Canonical lesson CHEMISTRY20-U2-L03 · outcome 20-B1.3k · depth CURRICULUM_BASELINE

Unit B: Gases - outcome 20-B1.3k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U2-L03
• Official outcome: 20-B1.3k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

explain the law of combining volumes

Learning intention

Meet 20-B1.3k 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

Gay-Lussac’s law of combining volumes: at the same T and P, volumes of gaseous reactants and products are in small whole-number ratios. Avogadro’s hypothesis explains this: equal volumes of gases at the same T and P contain equal numbers of particles, so volume ratios match mole ratios from the balanced equation.

Worked example

2 H2(g) + O2(g) → 2 H2O(g): 2 L hydrogen combine with 1 L oxygen to give 2 L steam if all are measured at the same T and P. N2(g) + 3 H2(g) → 2 NH3(g): 1 : 3 : 2 volume ratio - not gram-ratio stoichiometry.

Guided practice

1. N2(g) + 3 H2(g) → 2 NH3(g): volumes at the same T and P. Do not convert to grams unless asked.
2. Near-miss: using 28 g : 2 g mass ratio as the volume ratio. Mark the first wrong line.

Independent practice

1. 2 H2 + O2 → 2 H2O(g): litres of O2 needed for 4.0 L H2 (same T, P).
2. Two sentences: Gay-Lussac combining volumes vs mole-mass stoichiometry.
3. Why all gases in the statement must be at the same T and P.

Diagram / whiteboard

Approved diagram id chem20-pv-boyle - P-V Boyle sketch (or gas law axes). 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

Applying combining volumes to solids or aqueous ions, or confusing volume ratios with gram ratios.

Safety and lab register

Setting: datasets, simulations, and teacher demo of sealed apparatus only. Students do not generate gases, open compressed cylinders, or heat with flame. Boyle/Charles work uses a provided P-V or V-T table or PhET-class simulation. Forbidden: generating chlorine, hydrogen, or ammonia gas; dry ice in a sealed bottle as a student task; any kitchen-stove Charles’s-law balloon. AI Tutor must not invent gas-generation procedures.

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

Formative evidence

Volume ratio for ammonia synthesis and one wrong-unit warning.

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

AI Tutor / human tutor

Ground on 20-B1.3k. 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.