Safety and evidence boundary
This investigation is data-only and uses supplied synthetic spectra.
Explicit science instruction
Preserve raw peak values before normalization. Processed percentages should be reproducible from the original measurements rather than replacing them.
Normalize each intensity by dividing by total signal, then calculate weighted atomic mass from mass × fractional abundance.
After calculating, compare with a supplied reference and discuss plausible reasons for a small difference such as rounding, calibration assumptions, or incomplete peak capture.
Vocabulary: raw data; normalization; weighted mean; residual difference; uncertainty.
Worked example with reasoning
Raw peaks: mass 28 intensity 92; mass 29 intensity 5; mass 30 intensity 3. Total intensity=100, so abundances are 92%, 5%, 3%. Weighted mass=28(0.92)+29(0.05)+30(0.03)=28.11 u.
Guided question
If total peak intensity is 250 rather than 100, explain how each raw intensity should be normalized before weighting.
Independent work
- Preserve the supplied raw peak table.
- Normalize each intensity to fractional abundance.
- Calculate weighted atomic mass with units.
- Compare with a reference and write one uncertainty statement plus one method revision.
Investigation / Data Lab
Keep the raw spectrum, normalized abundance table, calculation trail, and one revision prompted by the comparison with the reference value.
Misconception check
Normalization does not create new evidence; it rescales the same measurements for comparison. Preserve the raw values.
Formative understanding check
Why should the raw spectrum remain in the evidence record after calculating percentages?
Reveal worked response
Because the raw data are the traceable observations. Normalized values are processed results that should remain reproducible from the originals.
Public self-check only.
Mentor evidence conference
Ask Archaemenes to audit your data lineage from raw intensity to normalized abundance to weighted mass.
Teacher guidance
Foundation: Normalize a two-peak dataset with supplied totals.
Core: Complete a three-peak analysis and uncertainty statement.
Extended: Test how a small missing peak would shift the calculated average.