Explicit science instruction
This investigation uses supplied or simulated data so the emphasis remains on analytical reasoning. Students preserve raw distances or signals before processing them.
For chromatography, calculate Rf values and compare patterns under the same conditions. For spectroscopy, use a supplied calibration or reference pattern.
A defensible conclusion distinguishes what the evidence directly shows from what is inferred about component identity or concentration.
Vocabulary: raw signal; processed data; reference; calibration; uncertainty.
Worked example with reasoning
Unknown chromatogram U has two spots with Rf 0.32 and 0.74. Reference mixture R contains spots at 0.31 and 0.75 under the same conditions. The pattern is strongly consistent, but measurement uncertainty should be reported.
Guided question
Which is stronger evidence of a match: one similar Rf value or a multi-component pattern under identical conditions? Explain.
Independent work
- Preserve the raw measurement table.
- Calculate all Rf or calibration-derived values.
- Compare unknown and reference patterns.
- Write a conclusion with uncertainty and one alternative explanation.
Investigation / Data Lab
Preserve raw distances/signals, processed ratios or concentrations, reference comparison, uncertainty, and one revision.
Misconception check
Processed ratios and concentrations should not replace raw observations in the evidence record.
Formative understanding check
Why preserve both raw and processed analytical data?
Reveal response
The processed result must remain traceable and reproducible from the original observations.
Mentor evidence conference
Ask Archaemenes to separate direct analytical evidence from inference and audit the uncertainty statement.
Teacher guidance
Foundation: Use a guided raw/processed table.
Core: Complete comparison and uncertainty analysis.
Extended: Evaluate an ambiguous unknown using multiple evidence streams.