Forensics C

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pikachu4919
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Re: Forensics C

Post by pikachu4919 »

c21k wrote:
olhs4n6 wrote:
LostInTheSauce wrote:
Guessing you went to the Solon Invitational?

The Solon Invitational forensics was absolutely insane. My partner's first time doing it, so I had her literally just read and make lists of the suspects/what would implicate them. That alone took her 10 minutes (but she did find a bonus at the end of the instructions). We were lost at what to do with the plastics so I just put them in water and guessed from there... yikes... At least we got the person right. Any tips for how to divide/conquer better at regionals?
Wow, what a way to start! Props to your partner for surviving it and living to tell the tale ;) For the division of material, my partner and I split the qualitative analysis. Then we assign other material based on our strengths. The leftovers we both study so that whoever finishes their section of the test can just do those parts. I also find that allotting time for specific areas of the test can be helpful for pacing purposes.
Hi um, I was one of the three writers of that test, and unfortunately, none of us were actually able to be there to proctor it. Now that I think about it, I realize we forgot to tell the person who was proctoring it (who was doing so for the first time ever) to make those density solutions. That's our fault, and we thoroughly apologize for it.

As for tackling the test, that test is actually a baby version of the one that my co-ES at MIT and I wrote for the 2019 MIT Invite (he was also one of the other two writers), and I'll say that the way you split is entirely dependent on what you and your partner each are comfortable with. For example, if someone can do powders really well and can't do polymers while the other person can do polymers really well yet can't do powders very well, then you can obviously definitely split that way. Or if one person is super comfortable with both parts of ID while one person doesn't, then you can have that person do all ID's and then the other person focuses solely on the crime/free response. Again, I can't comment on any one pair's synergy, so that's up to you to decide. But total trust in your partner is a must - if you want to finish the test, you absolutely will not have time to check over your partner's work, and you have to trust that they knew what they were doing. Some things for sure are that I would advise starting the chromatography right when the time starts and leaving ~20mins solely for the crime analysis, and at that time, your partner can either finish the rest of the ID's and/or tackle the free response and not start cleanup until 5 mins before time. That's how I would ideally approach it, but it does take quite a bit of skill to pull it off.

If this says anything, a couple lucky competitors got to start their forensics careers with my other partial brainchild in the 2019 MIT Forensics test...
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Re: Forensics C

Post by Qu€€nMon€y »

olhs4n6 wrote:
LostInTheSauce wrote:
c21k wrote:Does anyone have some advice on how to identify a given plastic sample?

(no burn tests permitted, no solutions of different densities or indices provided)
Guessing you went to the Solon Invitational?

The Solon Invitational forensics was absolutely insane. My partner's first time doing it, so I had her literally just read and make lists of the suspects/what would implicate them. That alone took her 10 minutes (but she did find a bonus at the end of the instructions). We were lost at what to do with the plastics so I just put them in water and guessed from there... yikes... At least we got the person right. Any tips for how to divide/conquer better at regionals?

Wait one question: How did you differentiate the plastics with water? When I practiced the plastics, all the plastics floated. Does anyone have notes on plastics that could be useful?
Medal count: 1 :(
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Re: Forensics C

Post by olhs4n6 »

Qu€€nMon€y wrote:
olhs4n6 wrote:
LostInTheSauce wrote:
Guessing you went to the Solon Invitational?

The Solon Invitational forensics was absolutely insane. My partner's first time doing it, so I had her literally just read and make lists of the suspects/what would implicate them. That alone took her 10 minutes (but she did find a bonus at the end of the instructions). We were lost at what to do with the plastics so I just put them in water and guessed from there... yikes... At least we got the person right. Any tips for how to divide/conquer better at regionals?

Wait one question: How did you differentiate the plastics with water? When I practiced the plastics, all the plastics floated. Does anyone have notes on plastics that could be useful?
You would usually need more than one liquid (corn oil, isopropyl alcohol, water, salt-water, etc) to be able to differentiate solely based on density. I would practice plastics again, only PP, LDPE, and HDPE should float in water, though I could be wrong. My plastics info just came from the wiki at https://scioly.org/wiki/index.php/Forensics (someone else can back me up on the water thing though)
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Re: Forensics C

Post by c21k »

olhs4n6 wrote:
Qu€€nMon€y wrote:
olhs4n6 wrote:

The Solon Invitational forensics was absolutely insane. My partner's first time doing it, so I had her literally just read and make lists of the suspects/what would implicate them. That alone took her 10 minutes (but she did find a bonus at the end of the instructions). We were lost at what to do with the plastics so I just put them in water and guessed from there... yikes... At least we got the person right. Any tips for how to divide/conquer better at regionals?

Wait one question: How did you differentiate the plastics with water? When I practiced the plastics, all the plastics floated. Does anyone have notes on plastics that could be useful?
You would usually need more than one liquid (corn oil, isopropyl alcohol, water, salt-water, etc) to be able to differentiate solely based on density. I would practice plastics again, only PP, LDPE, and HDPE should float in water, though I could be wrong. My plastics info just came from the wiki at https://scioly.org/wiki/index.php/Forensics (someone else can back me up on the water thing though)
I am in concurrence with olhs4n6. The density of water is about 1 g/ml while PP, LDPE, and HDPE have densities higher than 1 g/ml. Make sure that if you do practice with water, that it is deionized/distilled water. I don't know if tap water has enough contaminants that it would alter the density that significantly, but seeing as all the plastics floated on your last trial, it wouldn't hurt.
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Re: Forensics C

Post by Qu€€nMon€y »

So at the cornell invitational bunsen burners didn't work so we had candles instead which I didn't understand how to ID powders without a bunsen burner. Any tips on identifying powders without flame test?
Medal count: 1 :(
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Re: Forensics C

Post by C8H10N4O2! »

Qu€€nMon€y wrote:So at the cornell invitational bunsen burners didn't work so we had candles instead which I didn't understand how to ID powders without a bunsen burner. Any tips on identifying powders without flame test?
I ran into this problem too. I narrowed down some of them, but then got stuck. I think I was able to guess correctly on a one or two of them, just by recognizing the shape of the powders from practising, but other than that, I had no idea.
I personally was extremely disappointed with the cornell forensics test overall. The actual questions were way too easy, and the one real lab part (powders) was missing several parts (no gas for bunsen burners, no benedicts, and the KI solutions was cloudy and old). I wish they wouldve at least given the pictures of the flame tests or the flame test results. I know this would make it easier for teams that have not practiced, but the test asked such easy questions to begin with, I feel as though the difference between placing and not was who guessed the identity of the powders the best.
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Re: Forensics C

Post by Qu€€nMon€y »

C8H10N4O2! wrote:
Qu€€nMon€y wrote:So at the cornell invitational bunsen burners didn't work so we had candles instead which I didn't understand how to ID powders without a bunsen burner. Any tips on identifying powders without flame test?
I ran into this problem too. I narrowed down some of them, but then got stuck. I think I was able to guess correctly on a one or two of them, just by recognizing the shape of the powders from practising, but other than that, I had no idea.
I personally was extremely disappointed with the cornell forensics test overall. The actual questions were way too easy, and the one real lab part (powders) was missing several parts (no gas for bunsen burners, no benedicts, and the KI solutions was cloudy and old). I wish they wouldve at least given the pictures of the flame tests or the flame test results. I know this would make it easier for teams that have not practiced, but the test asked such easy questions to begin with, I feel as though the difference between placing and not was who guessed the identity of the powders the best.

The test was easy but since I didn't get the identity of the powders I didn't know what to do for the analysis and ending up getting 29th and I normally don't do that bad like for westlake I got 10th and Duke got 9th.
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Re: Forensics C

Post by JJC28 »

How much can you rely on the appearance of the powder for the purpose of identifying it?
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Re: Forensics C

Post by Qu€€nMon€y »

Does anyone know how to do mass spec questions like these?:

What fragmentation group does the peak at m/z=31 represent?
The loss of which small functional molecule is represented at m/z=28?
What is the identity of the molecule represented in this mass spectrum?

I understand that you can't see the mass spec but I would like to know how to do these questions in general
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Re: Forensics C

Post by olhs4n6 »

JJC28 wrote:How much can you rely on the appearance of the powder for the purpose of identifying it?
I usually only use the appearance as a last resort to narrowing down. Lets say there are 2 with a yellow flame test, and they have the same solubility, etc. then I would go to the appearance...
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