question

Part 2 — MAT-069b — Explain why the mass on the balance drops when a reaction in an open container makes a gas

Check: what (the open dish after heating: mass up / down / the same) → why (free response) → misconception item: a student says the missing 4.4 g was destroyed — the key corrects: it left as carbon dioxide gas, and a sealed container would still read 10.0 g → transfer (a candle burns on a balance and its mass falls: where did the wax's atoms go?)

Figure: SVG: the open dish with the gas drawn leaving, the balance beside it reading 4.4 g less

Leans on: part 1; T1 L04 (a gas has mass) — one recall question

Count the atoms on both sides L07

Here is hydrogen burning, written with formulas: 2H₂ + O₂ → 2H₂O.

The law says no atom is made and no atom is lost.

So the atoms on the left should match the atoms on the right, kind for kind.

Do they?

The point, stated first

How do you check that an equation obeys the law of conservation of mass?

Count the atoms of each element on the left.

Count the atoms of each element on the right.

On the left there are 4 hydrogen atoms and 2 oxygen atoms.

On the right there are also 4 hydrogen atoms and 2 oxygen atoms.

The counts match.

So the equation conserves mass.

If the counts did not match, someone wrote the equation wrong.

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

Part 1 — MAT-070 — Confirm that a given balanced equation conserves mass by counting atoms on each side

Check: scaffolded (type b): worked count on hydrogen burning → step items on natural gas burning (hydrogen on the left; hydrogen on the right; oxygen on the left; oxygen on the right; carbon both sides; do they match?) → bare items: does this equation conserve atoms? yes / no, 6 equations, two of them written wrong (decision 3)

Figure: table: each element's count on the left and on the right; SVG: the atoms drawn as circles above each formula so the student can count them

Leans on: T10 L03 (count atoms with a coefficient, MAT-061) — one recall question; L05 — one recall question

Photosynthesis: a tree's mass comes from the air L08

About 400 years ago a scientist planted a small willow tree in a tub of soil.

The tree had a mass of 2.3 kg.

He watered it for five years and added nothing else.

After five years the tree had a mass of 76.7 kg.

The soil had lost only 0.06 kg.

Where did the other 74 kg of tree come from?

The point, stated first

Where do the atoms in a plant come from?

Plants build a sugar called glucose from carbon dioxide and water.

Light supplies the energy.

This reaction is called photosynthesis.

Count the atoms on each side of the photosynthesis equation.

Every carbon atom in the glucose came from carbon dioxide in the air.

Every hydrogen atom came from the water.

So the tree's 74 kg came from the air and the watering can, not from the soil.

Video: the willow growing while carbon dioxide from the air and water from the can flow into it and the soil stays level — video and article (definitely a video).

Part 1 — MAT-072 — Show that atoms are conserved in the photosynthesis equation by counting atoms on each side

Check: scaffolded (type b): worked count on 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ → step items (carbon left and right; hydrogen left and right; oxygen left and right; do they match?) → bare: does the equation conserve atoms? → misconception item: a student says the tree's extra mass came from the soil — the key corrects: the soil lost 0.06 kg, the atoms came from carbon dioxide and water → transfer (a field of corn gains 5,000 kg over a summer while the soil barely changes: where from?)

Figure: SVG: the willow at 2.3 kg and at 76.7 kg with the soil tub the same in both; table: each element's count on the left and on the right

Leans on: the photosynthesis word equation (LIF-073, Life Science, not taught here) stated in one sentence with one recall item (name its reactants); L07 — one recall question; L06 — one recall question

Topic close

Mixed mastery practice: 12 items; the coined terms by typed recall; one typed missing-mass calculation; one atom count on a fresh equation; one short written answer (where the missing mass went from an open dish).

Then the PP100: 20 items drawn from a bank of at least 50 four-option MCQs on fresh instances and fresh equations, tagged easy / medium / hard by depth of reasoning, at least three per atom, the periodic 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.