This packet is everything a parent or guide needs to assess Unit 04 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 separating an unknown and stating what each test can and cannot establish.
By the end of the Chromatography & Chemical Analysis unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Separate an unknown, calculate Rf, compare to a known.
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 Not yet, Approaching, or Mastered — 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. 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 |
|---|---|---|
| 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 |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Chromatography principles & the Rf value | Cannot explain what makes components separate. | Describes the setup but cannot compute or interpret an Rf value. | Explains mobile and stationary phases and calculates a reproducible Rf value for each component. |
| Ink & dye separation | Runs a plate but reads nothing from the result. | Separates a sample but cannot compare it to a known. | Separates an unknown ink or dye and compares its pattern and Rf values against a known standard. |
| Presumptive vs. confirmatory testing | Treats a presumptive result as a final identification. | Names the two test types but confuses what each can establish. | Distinguishes presumptive from confirmatory tests and states what each can and cannot prove. |
| Analyzing an unknown systematically | Guesses the identity of a sample without a procedure. | Runs tests but in no logical order and without narrowing possibilities. | Works an unknown through an ordered scheme, narrowing possibilities before confirming. |
| Technique, controls & documentation | Omits controls or keeps no record of the run. | Runs the test but handles controls or documentation inconsistently. | Runs proper controls, documents each step, and reports results with their limits. |
| Integration (cross-domain) | Treats chemical analysis as isolated facts; makes no cross-domain connection. | Names a link from chemical analysis to history, reading, or writing but cannot defend why it matters. | Connects chromatography and chemical analysis to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
The split between Approaching and Mastered is presumptive vs. confirmatory: not just running a test, but stating what its result can and cannot establish. Ask “does that positive screen the sample, or confirm what it is?”
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 | Chromatography principles & the Rf value | NY / Appr / Mast | |
| 2 | Ink & dye separation | NY / Appr / Mast | |
| 3 | Presumptive vs. confirmatory testing | NY / Appr / Mast | |
| 4 | Analyzing an unknown systematically | NY / Appr / Mast | |
| 5 | Technique, controls & documentation | 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.