Canonical lesson CHEMISTRY20-U3-L24 · outcome 20-C2.4k · depth CURRICULUM_BASELINE

Unit C: Solutions, Acids, Bases and Equilibrium intro - outcome 20-C2.4k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U3-L24
• Official outcome: 20-C2.4k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

use appropriate Système international (SI) units to communicate the concentration of solutions and express pH and concentration answers to the correct number of significant digits; i.e., use the number of decimal places in the pH to determine the number of significant digits of the concentration

Learning intention

Meet 20-C2.4k 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

Report pH to the same number of decimal places as there are significant digits in the coefficient of [H3O+] after scientific notation rules: [H3O+] = 2.5 × 10−4 has two sig figs in 2.5 → pH 3.60. Concentration mol/L uses SI and sig figs from the measurements. Do not write pH = 3.6 as 3.600 without data.

Worked example

If [H3O+] = 3.0 × 10−5, pH = 4.52 (two decimal places from two sig figs in 3.0). 0.10 mol/L → two sig figs → pH 1.00.

Guided practice

1. [H3O+] = 2.5 × 10−4 → pH with correct decimals. Do not copy 3.0 × 10−5 only.
2. Near-miss: pH 3.60206 from 2.5 × 10−4 reported to five decimals. Mark extra digits.

Independent practice

1. pH 8.20 → [H3O+] with sig figs from two decimal places.
2. Two sentences: decimal places in pH ↔ sig figs in concentration.
3. SI unit for concentration in the log argument (mol/L implied).

Diagram / whiteboard

Approved diagram id chem20-ph-scale - pH scale / solution concentration 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

Copying extra calculator digits (pH = 2.30102999).

Safety and lab register

Setting: concentration and pH on paper or school-prepared dilute solutions. Red-cabbage indicator is classroom-supervised or photo/dataset. No concentrated acids or bases. No tasting. Dilution math is not a licence to mix cleaners. Forbidden: bleach+acid, drain opener, battery acid, undiluted pool chemicals. AI Tutor must not invent titrations or acid labs outside the register.

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

Formative evidence

One pH from concentration and one concentration from pH, digits justified.

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

AI Tutor / human tutor

Ground on 20-C2.4k. 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.