Science Crime Busters B

[Skink]

Majority? Keep in mind, as far as scoring is concerned, unknown ID--mostly powders--is 50%. That's a 50% you can't afford to lose, but don't skip practicing everything else, either.

[geminicross]

There are a lot of things to learn. Based of past experience a majority of the test is ID of the powders and mixtures. So my suggestion is to talk to your coach about getting the needed powders and then start practicing how you can ID them. Maybe make a dichotomous key

I strongly agree. The majority of the test will in fact be powders, but you might also want to take a look at liquids and metals too, since the liquids are commonly found lying around the house, and you might have better access to them. Once you feel like you got the hang of recognizing individual powders, then you should start moving onto mixtures of 2, then 3 if you feel braver. However, the event isn't just identification. You'll have to know things like types of fingerprints (which is pretty basic), as well as what certain types of fibers and hairs look like under microscopes. Those are the most common things seen in the competition setting, and should be enough to get you started. Also, you might want to take a lot of practice tests with your partner - find out who is better at doing what. For example, my partner and I have worked out a system that allows us to use our 50 minutes of event time the most efficiently. You can either split up the work or work together, although I do recommend from previous experience to split up the work because the time you have is limited.

Do you have any info on analyzing blood spatters?

[AlphaTauri]

http://en.wikipedia.org/wiki/Bloodstain ... n_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).

[outofsight13]

Will we have to construct and bring a paper chromatogram, for testing, to the competition? Or do we just have to know what they are and how they work?

[Skink]

You will have to go to competition and make a chromatogram. The supervisor will provide the materials, but know how to do it. It's easy points lost, otherwise.

[geminicross]

http://en.wikipedia.org/wiki/Bloodstain ... n_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!
.
..
...

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.