Forensics is a chemistry event that involves identification of powders, polymers, fibers, and hair samples, blood serum and fingerprint analysis, and interpretation of chromatography. Given a scenario and some possible suspects, students will perform a series of tests. These tests, along with other evidence or test results will be used to solve a crime. This event is closely associated with the Division B event, Crime Busters.
1 or 2 people per team. Eye protection #4. 50 minutes.
Students should bring:
- Test tubes and test tube holders (or any devices in which they can perform the tests)
- Funnels and/or filter paper
- pH or litmus paper
- Spatulas, plastic spoons, and/or stirring rods
- 9-volt conductivity meter (not AC current)
- Flame test equipment (nichrome wire, cobalt blue glass, etc.)
- Slides and cover slips
- Hand lens
- Writing instruments
- A pencil and ruler (for chromatograms)
- Paper towels
- Metal tongs
- A 8.5".11" two sided page of any notes containing information in any form from any source
- Non-programmable calculator
Event proctors will provide:
- Iodine reagent
- 2M HCl
- 2M NaOH
- Benedict's solution
- Hot water bath
- A Bunsen burner or something similar
- A waste container
- Chromatography materials
- A wash bottle with distilled water
Event proctors may provide:
- Other equipment (microscope, probes, etc.)
- Candle & matches if fibers given
- Differential density solutions or other method of determining density if plastics are given
- Reagents to perform other tests
- Qualitative Analysis (powders)
- Fingerprint Analysis
- Glass Analysis
- Seeds and Pollen
- Tracks and Soil
- Bullet Striations
Methods of Identification:
- Flame test
- Tests with liquids: Iodine, Sodium Hydroxide, Hydrochloric Acid, Benedict's solution, Water, Ammonium Chloride
- solubility in water
- Try to use solubility
- How they react with the chemicals provided
- Utilize pH
- Burn tests can be used if necessary, but are only effective with K, B, and Li compounds (because their color is really distinct).
- Becoming familiar with the chemicals is the key to success. Memorizing properties and reactions of powders will greatly aid in their identification.
Methods of Identification
- Burn test (fibers and hair only)
- Density in liquids--oil, water, alcohol, etc. (plastics)
- Burn tests for fibers, when permitted, will usually be done with a small candle (Bunsen burners are too hot).
- Burn tests on plastics will not be permitted at the event, but burn test results may be provided. If not, it is important to know densities and other identifying properties.
- Common liquids used to test plastic densities include water, vegetable oil, isopropyl alcohol, and NaCL solution.