Forensics?

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adam124218
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Re: Forensics?

Postby adam124218 » Wed Jul 02, 2008 4:11 pm

The test isn't always like that. It's only really that way with the national coordinator. Other tests can be totally different. Our regional test had a bunch of questions about interpreting mass spectroscopy, but the state and nationals tests didn't go into that much detail at all. Also, at regionals they gave us these pathetic microscopes, one of which was little better than a hand lens--it's highest magnification must have been about 4x--and the other which had so many dials that even the students who were running the event couldn't figure out how to use it. There's so much variation in what will be on different tests.

Has anyone managed to find pure spandex to test? We've never been able to find it because everything is a spandex blend.

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Re: Forensics?

Postby genes_girl » Wed Jul 02, 2008 5:32 pm

Sorry, I thought it was just in reference to nats. The others vary, but the powder sections tend to stay the same- what is it, how did you identify it, who does it incriminate.

As for the spandex, no, not really. We never really put too much effort into it, we looked up differences between man made vs. organic and other aspects that depending on how they react to flame would narrow it down until we knew what it was.
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Re: Forensics?

Postby Freak of Science » Wed Oct 29, 2008 12:15 pm

In response to the post regarding compounds to be used in a flame test:

I take it that it is necessary to both use a reaction test to determine a carbonate or bicarbonate, as well as a flame test to figure out the metallic compound it is binded to?

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Re: Forensics?

Postby genes_girl » Sat Nov 01, 2008 2:10 am

We never had to use a flame test to identify carbonate vs. bicarbonate and which one it was. You should be able to tell just using HCl and Water. HCL for your reaction test and then water for consistency/dissolves/doesn't dissolve/other and pH.
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Re: Forensics?

Postby adam124218 » Fri Nov 21, 2008 1:26 am

So I was looking at the Chem Lab page on the national website, and I think the picture accompanying it is a picture of Forensics from nationals. I'm pretty sure I'm right. In fact, I'm positive, since I did both of those events at nats and that's definitely Forensics. Can anyone agree with me?

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Re: Forensics?

Postby faraway » Wed Dec 31, 2008 5:37 am

What exactly do we need to know for the chromatography? In my experience you have to the chromatography first or else you'll run out of time..

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Re: Forensics?

Postby iwtban » Wed Dec 31, 2008 5:23 pm

what should you include in the analysis of crime? i think it's important, too cause it's like 20% of the test ( hope i'm right). last year, i always sun out of time to write a good analysis. any suggestion?

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Re: Forensics?

Postby dudeincolorado » Wed Dec 31, 2008 6:12 pm

it's worth 30 this year.....
Ok this is my first year doing this, but i have done crimbusters, and I know in that you need to include: who did it, why they did it, why you choose them, what things incriminate them, who are innocent, why are they innocent, what things relate to them. Make sure you say who did it but ALSO why the other people are innocent. Hope this helps
SO stressed!

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Re: Forensics?

Postby iwtban » Wed Dec 31, 2008 7:05 pm

oh, thanks, that really helps!
i did forensics last year & it has been my favorites; luckily, this year, in the rule book, they clearly state that the judges need to provide a heat source to perform the flame test. invitationals i went last year, they just gave the candles for the flame test which is really ridiculous. and at my state competition, they did not give any candles or anything, even though there were 8 powders.
so, does anyone do the flame test with candles? can you see the red flame when it's LiCl?

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Re: Forensics?

Postby faraway » Wed Dec 31, 2008 11:49 pm

LiCl burns 'carmine red'

What type of instrument would you use to hold the salts in the flame? We used a bacteria scraper :P just something random we found. It worked fine except when we burned a sugar it stuck on the metal...

Also, would you use an electric current to test any of the powders? Some of them when mixed with water have increased conductivity but I really don't think it helps much in identifying.

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Re: Forensics?

Postby genes_girl » Sat Jan 03, 2009 6:37 pm

Let's see here.....

For the final write-up you should include the basics: who did, how you know this, ect. Also why the evidence rules out the other suspects. If there is more than one perpetrator make sure you explain how you know this. So, yeah, basically I agree with dudeincolorado. I tend to subscribe to the more-detailed/more-information/more-facts-is-better theory for this. Not long rambling, but concise with as much support as you can.

For flame tests, my team used nichrome wire and it worked well. There really is no way to avoid sugars caramelizing, you just have to work around it. Cobalt glass can be helpful, but it is up to you. You can really work it either way.

I never used a conductivity tester, we had one in our box but we never used it. You could. It is definitely an option. I recommend a dichotomous key of powders. It works well (especially since you are allowed notes). Just figure out what tests are quickest and will help identify the powders.
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Re: Forensics?

Postby adam124218 » Sun Jan 04, 2009 5:15 am

We use nichrome wire as well. It works well as long as you don't handle it too much.

I've never used a conductivity tester; we've never been able to get it to work. You can get along just fine without one.

As far as chromatography goes, does anyone have any suggestions for the disaster that is sheet chromatography (the kind we get to enjoy at Nationals and at my state competition)? Whenever we do it, it ends up as a total mess (especially the juice). How do you do it well on the tiny sheet of paper?

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Re: Forensics?

Postby 4rensicsKonz » Mon Jan 19, 2009 6:00 pm

genes_girl wrote:Yeah, the tests are somewhere between 130 and 200 questions, plus everything you have to do to find the answers. If you finish it ( and well, not with stupid answers) you are god. We came close once...at regionals. But it is both questions on results AND general information on fingerprints, DNA, etc. Don't forget the writeup as well!

130 to 200 question :shock:
oh dear... at least i can still do crime busters for another year
is it hard? or just long?
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Re: Forensics?

Postby genes_girl » Mon Jan 19, 2009 6:40 pm

It depends on how well you know the material, how fast you run the tests, and how many stupid mistakes you make (because you can't avoid them). Personally, I think it is mainly just long. People who have never been exposed to that form of test before think it is hard and long though. You just have to make sure you are prepared.
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Re: Forensics?

Postby adam124218 » Tue Jan 20, 2009 1:09 am

I would say it's hard because it's long. And because the coordinator is screaming at you the whole time. The tense atmosphere is what makes it really difficult. There are so many questions that mistakes are unavoidable, like I mixed up which solution was which for the polymers at nationals and had to do it again (and I think I messed it up again). Things like that reduce your time and consequently reduce your score.


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