This packet is everything a parent or guide needs to assess Unit 07 at home — learning targets, the answers that count as correct, the mastery rubric, calibration examples, and a clipboard score sheet. No multiple-choice test: the student shows mastery by running a titration to the equivalence point and computing an unknown concentration.
By the end of the Acids & Bases unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Titrate to the equivalence point; find the unknown concentration.
The student explains pH on a log scale (Page 4).
Burette readings, calculation, and result kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Not yet, Approaching, or Mastered — the column language tells you which. A criterion counts as mastered only when the student can both run the titration and defend the calculation. A student carries three tokens per term; one token buys a re-do of one criterion on another day, so a single bad afternoon never sinks the unit.
Accept any answer in the synonyms column — they are pre-approved as equivalent. The third column flags the confusions that look close but are not yet, so you can coach precisely.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Defining acids & bases | ||
| Brønsted–Lowry acid | proton donor | Donates H⁺; base accepts it — broader than Arrhenius |
| pH | −log[H⁺] | A log scale — one unit is a 10× change in [H⁺] |
| Strong vs weak acid | full vs partial dissociation | Strength ≠ concentration; a weak acid can still be concentrated |
| Neutralization | acid + base → salt + water | Produces water and a salt; not always pH 7 at equivalence |
| Solutions & titration | ||
| Molarity (M) | moles per liter | Concentration; use M₁V₁ = M₂V₂ for dilution |
| Equivalence point | stoichiometric point | Moles of acid = moles of base; the indicator endpoint approximates it |
| Buffer | weak acid/conjugate pair | Resists pH change; not the same as “neutral” |
| Indicator | pH dye (e.g. phenolphthalein) | Signals the endpoint by color change; choose to match the equivalence pH |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Acid–base definitions & pH | Confuses acids and bases or the pH scale direction. | Defines acids and bases but stumbles on the log nature of pH. | Applies Arrhenius and Brønsted–Lowry definitions and computes pH on the log scale. |
| Concentration & solution prep | Cannot relate moles, volume, and molarity. | Calculates molarity but mishandles dilution. | Prepares solutions of known concentration and uses dilution (M₁V₁ = M₂V₂) correctly. |
| Titration & the equivalence point | Does not connect titration to a calculation. | Runs a titration but misidentifies the equivalence point. | Titrates to the equivalence point and solves for an unknown concentration. |
| Buffers & solubility | Treats all solutions as fully soluble and unbuffered. | Defines a buffer but cannot predict its behavior. | Explains how buffers resist pH change and predicts relative solubility. |
| Lab technique (titration) | Overshoots the endpoint and misreads the burette. | Titrates but records volumes imprecisely. | Titrates with clean technique, reads the endpoint precisely, and computes the result. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
The split between Approaching and Mastered is endpoint discipline: a careful titration stops one drop past the color change. Ask to see the burette readings — precise initial and final volumes, not a single “about 25 mL.”
Read these before you grade. They show what Mastered and Not yet actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Acid–base definitions & pH | NY / Appr / Mast | |
| 2 | Concentration & solution prep | NY / Appr / Mast | |
| 3 | Titration & the equivalence point | NY / Appr / Mast | |
| 4 | Buffers & solubility | NY / Appr / Mast | |
| 5 | Lab technique (titration) | NY / Appr / Mast | |
| 6 | Integration (cross-domain) | NY / Appr / Mast |
☐ No ☐ Yes — for criterion: __________ Tokens remaining: ☐ 3 ☐ 2 ☐ 1 ☐ 0
NY = Not yet · Appr = Approaching · Mast = Mastered · Unsure between two levels? Circle the lower one and note what a re-do would need.