Forensics C

[ckenn4189]

Well, I have looked up what liquid to use and I can't find anything and I am working on flame tests myself but I am asking about pollen because I have never done Forensics before and Crimbesuters had no seeds or pollen. I want to know about other's experiences with seeds on the test.

This is going to be a really helpful resource for you. The density reagents and their respective densities are on that page under polymers. Burn test results can be found pretty easily on Google, though - just google "[name of plastic] flame test" and you can usually find pretty good results.

Seeds and pollen are used very infrequently on tests in my experience - usually it's just matching if something was found on the suspect and at the scene of the crime.

As for addition vs. condensation, it's all about how the polymer forms. Addition is formed when the monomers (units of the molecule) are "added" together, and nothing is released as a result. Adding propylene units together equals polypropylene. In condensation, a by-product such as water or ammonia is formed when the units are formed into a polymer. There are other differences too, but that's the gist of it.

Thank you so much!

[ckenn4189]

Would the density of a certain plastic be relative in any liquid? For example, if the density was 1.2 in water, would it also be 1.2 in, say, corn oil?

[SilverBreeze]

Would the density of a certain plastic be relative in any liquid? For example, if the density was 1.2 in water, would it also be 1.2 in, say, corn oil?

Yes. Density is mass over volume and is conserved for most solids under typical lab conditions.

[ckenn4189]

What sort of questions are asked when it comes to glass analysis? Also, will we need to calculate the refraction index or will it be provided for us?
Thanks!

[SilverBreeze]

What sort of questions are asked when it comes to glass analysis? Also, will we need to calculate the refraction index or will it be provided for us?
Thanks!

scioly.org has a lot of practice tests submitted by users that can be found here: https://scioly.org/tests/
I recommend going through some of them to see what types of questions are asked.

[Limke]

What sort of questions are asked when it comes to glass analysis? Also, will we need to calculate the refraction index or will it be provided for us?
Thanks!

Typically, for glass analysis, you should know Snell's Law which allows you to calculate refraction indexes/angles of refraction
Also, know the general physics behind refraction (both quantum/classical). It does not need to be super in-depth, but you should have a general understanding.
You should also know how to analyze types of glass fractures (ie. which fracture occurred first? what are the two major types of fractures? what side do fractures occur on relative to impact? etc.)

[ckenn4189]

Thanks for the help on glass analysis! Also, how do I measure Rf on paper chromatography? I may have set this up wrong but whatever.
Image: https://drive.google.com/file/d/1w9AaVZ ... sp=sharing

[ckenn4189]

Please disregard that last post, it won't let me delete it. In terms of glass, the rules say "be able to determine the type of glass found at the crime scene" using a refractive index. What types of glass are normally used? Lastly, how often are you asked to do TLC?

[Limke]

Please disregard that last post, it won't let me delete it. In terms of glass, the rules say "be able to determine the type of glass found at the crime scene" using a refractive index. What types of glass are normally used? Lastly, how often are you asked to do TLC?

Typical glasses are crown glasses, pyrex, fused silica, etc. You should be able to find a list online with common glasses and their refractive indexes.
https://www.physlink.com/reference/indi ... action.cfm

I've only ever had to do TLC twice (once at States last year in PA but we were guided through it) and once at nationals (we were largely on our own for this one). Because of resources and stuff, I've never done TLC at an invitational before, but I would recommend investing in supplies to try it out so that you are familiar with the process. There are a lot of supplemental questions about TLC though (ie. stationary/mobile phase, uses, pros/cons, etc.)

https://www.chemguide.co.uk/analysis/ch ... layer.html

[ckenn4189]

Well, thanks for all of your help but my tournament got canceled. Oof