Forensics: Cheat Sheet Scioly

Add (some turn yellow) and pH paper results. 2. Polymer Identification (Plastics) Memorize common recycling codes & density tests:

Add (PS dissolves; others don’t). 3. Hair & Fiber Analysis | Type | Cuticle pattern | Medulla | Cross-section | Burn test | |------|----------------|---------|---------------|------------| | Human | Imbricate (scaly) | Fragmented/trace | Round/oval | Burns quickly, chemical smell | | Cat | Spinous (petal-like) | Unbroken chain | Round | Burnt hair smell | | Dog | Spinous | Thick, unbroken | Oval | Burnt hair smell | | Cotton | Twisted ribbon | None | Bean/kidney | Burns to ash, paper smell | | Wool | Scaly | None | Round | Burnt hair, self-extinguishes | | Polyester | Smooth | None | Round | Melts, beads, no ash | forensics cheat sheet scioly

| Substance | Solubility (Water) | HCl reaction | Iodine test | Flame test color | |-----------|--------------------|--------------|-------------|------------------| | Baking soda | Slightly soluble | Fizzes | No change | Yellow-orange | | Baking powder | Fizzes (acid + base) | Fizzes | No change | Yellow | | Cornstarch | Insoluble | No fizz | Blue-black | Yellow (burns) | | Plaster of Paris | Slightly soluble | No fizz | No change | Orange-red (Ca) | | Sugar | Soluble | No fizz | No change | Melts → brown | Add (some turn yellow) and pH paper results

| Code | Polymer | Density (g/mL) | Float? (Water) | Burn test | |------|---------|----------------|----------------|------------| | 1 | PETE | 1.38–1.39 | Sinks | Smells sweet | | 2 | HDPE | 0.95–0.97 | Floats | Paraffin smell | | 3 | PVC | 1.30–1.58 | Sinks | Acrid, HCl gas | | 4 | LDPE | 0.92–0.94 | Floats | Paraffin smell | | 5 | PP | 0.90–0.91 | Floats | Clean burning | | 6 | PS | 1.04–1.09 | Sinks (but slow) | Sooty, floral | A well-designed cheat sheet (one double-sided page, 8

Purpose of the Cheat Sheet In the Science Olympiad Forensics event, teams analyze crime scene evidence—powders, hairs, fibers, fingerprints, polymers, and more. A well-designed cheat sheet (one double-sided page, 8.5" x 11" or letter size) serves as your instant reference for tests and lab stations . It won’t teach you the material, but it will save you when you forget a flame test color or a polymer ID code. Key Sections to Include 1. Physical Properties of Powders (White Solids) Create a quick grid: