Physical Science Unit Lab. Mystery Solutions

Transcription

1 Physical Science Unit Lab Mystery Solutions ate,2006 Officer of Forensic Science Unit: Science requires careful observation. s observations are made, often "patterns" emerge that lead to hypothesis and conclusions. Forensic scientists use a variety of precipitation reactions - the formation of an insoluble product. In this experiment, six known solutions of ionic compounds are combined in all combinations. n ionic compound is one, which is formed from positive and negative ions. When two solutions of ionic compounds are mixed, the attraction may be strong enough to cause a solid (precipitate) to be formed. xample 1 Sweat from fingerprints () on rough surface such as wood and investigator's spray ( ) react and form white solid that turns black exposed to sunlight. The chemical reaction can be written as: (aq) + (aq) NaNO 3 (aq) + gl (s) xample 2 The presence of sulfate ion can be detected in urine by precipatation with the barium ion to produce barium sulfate: a(no 3 ) 2 (aq) + Na 2 SO 4 (aq) aso 4 (s) + 2NaNO 3 (aq) Goal: etermine unknown chemicals collected from the crime scene. quipment: - of 6 known solutions in 5 ml pipets - of 6 unknown solutions in 5 ml pipets - of 5 unknown sample solutions from the crime scene in 5 ml pipets - Laminated Table 1, 2, & 3 - Paper towel Grim Hunter, Nancy. 85 ppendix Z

2 Procedure: 1. Obtain a set of 6 known solutions. a. Use the laminated Table 1 with the "dark" squares. dd one drop of the chemical identified at the top of each column onto each dark square in that column. b. dd a drop of the chemical identified at the side of each row onto each dark square in that row. c. Record your observations in the ata Table 1 below. ata Table 1: Known Solution Known set Grim Hunter, Nancy. 86 ppendix Z

3 fter the known solutions have been reacted, solve a set of unknowns Labeled thru F in order to practice your identification skills. The unknowns are the same chemicals as the known set but in a different order. 2. Obtain a set of 6 unknown solutions. a. Use the laminated Table 2 with the "dark" squares. dd one drop of the chemical identified at the top of each column onto each dark square in that column. b. dd a drop of the chemical identified at the side of each row onto each dark square in that row. c. Record your observations in the ata Table 2 below. ata Table 2: Solution F F What is the identity of each of the solutions? is. is. is. is. is. F is. Grim Hunter, Nancy. 87 ppendix Z

4 Your next job will be to investigate crime scene sample solution unknowns by the patterns observed earlier. Not only will you find the identity of the unknowns, but also you will help to find what may have been used to possibly murder the victim from the crime that occurred earlier this week. 3. Obtain a set of 5 unknown crime scene solutions and the set of 6 known solutions from part 1. a. Use the laminated Table 3 with the "dark" squares. dd one drop of the chemical identified at the top of each column onto each dark square in that column. b. dd a drop of the chemical identified at the side of each row onto each dark square in that row. c. Record your observations in the ata Table 3 below. ata Table 3: rime Scene Solution rime Scene (rink in Mug) (Spilled rops on Table) (offee in Pot) (lood xtract) (Water Jug on ounter) Grim Hunter, Nancy. 88 ppendix Z

5 What may be the identity or identities of each of the reactants found in the solutions collected at the crime scene? is. is. is. is. is. re any of these possible reactants known to cause illness or death in people? xplain. Grim Hunter, Nancy. 89 ppendix Z

6 ata Table 1: Known Solution Known set ata Table 2: Solution F F Grim Hunter, Nancy. 90 ppendix Z

7 ata Table 3: rime Scene Solution rime Scene (rink in Mug) (Spilled rops on Table) (offee in Pot) (lood xtract) (Water Jug on ounter) Grim Hunter, Nancy. 91 ppendix Z