Crime Busters

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. Lastly, students should be able to use this data to answer some questions about who committed the crime and how the evidence supports their argument.

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. If lab aprons, make sure you're wearing long sleeves.
 * Also, make sure you have closed toe shoes, NO sandals
 * 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 notes on anything involved with the event! Only one sheet of notes (typed or handwritten) 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 container of water, an eye dropper, and chromatography materials, in addition to your testing kit.

Make a chart for testing. For powders, include color, reactions with water, HCl, and Iodine; odor (distinct, faint, or none); shape (crystalline, granular, or powder), solubility (whether it dissolves in water or not), and reaction to pH or Litmus paper. For metals, include reactions to 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.

Liquids
Each liquids has a "give-away", making them fairly easy to identify-
 * Lemon Juice has a strong lemony odor (and is a strong acid, like vinegar)
 * Ammonia is the only strong base
 * It is best to use pH paper first, before smelling the unknown liquid, so that you will never have to smell ammonia (even if by wafting) since it can be chosen conclusively if the unknown liquid has a very basic pH.
 * Vinegar has a distinctive vinegar odor (and is a strong acid, like lemon juice)
 * Rubbing Alcohal is neutral, but has a distinctive odor
 * Hydrogen Peroxide and water are very similar (both are odorless, neutral liquids), but there is a simple way to tell them apart. Fill a small well in your testing tray with the liquid, put in a few drops of iodine and stir. After about a minute (though sometimes more), tons of bubbles will appear if it is hydrogen peroxide, while nothing will happen in water (besides the color change due to iodine's color).

Metals
Almost every metal has a "give-away", making them fairly easy to identify-
 * Iron is the only magnetic metal
 * Copper is the only metal with a color other than grey (or similar).
 * Magnesium will often steam with HCl, and will also let off a strong odor when HCl is added.
 * Zinc will react vigorously (but will not steam) with HCl, and is non-magnetic.
 * Tin and aluminum are very similar (neither react very much with HCl), but there are a few things that can be done to tell them apart. First, tin often has a yellowish tint, which aluminum will never have. Next, tin is often fairly shiny, while aluminum is dull. Lastly, if the metal is very malleable, it is probably aluminum (think aluminum foil).

Water Testing
The rules describing water testing are very vague. They only specify what can be tested for, but not how they can be tested. Titrations, probes, and colored strips are some possible methods used. Below is a table of the very basics on each of the things that they can ask about and have you test for-

Examples of Water Testing on Past Tests
2010 Southeast Pennsylvania Regionals- A few strips were given, very similar to pH paper, that you just dipped in and compared to a chart that they provided. You then had to match you data (the crime scene liquid) to data provided for the liquids that the suspects were carrying (their water bottles) and say which it came from. There were 4 strips (so 4 tests total), similar to these- http://www.omega.com/pptst/WTS_Series.html. All in all, it wouldn't take you more than 5 minutes max.

2010 Pennsylvania States- Four liquids were given at a shared station, and you had to do two tests on each: pH and some sort of titration (so 8 tests total). For the pH portion, I think it was done using indicator dyes, though I have almost no clue, because they said we could use pH paper instead if we wanted. As far as the titration, they had someone there to explain how to do it, and written instructions. You filled a container with the liquid, then added a certain number of drops of an indicator and a certain number of drops of another chemical, mixing continuously. You then had a tiny syringe filled with another chemical and you slowly added it, mixing constantly until the solution turned purple (it was pink beforehand). I was terrible at this, so it took me around 20 minutes, but you could probably have done it in 10 if you had done a titration before (I would recommend practicing this at least once, because it seems like something that they give at a fair number of competitions).

2010 Nationals- Basically, you got four probes (conductivity, DO, pH, and temperature) and a TI graphing calculator (already set up to receive and display information from any probe if you plugged it in. No preparation was needed to understand how it worked, since they gave written and verbal instructions). You then had an observation/conclusion sheet to record information. You wrote down the probe used and the numerical value received (0.5 points for each one of these pairs) and then had a line to write a conclusion based on the information (0.5 points for each of these). To get full credit (5 points), you needed 5 data entries and 5 conclusions based off those entries. Here is what we had (I don't remember the numbers)-

DO- ### (low)- There is very little dissolved oxygen in the liquid

Temperature- ### (room temp.)- The liquid is about room temperature

Conductivity- ### (high)- The liquid conducts electricity very strongly

pH- ##.# (high)- The liquid is very basic

Temperature- ### (same as first entry)- the liquid does not change temperature over time
 * I'm not sure if the last one was what they wanted, but there were only 4 probes and you needed 5 tests, so we put that down.

On the crime part of the test, they said "Liquid S (the one you tested) was found around the area of a freezer, dishwasher, and sink (or something to this extent). Do the necessary tests to figure out exactly where it came from". Since it was very basic and a strong conductor, we said it was from the freezing coils in the freezer (again, I don't know for sure if that's right). They didn't ask any supplemental questions about water testing, like they do for the powders, liquids, fingerprinting, DNA, etc.

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! Once you have taken the paper out, quickly put a line in pencil where the top edge of the water is on the paper. This allows you to find the Rf (retention factor) value of any ink spot if they ask, ot they might be looking for it for full credit.

Fingerprints
Practice identifying and comparing fingerprints. There are 3 basic categories of fingerprints(arches, loops,and whorls). They are easily identified by there general shape and number of deltas (triangles made from ridges). Make sure you know if your event supervisor is looking for the basic type (loop, arch, whorl), or the more in-depth name (Tented Arch, Ulnar Loop, etc.).
 * Arches= a hill shape with no deltas
 * Tented arch= an arch with a sharp corner at the top point
 * Plain arch= an arch with a more rounded top point
 * Loops= a beanish shape with one delta
 * Ulnar Loop= A loop pointing towards the pinky
 * Radial Loop= A loop pointing towards the thumb
 * Whorls= a circle like shape with two deltas
 * There are many sub-categories of whorls, such as (but not limited to) tracings, accidental whorls, or double loops. It is highly unlikely that they will ask for one of these, so this should be the last thing you should worry about learning. However, the most important whorls to know are the plain whorl and double loop.

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

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 do the water testing (If there is water testing at a common station, make sure you go there first, because it will get crowded near the end, and you may have to wate time waiting). 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. At 2010 Nationals, 45 minutes were given to work, along with a 5 or 10 minute clean-up time afterwards.

Scoring
The scoring is composed of these elements:


 * Unknowns Identification (50% of total score)


 * Chromatography (5%)


 * Crime Solution Essay (25%) (tiebreaker)


 * Water Testing (10%)


 * DNA, finger printing, tire treads, finger prints, shoe prints (10%)

Practice Tests
[[Media:SCB Test.pdf|"Dwisney Stars-Twenty Years Later" Test]]
 * Note: You will need to print off the fingerprints, shoeprints, and DNA yourself.

[[Media:Answer Key.pdf|"Dwisney Stars-Twenty Years Later" Answer Key]]

[[Media:SCBtest3.pdf|2009 Northridge Invitational Test]]

[[Media:SCBanswers.pdf| 2009 Northridge Invitational Answers]]

Science Crimebusters Quiz

2007 Science Crimebusters Exams