samlan16 wrote:Opinions on the binder? I'm surprised they upgraded us from a sheet, but it will probably make Forensics a ton harder.
jdjmoon wrote:Does anyone have good site for Mass Spectroscopy? I had one, but now it is unavailable, so I cannot get any good informations on it.
byi wrote:CAN ANYONE HELP ME WITH A FORENSICS ASSIGNMENT?
elizagabito wrote:I need help... I don't know anything that deals with chemistry so I basically don't know anything about this event... Any suggestions on what to study first? Like what are good sites & techniques on studying.
Azismith wrote:I was wondering -- does anyone have a good way (other than the super-subjective 'which bends easier? which scratches easier?) to differentiate between PC and PMMA? Thanks!
samlan16 wrote:Azismith wrote:I was wondering -- does anyone have a good way (other than the super-subjective 'which bends easier? which scratches easier?) to differentiate between PC and PMMA? Thanks!
Density. PC is somewhere between 1.2 and 1.6 g/mL, but PMMA is around 1.16 g/mL. If you are incredibly lucky, they will give you corn syrup to test this in. PMMA floats; PC sinks.
sciencegeek999 wrote:Hey guys, I got put in this event, and I've never done it before. Other than the rules, what should I know about it to start off? How do I prepare for it? Thanks in advance.
salcedam wrote:What I would recommend is starting right off the bat with learning how to identify the powders since that's a major chunk of the test and subsequently, one of the more important parts of it. For powders, you should have some sort of flowchart in place so as you can sequentially go through different tests (such as solubility, flame colors, HCl reactions, etc.) until you can identify it. For example, to identify boric acid, the only test you need to do for that is to do a flame test because boric acid makes a green flame. LiCl gives off a red flame and KCl gives off a purple flame. Those are the only three powders that will give those distinctive colors. The others will either give you a yellow, orange-ish, or no flame color at all. That's when you need to continue with the next step which would be to determine solubility and so on and so forth.
Then once you have powders down or at least have an idea of how to do them, move to the fibers and plastics and learning to identify those using burn tests (for the fibers in particular since they usually won't allow burn tests for plastics). For plastics, you identify them using densities so you need a flowchart just like for the powders of what to do when one plastic sinks in one solution. So let's say you have a plastic that sinks in water. You know that it must have a higher density so then you test the density using salt water. Different competitions will give different concentrations so you should know the densities of the various concentrations of salt water so that when they give you, let's say, a 10% salt solution and it sinks, you know that it must have a density higher than 1.074 g/mL since that's the density of a 10% salt solution. Then you should test the plastic using corn syrup or some high density liquid to see if it floats or sinks. If it sinks in corn syrup, it has to be PVC (according to the flowchart I've made) and if it floats, it's PETE.
So basically, you need to research flowcharts on powders and plastics as well as learn specific characteristics of fibers such as how they react when burned and how they look. From powders, fibers, and plastics, you move on to everything else. I'd focus less on glass and dirt/tire tracks and such since that's mostly matching. Most tests that I've come across focus mainly on blood, fingerprints, reading mass spec, and the occasional entomology question. When studying those things, you don't need to get too in-depth, but you should go past the surface a little bit. I've had tests where they ask how fingerprints are formed, how many ridges a fingerprint has, things besides matching and identifying fingerprint types. Hope that helps somewhat!
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