Forensics C

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Forensics C

Postby Jim_R » August 14th, 2012, 7:04 pm

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Re: Forensics C

Postby smartgirl12 » September 29th, 2012, 12:25 pm

How do you figure out Mass Spectra? I've tried to search it up on google but nothing comes up. I am hopelessly confused. :?
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Re: Forensics C

Postby computergeek3 » September 30th, 2012, 9:22 am

How do you figure out Mass Spectra? I've tried to search it up on google but nothing comes up. I am hopelessly confused. :?
As are the rest of us. What I gather from reading in an AP Chem book is that if you're analyzing ONE element, the highest peak will be the most abundant isotope.

http://www.chemguide.co.uk/analysis/mas ... ments.html is a good website
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Re: Forensics C

Postby Skink » October 3rd, 2012, 8:06 am

If that link isn't enough, I'd suggest loaning or ordering yourself a textbook. Unless you have specific questions...

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Re: Forensics C

Postby Jtim-15 » October 21st, 2012, 6:46 am

Does anyone have any suggestions for how to study for this event first time? I competed last year as a freshman, placed 6th in astronomy/astrophysics and 10th in dynamic planet, both with my scheduled partner missing and a very unhelpful fill-in in his place.

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Re: Forensics C

Postby EastStroudsburg13 » October 21st, 2012, 7:29 am

I actually asked that question last year, since our team had struggled in Forensics in the past. It was pretty helpful as a starting point, even though I only competed in Forensics once personally. Here's what he said:
What I would recommend is starting right off the bat with learning how to identify the powders since that's a major chunk of the test and subsequently, one of the more important parts of it. For powders, you should have some sort of flowchart in place so as you can sequentially go through different tests (such as solubility, flame colors, HCl reactions, etc.) until you can identify it. For example, to identify boric acid, the only test you need to do for that is to do a flame test because boric acid makes a green flame. LiCl gives off a red flame and KCl gives off a purple flame. Those are the only three powders that will give those distinctive colors. The others will either give you a yellow, orange-ish, or no flame color at all. That's when you need to continue with the next step which would be to determine solubility and so on and so forth.

Then once you have powders down or at least have an idea of how to do them, move to the fibers and plastics and learning to identify those using burn tests (for the fibers in particular since they usually won't allow burn tests for plastics). For plastics, you identify them using densities so you need a flowchart just like for the powders of what to do when one plastic sinks in one solution. So let's say you have a plastic that sinks in water. You know that it must have a higher density so then you test the density using salt water. Different competitions will give different concentrations so you should know the densities of the various concentrations of salt water so that when they give you, let's say, a 10% salt solution and it sinks, you know that it must have a density higher than 1.074 g/mL since that's the density of a 10% salt solution. Then you should test the plastic using corn syrup or some high density liquid to see if it floats or sinks. If it sinks in corn syrup, it has to be PVC (according to the flowchart I've made) and if it floats, it's PETE.

So basically, you need to research flowcharts on powders and plastics as well as learn specific characteristics of fibers such as how they react when burned and how they look. From powders, fibers, and plastics, you move on to everything else. I'd focus less on glass and dirt/tire tracks and such since that's mostly matching. Most tests that I've come across focus mainly on blood, fingerprints, reading mass spec, and the occasional entomology question. When studying those things, you don't need to get too in-depth, but you should go past the surface a little bit. I've had tests where they ask how fingerprints are formed, how many ridges a fingerprint has, things besides matching and identifying fingerprint types. Hope that helps somewhat!
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Re: Forensics C

Postby Jtim-15 » October 23rd, 2012, 6:11 pm

Thanks a lot, that we really help get me started. Our big guy graduated last year and he wanted me to do forensics for him, but I never really asked where to start.

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Re: Forensics C

Postby Geezer » October 30th, 2012, 6:02 pm

Where are you guys getting your materials from. Did you ask your high school chem teachers or did you go out of your way to buy them from the two kits they are selling or are you just asking your high school teachers for the materials and then scavenging the rest from various places. If so, where are you getting your polymers from?

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Re: Forensics C

Postby scm424 » November 2nd, 2012, 8:28 am

Is the forensics DVD offered on the sonic website helpful at all?

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Re: Forensics C

Postby LMayeski84 » November 13th, 2012, 10:16 am

How are you doing the flame test for calcium nitrate?


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