Science Crime Busters B

[geminicross]

http://en.wikipedia.org/wiki/Bloodstain_pattern_analysis

Before asking for help, I would highly suggest running a simple google/bing/whatever-search-engine-floats-your-boat search on any topic you want to know about for SCB. Most of my notes for Forensics come from a simple google/wikipedia search (and the 2-inch thick pile of notes I inherited from former competitors, which is mostly wikipedia anyways).

Thanks, we were able to cover it, during practice.
We just used coffee instead of Blood

[Mackorny]

Information is good and very informative!


earthwork

[EpicFailure]

We have had a lot of trouble identifying mixtures. Can someone give us some tips? Thanks!

[Skink]

Information is good and very informative!
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I've had trouble with this, too, so I don't have perfect advice. All you can really do is make a bunch of combinations--as many as you have time and supplies for--and then see if you can ID them later. Practice. When given an unknown, you have to be methodical. Are there two powders? Two granular ones? A mix? If you can identify what consistency your mixture has right off the bat, you're in better shape. Look at the components, identify what you think they might be, and run a few tests to see if you might be right. If you can knock one of them off, you can sometimes treat the second one as a single mixture and just run through the flow chart, keeping in mind that you know the first one and MAY see reactions from it and not the unknown you're trying to ID. Make sense?

There's no easy way to do this, unfortunately.

[EpicFailure]

Information is good and very informative!
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I've had trouble with this, too, so I don't have perfect advice. All you can really do is make a bunch of combinations--as many as you have time and supplies for--and then see if you can ID them later. Practice. When given an unknown, you have to be methodical. Are there two powders? Two granular ones? A mix? If you can identify what consistency your mixture has right off the bat, you're in better shape. Look at the components, identify what you think they might be, and run a few tests to see if you might be right. If you can knock one of them off, you can sometimes treat the second one as a single mixture and just run through the flow chart, keeping in mind that you know the first one and MAY see reactions from it and not the unknown you're trying to ID. Make sense?

There's no easy way to do this, unfortunately.

We've tried mixing different powders together and recording the results but I don't feel like it's very helpful. In the past, we've always had trouble with (powder) powder mixtures. For example, we once had cornstarch/flour & baking soda and cornstarch/flour & gypsum (?). The 2nd mixture was a brighter white than the 1st mixture, which would indicate it's cornstarch & gypsum. However, the first mixture didn't clump in water as flour would have, so it seemed like it was cornstarch. We've compared the colors of baking soda and gypsum before and they're both pretty much the same shade of white. pH didn't help much. I've heard of a way to separate the powders by pouring them out and shaking to separate them, but the powders were so well mixed it looked like a single powder.

[geekychic13]

SOooooooooo...anyone here doing this event in illinois regionals??? cuz i am and im wondering if there will be burn tests this year...okay so you guys probably wont know that...but just wondering...and you can't burn plastics, you only get results, right? cuz last year we didnt have naything with burn tests but at state we did so...

[EpicFailure]

The only things you can burn are fibers (and usually with candles). The burn tests are not usually very hard, you just have to know that animal fibers smell like burning hair, burnt plant fibers look like burnt edges of paper and it smells like burning paper too, and synthetic fibers melt/curl after they're burnt and sometimes smell like burning plastic. If they're asking for natural vs. synthetic, you just have to remember that synthetic fibers melt/curl when they're burnt.
I think the reason that they don't allow you to burn plastic is because the odor might be harmful (?) and it's sort of dangerous.

[AlphaTauri]

Correct, most synthetic fibers "shrink" and curl away from the flame (excepting spandex, which I don't know is part of SCB anyways). If they ask you to identify individual kinds of fibers - like wool, cotton, nylon, linen, etc - it's easy to search something to the effect of "fibers burn test results" and pull together some info from the web.

And yeah, they don't allow you to burn plastics because some of them release all kinds of nasty carcinogens into the air...plus it's a bit of a mess to clean melted and re-solidified plastic off the lab tables.

[BruteForceRacer]

Do you think I need to practice using powders,liquids,metals, etc? My coach hasn't brought in the materials yet and the invatational I'm going to is in two weeks

[EpicFailure]

Do you think I need to practice using powders,liquids,metals, etc? My coach hasn't brought in the materials yet and the invatational I'm going to is in two weeks

It's always helpful to go over (/put on the cheat sheet) the flowcharts/properties of powders/liquids/metals (found on the wiki) and research the common uses of these unknowns when you have time. Two weeks is always a lot shorter than it seems.

[SciBomb97]

You know, having a lot of knowledge usually doesn't cut it in events like these. Until you actually try doing some of the tests, it's hard to get used to doing everything in the way you're supposed to. For instance, testing solubility is simply in theory, but having experience with how much of the substance and water to use is important.

[geminicross]

You know, having a lot of knowledge usually doesn't cut it in events like these. Until you actually try doing some of the tests, it's hard to get used to doing everything in the way you're supposed to. For instance, testing solubility is simply in theory, but having experience with how much of the substance and water to use is important.

Yeah, though last year I was relying on my ability to see words in tiny font and 7th grade education to win. (3rd place wasn't too bad, considering I had no partner) The more things you already know, the more space for other things on your cheat sheet.

At least this year I was able to be prepared, Regionals should go over well.

[EpicFailure]

It's good to have experience with the actual materials, but much of the test is written work & concepts - at least from the competitions I've been too. It's generally helpful to have an idea what the powders look like & their reactions, what the liquids smell like and view fibers/hairs under a microscope, but you wouldn't need that much lab experience. (Esp. fibers/hairs as most proctors like to get the pictures from the internet.) Also, a cheat sheet is VERY important. Being familiar with the lab part and having a poor, incomplete cheat sheet doesn't really get you anywhere.

[outofsight13]

At the competition, will we be given distilled water or tap water for testing?

[EpicFailure]

At the competition, will we be given distilled water or tap water for testing?

Probably distilled water, as it says in the rules. We've tried with tap water before and the reactions weren't as clear.