Goal: identify the evidence needed to compare material's influence and report actual movement only when a safe, verified matched pair is available. Proposed codes: AC9SFU02, AC9SFI02, AC9SFI03. Prepare: possible broad/light same-shape-and-size pair of verified different materials, exact source labels, flat lane, Card 18.
- Verify · 3 min. Adult checks material labels from preparation/product sources. If UNKNOWN, do not call it a material comparison. Keep the lane and release safe and identical as far as possible.
- Observe before movement · 4 min. Child notices pair shapes/sizes through an accessible route or hears attributed report. Ask whether finish/weight also differs and log that as a limitation.
- Model · 5 min. Use invented Model N to show that even a different endpoint does not reveal which factor mattered when more than one changed.
- Child try · 7 min. If approved pair exists, adult performs each slow release, stopping at catch; Card 18 records source/date, actual result and access. Otherwise child marks NOT TESTED and identifies conditions a later teacher would need.
- Check · 4 min. Offer “The shiny one went farther because it is plastic.” Child corrects to verified material, actual result and other possible differences; a surface look alone is insufficient.
- Exit · 2 min. Leave cause unknown where controlled comparison was not possible; save question for Day 19.