Forensics C

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Re: Forensics C

Post by SilverBreeze » December 23rd, 2019, 7:04 pm

Jonak wrote: I did the flame test with the lights off. I previously read that sodium contamination was a thing so I was looking out for that, but I never got a yellow flame, even with sodium bicarbonate and sodium carbonate. With just water the flame was orange which I was previously told it was from the nichrome wire? I've also tried potassium chloride with no success. Can we use wooden splints to do the flame test? The rules say "Flame loop" but how specific is that?
Orange... Is your water hard? That reminds me of the calcium flame a bit. Check with your tournament director or proctor about wooden splints, but there's no logical reason to prohibit them. Try to stick with a flame loop, just to avoid headaches. Try switching flame loops? Maybe it's the loop itself? Is the orange color obscuring the compound colors?

I don't really know at this point, but maybe the temperature is too high or too low? Try adjusting them using the air holes at the bottom of the burner, if you're using the same kind I am. There are some videos online for flame tests, so maybe watch them and see where your lab technique is different, and try adjusting that?
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Re: Forensics C

Post by Jonak » December 25th, 2019, 3:07 pm

SilverBreeze wrote:
Jonak wrote: I did the flame test with the lights off. I previously read that sodium contamination was a thing so I was looking out for that, but I never got a yellow flame, even with sodium bicarbonate and sodium carbonate. With just water the flame was orange which I was previously told it was from the nichrome wire? I've also tried potassium chloride with no success. Can we use wooden splints to do the flame test? The rules say "Flame loop" but how specific is that?
Orange... Is your water hard? That reminds me of the calcium flame a bit. Check with your tournament director or proctor about wooden splints, but there's no logical reason to prohibit them. Try to stick with a flame loop, just to avoid headaches. Try switching flame loops? Maybe it's the loop itself? Is the orange color obscuring the compound colors?

I don't really know at this point, but maybe the temperature is too high or too low? Try adjusting them using the air holes at the bottom of the burner, if you're using the same kind I am. There are some videos online for flame tests, so maybe watch them and see where your lab technique is different, and try adjusting that?
I was using distilled water so that shouldn’t have been the case? I was using distilled water to wash too. I’m thinking you’re right and it was either too hot or not hot enough, I didn't play too much with the air holes though so maybe I can try that next.

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Re: Forensics C

Post by TheRarePinkSheep » January 1st, 2020, 9:00 am

Hello! I was scrolling through the forums and someone said not to dip directly into the chlorides, why exactly? I've had no problems directly dipping into the powders with a wet flame loop. Does it affect the results?

Also I've found difficulty with getting the potassium flame. I don't know whether it is because of sodium contamination or a poor flame, though a result does show up. Rather than the classic lilac flame, it is more of a peachy yellow that's not the glaring yellow of potassium.
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Re: Forensics C

Post by SilverBreeze » January 1st, 2020, 1:00 pm

TheRarePinkSheep wrote:
January 1st, 2020, 9:00 am
Hello! I was scrolling through the forums and someone said not to dip directly into the chlorides, why exactly? I've had no problems directly dipping into the powders with a wet flame loop. Does it affect the results?

Also I've found difficulty with getting the potassium flame. I don't know whether it is because of sodium contamination or a poor flame, though a result does show up. Rather than the classic lilac flame, it is more of a peachy yellow that's not the glaring yellow of potassium.
Ah, that would be me. For me, the solution tends to be too concentrated and dry onto the flame loop. It's hard for me to get off and contaminates future results, especially since I practice with an alcohol lamp, which has a lower temperature than a bunsen burner. That means I can't check whether all of the powder came off until it's too late(as I found out the hard way). The test itself turns out fine, and if it works for you, keep doing it.

There might be slight sodium contamination, but not enough to block out the potassium. Also, for me, the flame doesn't turn up a vivid lilac, but more a faint lilac with a lot of yellow and orange mixed in. There are videos of flame tests on YouTube, I believe, and watching those might help you determine if that's just the way you perceive the flame. It might also be your lighting, and you can try turning off the lights when practicing.
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Re: Forensics C

Post by WangwithaTang » January 28th, 2020, 4:32 pm

How would you guys recommend studying for plastics?

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Re: Forensics C

Post by Limke » February 4th, 2020, 6:05 am

WangwithaTang wrote:
January 28th, 2020, 4:32 pm
How would you guys recommend studying for plastics?
I would recommend repetitive practice with density solutions. Test each plastic (knowing what it is) in each solution to see what happens and take notes. After you've gotten a "feel" for the behavior of each plastic in different solutions (floating or sinking), I would just keep doing random practice tests with unknown samples and then check your answers. Whenever you get one wrong, just retest it.

Also, if possible (with the supervision of a teacher/coach, a fume hood, and other appropriate safety equipment), it may be helpful to burn the plastics (knowing what they are) so you can take notes on their behavior and observe what they do. Not all event supervisors will burn plastics, but I know my state event supervisor typically does.

With all physical evidence (fibers/powders/plastics), you are limited to what samples you can be tested on. Constant repetition and being familiar with the behavior of your samples is the best way to correctly ID them each time.
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Re: Forensics C

Post by RavidD » February 10th, 2020, 11:03 am

Any recommendations for metal shavings? For some reason it's one of the only ones giving me trouble.

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Re: Forensics C

Post by CPScienceDude » February 10th, 2020, 11:47 am

RavidD wrote:
February 10th, 2020, 11:03 am
Any recommendations for metal shavings? For some reason it's one of the only ones giving me trouble.
There are no metal shavings in Forensics. If you're in Crime Busters, though, here is a good resource: http://mypage.iu.edu/~lwoz/socrime/metanal.htm
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Re: Forensics C

Post by jaspattack » February 11th, 2020, 1:21 pm

Since the rules say one note sheet per participant you can have two sheets front and back total for this event, correct? I'm working on mine for regionals and while my key for powders isn't done yet, I don't see myself needing to use the whole four pages...
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Re: Forensics C

Post by CPScienceDude » February 11th, 2020, 4:29 pm

jaspattack wrote:
February 11th, 2020, 1:21 pm
Since the rules say one note sheet per participant you can have two sheets front and back total for this event, correct? I'm working on mine for regionals and while my key for powders isn't done yet, I don't see myself needing to use the whole four pages...
If you’re soloing, then you only get one page. If you have a partner, then yes, you get 2 front and back pages.
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