Canonical lesson CHEMISTRY20-U4-L11 · outcome 20-D2.1k · depth CURRICULUM_BASELINE

Unit D: Quantitative Relationships in Chemical Changes - outcome 20-D2.1k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U4-L11
• Official outcome: 20-D2.1k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

explain chemical principles (i.e., conservation of mass in a chemical change), using quantitative analysis

Learning intention

Meet 20-D2.1k 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

Conservation of mass: in a closed chemical change, total mass of reactants equals total mass of products. Quantitative analysis (masses, moles from a balanced equation) demonstrates the principle. Gases that escape an open flask make it look like mass was lost - that is an experimental design issue, not a failure of the law.

Worked example

2.00 g S + 3.00 g O2 (excess unused separated) producing 4.00 g SO2 if S is limiting and all S converts (check with moles). Open-beaker carbonate + acid: CO2 leaves; remaining mass drops. Closed container: mass constant.

Guided practice

1. Closed flask: 2.00 g S + enough O2, product 4.00 g SO2 if S limiting as in the worked logic - check with moles. Open beaker acid + carbonate: why mass drops.
2. Near-miss: “mass disappeared” in the open beaker without naming CO2(g). Mark it.

Independent practice

1. When is mass conserved experimentally (closed vs open)?
2. Two sentences: atoms conserved; gas can leave an open system.
3. No home acid + carbonate fizz as a required lab - dataset ok.

Diagram / whiteboard

Approved diagram id chem20-stoich-mole-map - Mole map stoichiometry flow. 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

“Mass is lost because gas has no mass.”

Safety and lab register

Setting: stoichiometry on balanced equations and provided mass/volume data. Live combustion or precipitation is teacher demo or school lab SOP only - never a home task. Titration (if run) is school burette, dilute reagents, goggles; otherwise use the provided titration-curve dataset. Forbidden: student-run flames, concentrating acids, tutor-invented yields labs. AI Tutor must not invent procedures.

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

Formative evidence

One closed-system number check and one open-system explanation.

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

AI Tutor / human tutor

Ground on 20-D2.1k. 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.