Forensics C

[pikachu4919]

Forensics C: Given a scenario and some possible suspects, participants will perform a series of tests which along with other evidence or test results will be used to solve a crime.

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[CPScienceDude]

So on Woz's website, she uses the smell of burning wool and silk to differentiate them. My problem is that she wrote that burning silk smells like burning meat? And I know smells are subjective, but what are your guys' takes? Idk, it just seems off to me that it would smell like burning meat. Besides smell, what is another way to tell them apart besides looking under a microscope (if one isn't available)?

Edit: Also, what are some good resources on mass specs? I have no idea how to read them, much less name the compound that it represents. Any help is appreciated, as I'm at a standstill right now.

[wec01]

So on Woz's website, she uses the smell of burning wool and silk to differentiate them. My problem is that she wrote that burning silk smells like burning meat? And I know smells are subjective, but what are your guys' takes? Idk, it just seems off to me that it would smell like burning meat. Besides smell, what is another way to tell them apart besides looking under a microscope (if one isn't available)?

Edit: Also, what are some good resources on mass specs? I have no idea how to read them, much less name the compound that it represents. Any help is appreciated, as I'm at a standstill right now.

Yeah silk didn’t smell like burning meat to me. For me the easiest way to identify silk was that it would turn into an ashy ball during the burn test. The only one with an extremely obvious smell is wool, the rest we largely just identified by what they looked like while/after burning.

As for mass specs they’re a little complicated to figure out and theoretically you should only be given somewhat small compounds like ethane as larger ones get increasingly more complex to identify. I would look into learning some basic organic chemistry, particularly nomenclature and functional groups, and keep a list of the masses of common groups (There is a nice graphic online somewhere with common groups that break off in mass specs) and molecules on your cheat sheet. Even if you can’t identify the molecule though, just understanding what the peaks represent, how to interpret the axes, and general terminology should get you most of the points.

Edit: here is the graphic I mentioned
https://i1.wp.com/www.compoundchem.com/ ... gments.png

Edit: here is also a good link for understanding mass specs
https://www.chemguide.co.uk/analysis/ma ... u.html#top

[pikachu4919]

So on Woz's website, she uses the smell of burning wool and silk to differentiate them. My problem is that she wrote that burning silk smells like burning meat? And I know smells are subjective, but what are your guys' takes? Idk, it just seems off to me that it would smell like burning meat. Besides smell, what is another way to tell them apart besides looking under a microscope (if one isn't available)?

Edit: Also, what are some good resources on mass specs? I have no idea how to read them, much less name the compound that it represents. Any help is appreciated, as I'm at a standstill right now.

Yeah silk didn’t smell like burning meat to me. For me the easiest way to identify silk was that it would turn into an ashy ball during the burn test. The only one with an extremely obvious smell is wool, the rest we largely just identified by what they looked like while/after burning.

As for mass specs they’re a little complicated to figure out and theoretically you should only be given somewhat small compounds like ethane as larger ones get increasingly more complex to identify. I would look into learning some basic organic chemistry, particularly nomenclature and functional groups, and keep a list of the masses of common groups (There is a nice graphic online somewhere with common groups that break off in mass specs) and molecules on your cheat sheet. Even if you can’t identify the molecule though, just understanding what the peaks represent, how to interpret the axes, and general terminology should get you most of the points.

Edit: here is the graphic I mentioned
https://i1.wp.com/www.compoundchem.com/ ... gments.png

Edit: here is also a good link for understanding mass specs
https://www.chemguide.co.uk/analysis/ma ... u.html#top

With tests by the national supervisor (@CPS that also applies to you since she does Indiana tournaments due to being from there), it’s even more basic than that - you almost literally only have to identify the m/z values of the M+ peak, the base peak, and the smallest peak, and you have to be able to match the scene mass spec to a suspect. She doesn’t even go into the nitty gritty stuff of identifying the molecules themselves based off the mass spec. I would say you would probably want to know that for other tournaments though, since they might ask you about that.

As for fibers, I think a combination of their appearance to the naked eye and their burn test (smells don’t necessarily need to be involved) might be fine if you practice enough with the actual samples themselves and make your own observations, it registers more powerfully then reading literature about it since everyone’s perception of something related to senses especially varies a lot (like I could tell you that I think burning silk smells like burning sugar and you might find that strange but if it works for you every time and that’s how you sense that smell, then you should go with your notion of the observation since your senses are yours and not anyone else’s).

[febflower]

Are there any online stores where my school can buy plastic and fiber samples?

[CPScienceDude]

Are there any online stores where my school can buy plastic and fiber samples?

I think the North Carolina Scioly website has some. They are frequently out of stock though.

[wec01]

Are there any online stores where my school can buy plastic and fiber samples?

I think the North Carolina Scioly website has some. They are frequently out of stock though.

You can also start collecting your own samples from old clothes and plastic containers.

[Nerdforlife]

What all do we need to know for this event?

[c21k]

What all do we need to know for this event?

The rules manual is a good place to start, as is the scioly.org page for forensics: https://scioly.org/wiki/index.php/Forensics

[ledwards003]

I was wondering how in-depth I should go when it comes to the powders/crystals. I assume I have to know how they react with different chemicals, the flame tests, what they can be found in, and their chemical formulas. How far should I go after that? Is there anything specific I should know about them?