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Science Crime Busters

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Forum Thread: 2009 2010

Test Exchange: 2009 2010

1 Description
2 Survival Kit
3 Before the competition (at school practices)
4 Charts
5 Chromatography
6 Fingerprints
7 Polymers (Not part of 2010 event)
8 At the Competition
9 Scoring
10 Practice Tests

Description

Students will identify perpetrators of a certain crime by using fiber or hair identification, analyzing shoe prints, tire treads, paper chromatography, and fingerprints. Students will also be asked to identify different powders, metals, and liquids by performing multiple tests.

Survival Kit

Every team must bring a bunch of stuff in order just to get into the testing room. The team must have:

Lab aprons or coats
Splash Goggles
Pencils (NOT PENS, you will most likely make mistakes)

Also, the team should have the following:

Standard sheet of paper (both sides) with handwritten notes on anything involved with the event! Make sure they're handwritten, and as of 2010 only one sheet of notes is allowed, per team.
Extra pencil for chromatography
Paper Towels
Magnet
Microscope Slides
TESTING TRAYS!!
PH paper
Wood Splints (Make sure you have extra)
Some form of scoop for the powders

The supervisor will provide everything else you need, so if you bring it you will be penalized.

Before the competition (at school practices)

Check with your SO Coach to get the following materials to test:

Powders(Italics means it can be used in mixtures)
- White Sand
- Calcium Carbonate
- Table Salt
- Sugar
- Flour
- Cornstarch
- Gypsum
- Baking Soda
- Powdered Gelatin
- Powdered Alka-Seltzer
- Sodium Acetate
- Vitamin C
- Yeast
Metals
- Aluminum
- Copper
- Iron
- Tin
- Zinc
- Magnesium
Liquids
- Rubbing Alcohol
- Household Ammonia
- Water
- Vinegar
- Hydrogen Peroxide
- Lemon Juice

The coach will also need a dropper bottle of 3M HCl (hydrochloric acid) and Iodine, pH or Litmus paper, 15-20 containers for testing, 15-20 unknowns, a Magnet, Wood Splints or plastic spoons, a container of Water, an eye dropper, a hand lens, and chromatography materials.

Make a chart for testing. For Powders, include color, reactions with water, HCl, and Iodine; Smell (distinct, faint, or none); Crystal shape (if any), whether it dissolves or not, and reaction to pH or Litmus paper. For metals, include reactions to water and HCl and Magnetic property (yes or no). For Liquids, include smell, reactions to pH or litmus, and color. With your teammate, memorize the results (this is where two heads are better than one) and try testing unknowns made by the coach or other team members. If you can do this, it helps very much when it comes time for the competition. After you do that, learn how to identify fibers/hairs using a hand lens.

Charts

Powders

Powder	Crystal Shape	Color	Solubility	pH	HCl	Iodine	Notes
Sodium Acetate	powder	white	yes	9	none	none	it kinda clumps in water
Sand	random	white	no	7	none	none	does nothing, may have black specks
Calcium Carbonate	powder	white	no	7	fizz	none	the powder it self is very airy and holey
Vitamin C	grains	white	yes	7	none	clears it	may have a colored tint- green, yellow, pink, orange (if from tablets)
Salt	grains	white	yes	7	fizz	clears it	delayed reaction with iodine (may be difficult to observe)
Sugar	grains	white	yes	7	none	none	like salt but grains are slightly round
Flour	powder	white	no	7	none	blackens it	it's actually off-white
Cornstarch	powder	white	no	7	none	blackens it	pure white, feels slippery
Gelatin	grains	tan	no	7	none	none	gels water
Alka-Seltzer	powder	white	yes	9	fizz	fizz	fizzes with EVERYTHING
Yeast	pellets	tan	no	7	none	none	generally easy to identify
Baking Soda	powder	white	yes	9	fizz	none	rough texture (kinda)
Gypsum	powder	white	no	7	none	none	hardens water

Liquids

Liquid	Color	pH	Scent	Iodine	Notes
Lemon Juice	clear	3	citrus	none	expect pulp
Alcohol	clear	7	alcoholy	none	kinda sweet smelling
Ammonia	clear	9	sweet	none	expect it to be some random color and scent
Vinegar	clear	2	sour	none	very strong scent
Water	clear	7	none	none	nothing special about it
Hydrogen Peroxide	clear	7	none	fizz	delayed reaction

Metals

Metal	Color	Density	Water	HCl	Magnetic	Notes
Aluminum	gray	light	none	fizz	no	delayed reaction with HCl
Copper	copper	heavy	none	none	no	very easy to id
Iron	black	heavy	none	fizz	yes	delayed reaction with HCl
Tin	gray	light	none	little	no	yellow tint
Zinc	gray	heavy	none	fizz	no	shiny
Magnesium	gray	light	little	fizz	no	dull

Chromatography

This is very easy to do. You put a dot of ink on a 6" by 1" piece of white construction paper. Then, get a small cup of water and put the paper on the cup just so that the ink dot is above the water line. Wait for the colors to separate and that's it! You'd be surprised by the difference in black ballpoint pens, magic marker, and dry erase pen.

Fingerprints

Practice identifying and comparing fingerprints it's super easy. There are 3 types of fingerprints(arches, loops,and whorls) they are easily identified by there general shape and number of deltas (triangles made from ridges) arches= a hill shape with no deltas loops= a beanish shape with one delta whorls= a circle like shape with two deltas

Polymers (Not part of 2010 event)

2007-2009 tests ONLY. Polymers are not part of the 2010 event. IMPORTANT TO NOTE!*

These are iffy, sometimes they're in a competition sometimes not but if I remember correctly you have to know PETE,HDPE,PVC,LDPE,PP,PS I think that HDPE,LDPE,and PP float in water while PETE,PVC,and PS do not. This means that the first group has a density less then one and the second group more then one(but to be honest PS AKA Styrofoam was so close to the density of water it floated a couple of times i tested it. To identify the polymers in the first group is easy HDPE and LDPE are translucent while PP is not. HDPE is relatively more translucent then LDPE. Identifying in the second group isn't all that hard either PS will SLOWLY drop down in water or half of the flecks will sink while the other will float. PVC is sometimes rubbery but never transparent while PETE is CLEAR!!!

At the Competition

Once you get your materials and the supervisor starts the competition, start by getting your chromatography paper started. Then, look at the test and see how long you think it will take or how much there is to do. If it is a lot, make sure you split up the work because you don't want to have wasted potential and then not finish. While the is going, identify all the unknowns using tests (see above). Please note that at higher levels of the tournament (state, nationals) different compounds may be combined with each other. For example, flour and Alka-Seltzer. While one person is testing unknowns, the other might want to identify the fiber samples (if there is any). After all the unknowns are identified, read through your packet to learn about the crime scene and answer the questions. Then, after questions have been answered, write out the crime solution essay, discussing how the team chose the culprit(s), based on their motive and supporting evidence (the unknowns the person was carrying compared to the substances found at the crime scene). Following the supervisor's instructions, hand in your papers, clean up your lab area, and relax until the supervisor dismisses you.

Make sure to leave enough time for the essay. Depending on the event, it may be simple or extremely complex; the National supervisor for this year has a tendency to write events with complex essays that require a fair amount of time to write.

WARNING: The rules say you will get 50 minutes however, the 50 includes the supervisor talking to you about safety/tips/rules/etc. so often you will only have 40-45 minutes to work. It is probably a good idea to practice with only 40-45 minutes to get used to competition conditions.