Use these targets, vocabulary, rubrics, examples, and score sheet with the instructor's approved lesson and procedure. This is an assessment companion, not a complete lesson or safety authorization.
Student lessons, data, and public practice answers (not assessment keys): Unit 04 learning pathway.
The student demonstrates the following:
Five science criteria plus separately reported integration (Page 3).
Measure two-band paper chromatograms under two conditions, calculate Rf, compare to references.
The student states presumptive vs. confirmatory (Page 4).
The run, the Rf values, and the honest limit kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Developing, Proficient, or Mastery — the column language tells you which. A criterion counts as mastered only when the student can both run the separation and state its honest limits. Each student has three tokens per term; each token retries one rubric criterion. Approved accommodations, equipment failures, and approved absences are handled separately and do not consume these tokens.
Accept listed synonyms; use the distinction column to resolve near-matches.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Separation | ||
| Chromatography | separation technique | Pulls a mixture apart by how fast components move |
| Mobile / stationary phase | moving vs. fixed phase | The solvent carries components across the fixed medium |
| Rf value | retention factor | Distance moved ÷ solvent distance — a repeatable number, not a color |
| Testing & limits | ||
| Presumptive test | screening test | Narrows possibilities; a positive is not an identification |
| Confirmatory test | identifying test | Establishes identity; needed before you claim what it is |
| Control | known standard; blank | Run alongside so a result can be trusted |
| Questioned vs. known | unknown vs. reference | Evidence of unknown origin compared to a standard |
| Consistent, not identical | consistent with | What a presumptive comparison can honestly report |
The split between Proficient and Mastery is presumptive vs. confirmatory: a second nonspecific result does not establish specificity. Ask for the blank, reference, hidden QC, and the valid calibration range before accepting a concentration or identification claim.
| Criterion | Developing | Proficient | Mastery |
|---|---|---|---|
| Chromatography principles & the Rf value | Cannot explain separation or define the ratio. | Computes a ratio without a valid origin/front. | Explains mobile/stationary phases; computes dimensionless per-run Rf values, repeated-reading spread, and invalid-front cases from supplied diagrams. |
| Ink & dye separation | Identifies ink from appearance alone. | Compares one band or solvent only. | Compares two-band mixtures with references across both supplied solvent conditions; retains compatible and excluded references without asserting unique identity. |
| Presumptive vs. confirmatory testing | Treats a screen as a final identification. | Names confirmation but ignores specificity. | Distinguishes screening from validated confirmation; explains co-migration, interference, and why repeating the same screen is not independent confirmation. |
| Analyzing an unknown systematically | Guesses a concentration or identity. | Uses a calibration without blank correction or range checks. | Fits the supplied standard curve, subtracts the blank, calculates unknown concentration and QC recovery, and rejects extrapolation or human-effect claims. |
| Technique, controls & documentation | Omits controls or original readings. | Records controls without acting on failure. | Retains coded paper measurements, independent readings, blank/reference status, and failed runs; distinguishes arithmetic checks from empirical method validation. |
| Integration (cross-domain) | Makes no supported connection between the source and the science. | Uses the source but needs help connecting evidence, writing, or limitations to the science. | Independently connects History, Reading, and Writing using a cited source, appropriate evidence, a limitation, and a scientific explanation. |
Read these before you grade. They show what Mastery and Developing actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Chromatography principles & the Rf value | Dev / Prof / Mast | |
| 2 | Ink & dye separation | Dev / Prof / Mast | |
| 3 | Presumptive vs. confirmatory testing | Dev / Prof / Mast | |
| 4 | Analyzing an unknown systematically | Dev / Prof / Mast | |
| 5 | Technique, controls & documentation | Dev / Prof / Mast | |
| 6 | Integration (cross-domain) | Dev / Prof / Mast |
☐ No ☐ Yes — for criterion: __________
Tokens left this term after this session (choose one): ☐ 3 ☐ 2 ☐ 1 ☐ None left
Dev = Developing · Prof = Proficient · Mast = Mastery · Unsure between two levels? Circle the lower one and note what a re-do would need.