Crime Busters

Crime Busters is a skills-oriented chemistry event in Science Olympiad.  Students are given a scenario and evidence collected at the scene of the (non-violent) crime.  They analyze the clues in order to solve the crime.  You can see a good description of the event at  Crime Busters on SciOly, a student wiki for Science Olympiad for exchanging tips and resources.  Note that gypsum is plaster of Paris and calcium carbonate is chalk.

Half the points are earned in the analysis portion in which students need to identify an unknown powdered solid, a liquid, and a metal.


These are pictures from the powdered solid analysis.  What you see are 11 of the 13 possibilities that I actually had around my house, even acetic acid (being a bread baker.)  Sand (go figure) and sodium acetate were the only two I did not have.

Other things you need are Lugol's iodine (not alcohol-based like the stuff at the pharmacy) hydrochloric acid (HCl), and pH paper, all available along with acetic acid from Home Training Tools.  They include instructions to make a 3M HCl solution.  You may want to get a brown glass bottle to store it in as well, and a 10 ml graduated cylinder to measure it out (though not necessary.)

The coolest reaction: vitamin C (acetic acid) turns iodine from brown to completely clear.