Canonical lesson CHEMISTRY20-U1-L15 · outcome 20-A2.2k · depth CURRICULUM_BASELINE

Unit A: Diversity of Matter and Chemical Bonding - outcome 20-A2.2k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U1-L15
• Official outcome: 20-A2.2k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

explain why formulas for molecular substances refer to the number of atoms of each constituent element

Learning intention

Meet 20-A2.2k with instruction, practice, and a check. The 10-session bootcamp does not replace this lesson.

Success criteria

1. Restate the outcome in classroom language without swapping in a different unit’s template.
2. Complete the worked-style task for this outcome.
3. Name the lab setting (classroom-supervised / teacher demo / dataset or simulation / forbidden).

Teaching

A molecular formula states how many atoms of each element are in one molecule, not a reduced ionic ratio. H2O2 is hydrogen peroxide (two H, two O in the molecule). Reducing it to HO would describe a different substance. C6H12O6 is not CH2O even though the empirical formula is CH2O.

Worked example

Ethene is C2H4 (one molecule has two C and four H). The ionic-style “lowest ratio” CH2 would be the empirical formula, not the molecular formula used for naming and Lewis structures.

Guided practice

1. Glucose C6H12O6 vs empirical CH2O: which is used for naming and Lewis counts? Do not copy ethene only.
2. Near-miss: reducing C2H4 to CH2 and naming it methane. Mark the first wrong line.

Independent practice

1. Hydrogen peroxide H2O2 vs HO: which is the molecular formula?
2. Two sentences: ionic Al2O3 vs molecular N2O4 - different meaning of the subscripts.
3. Count atoms in one molecule of P4O10.

Diagram / whiteboard

Approved diagram id chem20-ionic-lattice - Ionic lattice / bonding sketch. Tutor may open the course whiteboard and display this id. Do not invent hazardous procedures on the board.

Checks for understanding

Use the formative evidence below as the exit check for this outcome. Correct the misconception named in this lesson before praising.

Misconception to repair

Always reducing molecular formulas the way ionic formulas are reduced.

Safety and lab register

Setting: classroom-supervised only for Session 04 conductivity (NaCl / sucrose / ~5% vinegar, 9 V LED or school probe). All other Unit A work is paper, models, data cards, or approved simulation. Forbidden: bleach+acid, bleach+ammonia, flames, tasting, home copy of Session 04, concentrated acids/bases, generating Cl2. AI Tutor must not invent labs outside CHEM20_LOW_RESOURCE_LAB_REGISTER.csv.

Alberta Poison Control if a real exposure is occurring: 1-844-764-7669. The AI Tutor is not a poison centre.

Formative evidence

State molecular vs empirical for C2H4 and one naming consequence.

This is not a diploma. Mastery needs instruction + activity + check.

AI Tutor / human tutor

Ground on 20-A2.2k. No false praise. No invented procedures. No silent skip to a different unit. Human tutor if the student describes mixing bleach, tasting, or flames.

Provenance

Official POS wording from ALBERTA_SENIOR_HIGH_OFFICIAL_OUTCOMES.csv. Pack lesson written to replace Wave-4 contaminated canonical markdown.