Forensics C

[Phenylethylamine]

How about soil analysis? Anyone have a site I can go to for that?

In my experience, soil analysis has been mostly common sense: this suspect is a beach lifeguard, and very sandy soil was found at the crime scene, so that implicates him. Potting soil was found at the crime scene, and this one works in a greenhouse. Things like that.

On some events, they might conceivably ask you questions about soil classification itself; I'd put a soil texture triangle in your notes if you have room. But really, I don't think I've ever seen soil used on any event in more than a simple common-sense way.

[NinjaChicken]

In my experience, soil analysis has been mostly common sense: this suspect is a beach lifeguard, and very sandy soil was found at the crime scene, so that implicates him. Potting soil was found at the crime scene, and this one works in a greenhouse. Things like that.

On some events, they might conceivably ask you questions about soil classification itself; I'd put a soil texture triangle in your notes if you have room. But really, I don't think I've ever seen soil used on any event in more than a simple common-sense way.

Thanks, that image is perfect. I have plenty of space on my notes, and that was basically the only part in our last invite that I didn't really know that was on the test.

[Dragonshark]

I haven't had much hands-on experience with this event, and Regionals is in a few days >_<. My partner is going to do qualitative analysis, while I do polymers/fibers, some of the crime scene evidence, and the essay. Is it generally a good idea that we start the chromatogram early in the test and write a portion of the essay as soon as we're finished analyzing a piece of evidence?

Edit: (apologize for all of these questions) How can you tell the difference between sodium bicarbonate and carbonate? (as in, what test should you perform?)
Edit 2: Actually, forget about the above edit. Figured it out.

[salcedam]

I haven't had much hands-on experience with this event, and Regionals is in a few days >_<. My partner is going to do qualitative analysis, while I do polymers/fibers, some of the crime scene evidence, and the essay. Is it generally a good idea that we start the chromatogram early in the test and write a portion of the essay as soon as we're finished analyzing a piece of evidence?

Edit: (apologize for all of these questions) How can you tell the difference between sodium bicarbonate and carbonate? (as in, what test should you perform?)
Edit 2: Actually, forget about the above edit. Figured it out.

You should definitely start doing chromatography right away so the eluent has time to move the ink molecules up far enough that you can get a good reading on Rf values and such. In terms of the essay, it depends on how fast and how thorough you can be. The way I do essays is, as I mentioned in some post in here before, I write down the names of EVERYONE and next to each person, I write down the things that matched. That gives me a good portion of the points. Then afterwards, if there's time, I write an analysis/conclusion to the essay that states who the suspect is and why. But you should, at the bare minimum, have written everything down that matches each person because the proctor will give you points on the fact that you wrote things down.

[Dragonshark]

I haven't had much hands-on experience with this event, and Regionals is in a few days >_<. My partner is going to do qualitative analysis, while I do polymers/fibers, some of the crime scene evidence, and the essay. Is it generally a good idea that we start the chromatogram early in the test and write a portion of the essay as soon as we're finished analyzing a piece of evidence?

Edit: (apologize for all of these questions) How can you tell the difference between sodium bicarbonate and carbonate? (as in, what test should you perform?)
Edit 2: Actually, forget about the above edit. Figured it out.

You should definitely start doing chromatography right away so the eluent has time to move the ink molecules up far enough that you can get a good reading on Rf values and such. In terms of the essay, it depends on how fast and how thorough you can be. The way I do essays is, as I mentioned in some post in here before, I write down the names of EVERYONE and next to each person, I write down the things that matched. That gives me a good portion of the points. Then afterwards, if there's time, I write an analysis/conclusion to the essay that states who the suspect is and why. But you should, at the bare minimum, have written everything down that matches each person because the proctor will give you points on the fact that you wrote things down.

OK, thanks. In general, how long should I keep the chromatogram going?

[salcedam]

I haven't had much hands-on experience with this event, and Regionals is in a few days >_<. My partner is going to do qualitative analysis, while I do polymers/fibers, some of the crime scene evidence, and the essay. Is it generally a good idea that we start the chromatogram early in the test and write a portion of the essay as soon as we're finished analyzing a piece of evidence?

Edit: (apologize for all of these questions) How can you tell the difference between sodium bicarbonate and carbonate? (as in, what test should you perform?)
Edit 2: Actually, forget about the above edit. Figured it out.

You should definitely start doing chromatography right away so the eluent has time to move the ink molecules up far enough that you can get a good reading on Rf values and such. In terms of the essay, it depends on how fast and how thorough you can be. The way I do essays is, as I mentioned in some post in here before, I write down the names of EVERYONE and next to each person, I write down the things that matched. That gives me a good portion of the points. Then afterwards, if there's time, I write an analysis/conclusion to the essay that states who the suspect is and why. But you should, at the bare minimum, have written everything down that matches each person because the proctor will give you points on the fact that you wrote things down.

OK, thanks. In general, how long should I keep the chromatogram going?

You should keep the chromatogram going for about 10 - 15 minutes max. You don't want to it run too long or else the water and ink may travel too far up and hit the top of the paper or whatever is suspending the paper over the solution. Use your best judgement as to when to stop. You shouldn't stop it if there's still a lot of ink particles bunched up at the top. Keep it running until you think you've got a nice spread of colors in the ink and you think that there aren't any more particles that need to be separated.

[Dragonshark]

65/100 with 2nd place at regionals. Really need to practice more with this event for state. My partner, despite having 2 years of experience with this event, still got most of the qualitative analysis wrong, probably because we didn't do much practice. I guess I did OK. For hairs and fibers, the proctor gave us some electron micrographs of them. Since some fibers have very distinguishing features (ex. wool), I didn't even need to do any flame tests for them, and just wrote the flame test results from the stuff on my notes. We weren't asked to ID any plastics. The crime scene evidence was only blood typing and fingerprints, which were pretty easy.

The proctor was also nice enough to give us extra time for the essay. I think I got a 24/30 on it even though I had a good logic path, probably because I incorrectly identified some of the evidence, which means the wrong suspects were implicated.

Also, another question: How can you differentiate dog from horse hair? (I got that part wrong on the test.)

[salcedam]

65/100 with 2nd place at regionals. Really need to practice more with this event for state. My partner, despite having 2 years of experience with this event, still got most of the qualitative analysis wrong, probably because we didn't do much practice. I guess I did OK. For hairs and fibers, the proctor gave us some electron micrographs of them. Since some fibers have very distinguishing features (ex. wool), I didn't even need to do any flame tests for them, and just wrote the flame test results from the stuff on my notes. We weren't asked to ID any plastics. The crime scene evidence was only blood typing and fingerprints, which were pretty easy.

The proctor was also nice enough to give us extra time for the essay. I think I got a 24/30 on it even though I had a good logic path, probably because I incorrectly identified some of the evidence, which means the wrong suspects were implicated.

Also, another question: How can you differentiate dog from horse hair? (I got that part wrong on the test.)

Well, good job on your second place! Yeah, Forensics seems like an easy enough event and it really is now that you're allowed to type up your notes and such. When I first started three years ago, I had to make my sheet handwritten and I got such big hand cramps from writing so tiny to fit everything. But despite the easier requirements for notes, it does still take a lot of practice to be able to ID powders and fibers and other things in the qualitative analysis because you need to be able to do them quickly. There are a lot of components as you've seen.

Not quite sure about that one. I just have a picture of both on my sheet and if I get a question like that, I just compare the hairs to the pictures. Sorry. >_<

[cpeters24]

Hey! I have an invitational this Saturday, and my partner and I were double checking the rules. We did not know anything about the cobalt blue glass under flame test equipment that teams are supposed to bring. We have some, but we do not know what it's used for. Can someone help me out with this?

[AlphaTauri]

It's so you can filter out "color contamination" from sodium, which might obscure the true color of the flame. And sodium is everywhere - tap water, sweat from your hands, the team before you who accidentally dropped some powder into the Bunsen burner... Basically, cobalt blue will cancel out the bright orange flame of sodium and let you see if there's another color to the flame.