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Science Crime Busters Test Exchange 2015

Teams will identify the perpetrators of a crime or crimes by using paper chromatography and analysis of unknown solids, liquids, and plastics found at the scene of a crime.

What are some of the tests that I need to know how to do for powders?

The tests are so that you can identify the different powders, so it is really up to you for which tests you want to run. I do distilled water (Ph and solubility), Iodine, and HCI. I also look at the appearance of the powder, but powders can look different depending on where you get them from so you don't want to rely on just appearance.

thanks for the list guys. it'll really help me.

How do you figure out mixtures

[Morgan] wrote:How do you figure out mixtures

First of all, there are 3 nonmetals which can never be mixed in this event: yeast, vitamin C, and sodium acetate. That being said, everything left is neutral or basic and non-biological.

The key to finding the components to a mixture is to react each off individually. If there appears to be a powder and a crystalline component, add HCl or iodine to a sample. If the iodine turns blue, finding the first component will be straightforward because you will only need to find the pH of the mixture with water. A more neutral pH will mean that it's flour; a more basic pH will mean cornstarch. If the iodine fizzes (and the HCl), then you have Alka-Seltzer. A fizz with only the HCl means the component is either CaCO3 or NaHCO3. Once again, a pH test will show the difference: a neutral pH means calcium carbonate, and a basic pH means baking soda. No reaction means gypsum. To find the crystal, test for solubility. Sand will not dissolve, whereas salt and sugar will. The difference between the latter two is that salt has cubic crystals, and sugar has irregular crystals.

Two crystals is fairly easy because you can skip the HCl and iodine and go straight for solubility. Once again, a component that does not dissolve is sand, and a component that does is either salt or sugar, which can be differentiated by crystal shape. If both dissolve, you have salt and sugar (probably the single most common mixture in this event).

For two powders, test with iodine first, then HCl if not all of the mixture fizzed or turned blue, and finally pH if needed. Go off of the information above to find each, and use logic if two things react at once.

Hope this helps!

My partner and I are having trouble distinguishing between dog hair and human hair. We know the difference in comparison to the other, but when given a microscope slide at competition we always get it wrong . What are the best ways to identify the types of hair? (please include cat for good measure)

So in my state you can bring in a binder of information, and there are no guidelines about how big it can be. I feel like this is making the event to easy. Is it like this in all the states? If so how many pages of info are you guys planning to bring?

Panda Weasley wrote:So in my state you can bring in a binder of information, and there are no guidelines about how big it can be. I feel like this is making the event to easy. Is it like this in all the states? If so how many pages of info are you guys planning to bring?

Yes, that is a national guideline according to this year's rules. I am not letting my teams bring much- as in an old cheat sheet and about a half inch binder of stuff- because I have learned that too much reference material slows you down.

Also, ditto for Forensics.