Safety boundary
Use paper models, supplied data, and approved simulations only. No unsupervised reactive mixtures are required.
Explicit chemistry instruction
A mass-to-mass problem follows a chain: grams known → moles known → mole ratio → moles target → grams target.
Preserve each conversion factor so the reasoning remains traceable and unit cancellation can be checked.
This investigation uses supplied or simulated data only; no chemical mixing is required.
Vocabulary: mass-to-mass stoichiometry; conversion chain; predicted yield; unit audit; residual.
Worked example
For 2H₂ + O₂ → 2H₂O, 32.0 g O₂ is 1.00 mol O₂, predicting 2.00 mol H₂O or about 36.0 g H₂O with excess H₂.
Guided question
Which step in a mass-to-mass chain uses the balanced-equation coefficients?
Independent work
- Preserve the supplied mass data.
- Convert to moles.
- Apply a mole ratio.
- Convert predicted product moles to mass and compare with a reference.
Investigation / Data Lab
Use supplied or simulated reaction data only. Preserve raw quantities, conversion chain, predicted value, residual, uncertainty, and one revision.
Misconception check
Skipping the mole step usually produces an invalid gram ratio unless special masses happen to align.
Formative check
What is the required bridge between grams of different substances?
Reveal response
Moles and the balanced-equation mole ratio.
Mentor evidence conference
Ask Archaemenes to audit units, conversion factors, equation coefficients, and model assumptions.
Teacher guidance
Foundation: Use a four-step conversion scaffold.
Core: Complete one full mass-to-mass prediction.
Extended: Quantify residual error against supplied reference data.