Canonical lesson CHEMISTRY20-U1-L22 · outcome 20-A2.9k · depth CURRICULUM_BASELINE

Unit A: Diversity of Matter and Chemical Bonding - outcome 20-A2.9k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U1-L22
• Official outcome: 20-A2.9k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

determine the polarity of a molecule based on simple structural shapes and unequal charge distribution

Learning intention

Meet 20-A2.9k 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 molecule is polar if it has polar bonds and the bond dipoles do not cancel. Shape decides cancellation. CO2 is linear: two C=O dipoles cancel → nonpolar molecule. H2O is bent: dipoles add → polar. CCl4 tetrahedral: cancels → nonpolar. CHCl3 does not cancel → polar.

Worked example

NF3 is trigonal pyramidal: N-F dipoles plus lone pair → polar. BF3 trigonal planar → nonpolar.

Guided practice

1. Polar or nonpolar: CHCl3 vs CCl4. Do not copy NF3/BF3 only.
2. Near-miss: “all molecules with polar bonds are polar.” Mark the first wrong line using CO2 or BF3.

Independent practice

1. Polarity of H2O vs CO2 with shapes.
2. Two sentences: vector cancellation.
3. Predict polarity of PF3.

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

Calling any molecule with polar bonds polar (forgetting CO2 and CCl4).

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

Label NF3 polar and BF3 nonpolar with one shape reason each.

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

AI Tutor / human tutor

Ground on 20-A2.9k. 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.