Canonical lesson CHEMISTRY20-U3-L25 · outcome 20-C2.5k · depth CURRICULUM_BASELINE

Unit C: Solutions, Acids, Bases and Equilibrium intro - outcome 20-C2.5k

• Course: CHEMISTRY20 (SCN2796)
• Lesson ID: CHEMISTRY20-U3-L25
• Official outcome: 20-C2.5k (KNOWLEDGE)
• Object type: canonical lesson (not a bootcamp session)
• Source: Alberta Chemistry 20 Program of Studies (2007, updated 2014)

Official outcome text

compare magnitude changes in pH and pOH with changes in concentration for acids and bases

Learning intention

Meet 20-C2.5k 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

pH is logarithmic: each 1-unit pH change is a tenfold change in [H3O+]. ΔpH = 2 means 100-fold concentration change. Diluting a strong acid 10× raises pH by about 1 (if still far from 7).

Worked example

From pH 1.00 to 3.00, [H3O+] falls from 0.10 to 0.0010 mol/L (100×). A base from pH 13 to 12 is a 10× drop in [OH−].

Guided practice

1. If pH rises from 2.00 to 5.00, by what factor does [H3O+] fall? Do not copy 1.00→3.00 only.
2. Near-miss: “pH 2 to pH 3 is a 1% change.” Mark the first wrong line.

Independent practice

1. Base: pH 12.00 to 14.00 - factor change in [OH−].
2. Two sentences: logarithmic scale.
3. One order of magnitude = factor of 10.

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

Thinking pH 3 is “three times less acidic” than pH 1.

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 acid and one base factor-of-change item.

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

AI Tutor / human tutor

Ground on 20-C2.5k. 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.