Forensics C

[kek16]

I'm not going to nats but I was just curious, how do you guys practice for forensics over the summer?

[wec01]

I'm not going to nats but I was just curious, how do you guys practice for forensics over the summer?

If you are willing to spend the money you can buy a lot of the materials online through Science Olympiad or other companies. You can surprisingly even get cheap equipment and make it work (I have a cheap, plastic, battery-powered microscope which works alright for practicing). Still, some of the setup is unreasonable, especially the bunsen burners, but I've heard of people being a little sketchy and using a stovetop (probably not recommended though).

I'm not sure if this is a viable option, but maybe some schools or labs would let you go over the summer to practice? Still, it seems like it would be a hassle to arrange, if at all possible.

[c21k]

I'm not going to nats but I was just curious, how do you guys practice for forensics over the summer?

If you are willing to spend the money you can buy a lot of the materials online through Science Olympiad or other companies. You can surprisingly even get cheap equipment and make it work (I have a cheap, plastic, battery-powered microscope which works alright for practicing). Still, some of the setup is unreasonable, especially the bunsen burners, but I've heard of people being a little sketchy and using a stovetop (probably not recommended though).

I'm not sure if this is a viable option, but maybe some schools or labs would let you go over the summer to practice? Still, it seems like it would be a hassle to arrange, if at all possible.

Yeah, the stove top seems really sketchy...also using a bunch of chemicals in your kitchen...depending on your parents this may be seen as unacceptable. I won't be competing anymore in the future--Div D now :'( --but i'll be in the lab before the school year ends to take videos of each chemical burning and reacting with HCl, Benedicts, Iodine, and testing pH for future competitors look at in order to prep during the summer. I know it's not ideal, but at least they will be familiar with what everything at least LOOKS like and how to conceptually run the tests.

For fibers, I'll probably do something similar, but time is a factor so i'll have to see if I even get around to doing it. As for the microscopic images, we usually just look up a BUNCH of images online and get very familiar with them. Plastics, to be honest, I've never felt the need to practice, but that's just me. If you really wanted to, you could obtain all the different density solutions and plastics to test.

(I've also made an evil move and took away the cheatsheet from this year --- i made it -- and told my forensics partner to make his own for the next season because it'll help him learn. I don't know if this was a smart move at all on my part but I guess we'll see ¯\_(ツ)_/¯ )

[fastllama]

I did the NSO forensics test from last year and was wondering if anybody who's had experience doing forensics at nationals would be willing to help out an inexperienced competitor :')

This is a weird question, but I wanted to ask because I usually id sucrose immediately based on its crystals. Have they ever given you sucrose (or what you thought to be sucrose since you wouldn't have gotten your tests back) in powdered sugar form?

In one of my tests, I've noticed that Ammonium Chloride produces lots of smoky wisps in the bunsen burner flame test and Calcium Nitrate completely turns into water?? I tested it repeatedly and found consistent results. However, I thought that was strange since I've never seen that written in any notes online. We only recently got a bunsen burner to practice, so we had only been using an alcohol burner and didn't observe these effects. Has anyone else had experiences with the powders reacting this way?

For fiber burn tests, do we use a bunsen burner or a separate flame?

How do you perform paint chromatography and identify the fluorescence and wavelength? Like what is the actual procedure?

The fingerprint labeling/identification section was very very hard to see in last year's test. Maybe it was just the printing, but how did you guys do it? The mass specs were also hard to read, but it was just extremely small. Are the pictures of these on the actual test usually clearer somehow? I just don't understand how anyone could be able to see them based on the pictures on the test.

--Thank you so much!

[wec01]

I did the NSO forensics test from last year and was wondering if anybody who's had experience doing forensics at nationals would be willing to help out an inexperienced competitor :')

This is a weird question, but I wanted to ask because I usually id sucrose immediately based on its crystals. Have they ever given you sucrose (or what you thought to be sucrose since you wouldn't have gotten your tests back) in powdered sugar form?

In one of my tests, I've noticed that Ammonium Chloride produces lots of smoky wisps in the bunsen burner flame test and Calcium Nitrate completely turns into water?? I tested it repeatedly and found consistent results. However, I thought that was strange since I've never seen that written in any notes online. We only recently got a bunsen burner to practice, so we had only been using an alcohol burner and didn't observe these effects. Has anyone else had experiences with the powders reacting this way?

For fiber burn tests, do we use a bunsen burner or a separate flame?

How do you perform paint chromatography and identify the fluorescence and wavelength? Like what is the actual procedure?

The fingerprint labeling/identification section was very very hard to see in last year's test. Maybe it was just the printing, but how did you guys do it? The mass specs were also hard to read, but it was just extremely small. Are the pictures of these on the actual test usually clearer somehow? I just don't understand how anyone could be able to see them based on the pictures on the test.

--Thank you so much!

I don't recall ever getting sucrose in powdered from, but if you do, it theoretically would just appear to be glucose in terms of the burn test, pH, solubility, etc. and only differ with Benedict's. So basically, I would say if it looks like sucrose, it probably is, but if you think something is glucose, use Benedict's to make sure (although theoretically glucose can be found in crystals as well, so maybe use Benedict's for both to be safe).

I've also noticed that calcium nitrate melts and ammonium chloride produces smoke (also the smoke sometimes smells somewhat acrid), but if you're nervous about the reliability of that there are other more definitive tests for those powders, especially ammonium chloride. I'm not sure why it wouldn't happen with an alcohol burner, but it might have something to do with the size or temperature of the flame.

For fibers, you're provided a candle at competition which you can use. The bunsen burner will work, but the flame is so large it's easy to miss things.

For the paint chromatography, I believe the setup is pretty much the same as paper chromatography just with different materials, all of which will be provided at competition. For the fluorescence, there is a blacklight at competition with different settings so you would just place the finished chromatography under the blacklight at each setting and see whether anything fluoresces.

Unfortunately, the images at competition were pretty much how they appeared in the digital version. For me at least, the fingerprint section was pretty much just circling vague features and hoping for the best. Some of the past nationals tests were somewhat clearer, but in general, just do your best, as far as I know, there's not much you can do about it. For mass spec, as you said, it's mainly just printed very small. Luckily, the test usually just asks you to match the crime scene samples with a suspect and list some values like molecular weight, so it's more reasonable, you just have to be careful and look very closely.

[pikachu4919]

I did the NSO forensics test from last year and was wondering if anybody who's had experience doing forensics at nationals would be willing to help out an inexperienced competitor :')

The last time I did a test by that exact same supervisor was in 2016, so it's been a while, but the supervisor is from my state, and from word of mouth from more recent competitors, I've heard not much has changed (although there might be some that has), so I guess I can offer some advice.

This is a weird question, but I wanted to ask because I usually id sucrose immediately based on its crystals. Have they ever given you sucrose (or what you thought to be sucrose since you wouldn't have gotten your tests back) in powdered sugar form?

I don't recall ever getting sucrose in powdered from, but if you do, it theoretically would just appear to be glucose in terms of the burn test, pH, solubility, etc. and only differ with Benedict's. So basically, I would say if it looks like sucrose, it probably is, but if you think something is glucose, use Benedict's to make sure (although theoretically glucose can be found in crystals as well, so maybe use Benedict's for both to be safe).

Glucose generally does have a more "powdery" appearance than sucrose, which tends to have a much larger crystal structure (or perhaps a near cuboidal crystal structure like salt, although that's more rare). But yes, you should definitely use Benedict's to confirm it. By the way, you can tell if it's either one of those sugars by burning it dry on a spatula - it'll caramelize, just like when you cook down sugar to make homemade caramel. (By the way - three syllables. Not two. Guess why I say that?)

In one of my tests, I've noticed that Ammonium Chloride produces lots of smoky wisps in the bunsen burner flame test and Calcium Nitrate completely turns into water?? I tested it repeatedly and found consistent results. However, I thought that was strange since I've never seen that written in any notes online. We only recently got a bunsen burner to practice, so we had only been using an alcohol burner and didn't observe these effects. Has anyone else had experiences with the powders reacting this way?

I've also noticed that calcium nitrate melts and ammonium chloride produces smoke (also the smoke sometimes smells somewhat acrid), but if you're nervous about the reliability of that there are other more definitive tests for those powders, especially ammonium chloride. I'm not sure why it wouldn't happen with an alcohol burner, but it might have something to do with the size or temperature of the flame.

All of those are correct. It is true that alcohol burners generally are not as hot as Bunsen burners, and are thus not always able to provide enough energy to excite the electrons enough to a state that then affects light emission as they drop back to their ground state. Quantum chemistry, yo! It's important but apparently far too complex for the nats supervisor. But calcium nitrate should also give off the reddish orange flame, it's very distinct from the golden flames of sodium, if you do a comparison. But yes, there are easy confirmative tests you can perform for both.

For calcium nitrate, dissolve it in water and add NaOH. If it is calcium nitrate, you'll see a milky white substance form, which is a precipitate (calcium hydroxide). The other two calcium compounds may also form calcium hydroxide precipitates, but they also aren't as soluble in water as calcium nitrate, which is the key to differentiation.

For ammonium chloride, you just need to add Benedict's solution to the dry powder, and it'll form a complex ion with the copper that causes it to turn a really dark blue (like noticeably compared to the hue of blue that Benedict's is). That's its confirmatory test.

For fiber burn tests, do we use a bunsen burner or a separate flame?

For fibers, you're provided a candle at competition which you can use. The bunsen burner will work, but the flame is so large it's easy to miss things.

You'll get a candle. However, there's a chance it might not work, because the supervisor rarely changes out her supplies. You might get a candle with barely any wick or barely any wax or something, which is a huge rip but uncontrollable by the rest of the world. But I would highly recommend avoiding using the Bunsen burner if possible. It's often too hot and too big for fibers, especially the small threads that you'll get, and it'll basically incinerate whatever you have to the point where it leaves nearly nothing behind. Maybe sneak in a small generic tea light if you can just in case the supervisor's candle that she gives ya doesn't work and hope you don't get caught (at the very least, she'll probably just confiscate it if she catches it and decides to not let you have it).

How do you perform paint chromatography and identify the fluorescence and wavelength? Like what is the actual procedure?

For the paint chromatography, I believe the setup is pretty much the same as paper chromatography just with different materials, all of which will be provided at competition. For the fluorescence, there is a blacklight at competition with different settings so you would just place the finished chromatography under the blacklight at each setting and see whether anything fluoresces.

Correct. Paint chromatography is performed on TLC (thin layer chromatography). It's basically a small plastic plate with a silica coating. The procedure is the same as paper chromatography, just with different media. wec01 is right about the blacklight, although I honestly skipped that part since I felt I could maximize points across other areas of the test (aka the trivia, although I'm not sure how much trivia there is nowadays).

The fingerprint labeling/identification section was very very hard to see in last year's test. Maybe it was just the printing, but how did you guys do it? The mass specs were also hard to read, but it was just extremely small. Are the pictures of these on the actual test usually clearer somehow? I just don't understand how anyone could be able to see them based on the pictures on the test.

Unfortunately, the images at competition were pretty much how they appeared in the digital version. For me at least, the fingerprint section was pretty much just circling vague features and hoping for the best. Some of the past nationals tests were somewhat clearer, but in general, just do your best, as far as I know, there's not much you can do about it. For mass spec, as you said, it's mainly just printed very small. Luckily, the test usually just asks you to match the crime scene samples with a suspect and list some values like molecular weight, so it's more reasonable, you just have to be careful and look very closely.

Yep to all of that. Neither rarely ever prints out that clearly honestly, so do your best.

--Thank you so much!

[fastllama]

Wow guys, thanks for the detailed answers and explanations!
How much time would you guys generally allot for the analysis?

[wec01]

Wow guys, thanks for the detailed answers and explanations!
How much time would you guys generally allot for the analysis?

I think it varies from team to team, but personally, my partner and I usually just have whoever finishes their identification first start on the conclusion. If the test is taking awhile, we try to give ourselves maybe 5-10 minutes at the end. With the nationals test, I'd say the conclusion goes a little faster than normal (at least compared to my experiences at states) just because the scenario/evidence tends to be somewhat simpler than normal.

[fairfaxfan123]

Hey for the Paper chromatography last year at nationals I remember they wanted us to use sheet chromatography and in a petri dish. Does anyone know how to do this or if I'm remembering wrong if they could tell me what they had us actually do for the chromatographies?

[wec01]

Hey for the Paper chromatography last year at nationals I remember they wanted us to use sheet chromatography and in a petri dish. Does anyone know how to do this or if I'm remembering wrong if they could tell me what they had us actually do for the chromatographies?

https://www.soinc.org/sites/default/fil ... graphy.pdf