What this event is about
Div B forensics: qualitative analysis and evidence matching to support a likely sequence of events.
Study plan
Setup (team of 2, ~50 min, Eye Protection C, Class II calculator each, one double-sided sheet each, Chemistry Events Lab Equipment List items)
- Pack PPE (goggles, apron/lab coat, covered skin, hair tied) and allowed lab gear; ES provides iodine reagent, 1M HCl, chromatography materials, waste container, wash bottle.
- Qualitative analysis (~50%): build a decision tree for listed solids (incl. starred mixture solids), non-powdered metals, and liquids using solubility, acidity, magnetism, color, density, odor.
- Practice 2- and 3-solid mixtures at the counts your tournament level allows (Regionals up to 2 of 2 solids with *; State 2–4 of 2–3; Nationals 2–6 of 2–3).
- Polymers/natural (~10%): human vs dog vs cat hair; animal vs vegetable vs synthetic fibers; recyclable plastics PETE, HDPE, non-expanded PS, LDPE, PP, PVC, PMMA (burn results may be given — no burn tests).
- Paper chromatography (~5%): run inks/juices/Kool-Aid® style samples, calculate Rf carefully, keep chromatograms for turn-in.
- Physical evidence (~10%): fingerprint patterns (whorls/loops/arches); DNA chromatogram/electropherogram compares; shoeprints & tire treads (direction/speed, no calc); soil composition links; spatter direction/speed (no calc).
- Analysis write-up (~25%): name culprit(s) with evidence, explain why others are cleared, answer ES analysis questions.
- Scale practice to level evidence counts (Regionals 6–15 QA unknowns; State 10–18; Nationals 14–20) and clean up — up to 10% penalties for mess or prohibited equipment.
Tips
Keep a clean evidence log. Never cross-contaminate samples.