Forensics C

YungMihi
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Re: Forensics C

Postby YungMihi » Mon Apr 09, 2018 8:31 pm

Hey anyone have any good resources for soil id, pollen, and ento? These topics haven't really come up in the states or regionals tests but I feel like they will at Nats.

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Re: Forensics C

Postby ET2020 » Mon Apr 16, 2018 6:44 pm

Can someone please clarify what concentrations of liquids will be used? The rules just say "10% NaCl, 46% isopropyl alcohol" etc without specifying whether it is percent by mass or volume. Also many of the old nationals test provide solution concentration and density, but their numbers don't make sense to me. For example one test says "46% isopropyl alcohol: 0.95 g/cm^3). The problem is that 46% iso by mass has a density of 0.88, while by volume has a density of 0.90. Does anybody know if we can get clarification on this?
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pikachu4919
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Re: Forensics C

Postby pikachu4919 » Mon Apr 16, 2018 7:06 pm

YungMihi wrote:Hey anyone have any good resources for soil id, pollen, and ento? These topics haven't really come up in the states or regionals tests but I feel like they will at Nats.


The wiki is a good start, and so is this (it's the national supervisor's website). From there, you could expand your own search, as that's a much more effective way to learn.

ET2020 wrote:Can someone please clarify what concentrations of liquids will be used? The rules just say "10% NaCl, 46% isopropyl alcohol" etc without specifying whether it is percent by mass or volume. Also many of the old nationals test provide solution concentration and density, but their numbers don't make sense to me. For example one test says "46% isopropyl alcohol: 0.95 g/cm^3). The problem is that 46% iso by mass has a density of 0.88, while by volume has a density of 0.90. Does anybody know if we can get clarification on this?


The recipes for those solutions are actually found here, and having used this before, I know for sure that it is not percent by mass lol. I'm not sure what system that's based on, but it is literally the national supervisor's recipes, so doesn't hurt to follow it, I guess.
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Re: Forensics C

Postby potatosoup9000 » Tue May 08, 2018 11:51 pm

Does anyone know how Snell's law/index of refraction calculations were done at nationals? The seniors from our team never did them. Were they done normally, like shinning a laser through a flat sample, or do you have to do extra math for the spherical shape of the sample?
Thanks!


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