Forensics C

[wec01]

I was wondering how in-depth I should go when it comes to the powders/crystals. I assume I have to know how they react with different chemicals, the flame tests, what they can be found in, and their chemical formulas. How far should I go after that? Is there anything specific I should know about them?

There are also often questions about different properties of the powders like acidity/basicity, whether it’s a crystal or a powder, etc. That along with what you mentioned should be basically all you need for most questions on most tests. Most of the more uncommon trivia with the powders usually just ends up being different uses for them (e.g. if a suspect is taking medication for bipolar disorder, you should think of LiCl). It sort of falls under what they can be found in, but just be somewhat thorough with it and be sure you can make those connections.

[SilverBreeze]

I was wondering: suggestions for splitting the work during the competition? I'm thinking about a lab/test split carried over from Crime Busters, but I'm worried I'm not doing enough work that way...

[wec01]

I was wondering: suggestions for splitting the work during the competition? I'm thinking about a lab/test split carried over from Crime Busters, but I'm worried I'm not doing enough work that way...

I think having each partner deal with a few types of samples and any related questions (e.g. one does powders, hairs, and fibers and the other does mass spec, fingerprints, chromatography, plastics, and glass) is usually a good way to split the work. Then once one partner finishes they can start working on the conclusion as the other finishes up their part.

[CPScienceDude]

I was wondering: suggestions for splitting the work during the competition? I'm thinking about a lab/test split carried over from Crime Busters, but I'm worried I'm not doing enough work that way...

I think having each partner deal with a few types of samples and any related questions (e.g. one does powders, hairs, and fibers and the other does mass spec, fingerprints, chromatography, plastics, and glass) is usually a good way to split the work. Then once one partner finishes they can start working on the conclusion as the other finishes up their part.

My partner and I are doing a powder/polymer split, and then we just divided the remaining topics evenly amoung us.

[Jonak]

How have people done the flame tests in the past? I've tried dipping the loop in just the powder and in a solution but I can't seem to get any color in the ones that are supposed to have color. I only got a distinct flame with lithium Chloride. Any tips?

[SilverBreeze]

Sometimes your flame is too low temperature, for example with some alcohol lamps. Do you or your school have access to a bunsen burner? Also, making a more concentrated solution and holding it closer to the flame might help. Sometimes you need to wait a while for the flame to show up. Generally, you should at least wait until the metal turns glowing red, at least in my experience.

EDIT: Don't dip it directly in the powder, at least not for the chlorides.

[Jonak]

Sometimes your flame is too low temperature, for example with some alcohol lamps. Do you or your school have access to a bunsen burner? Also, making a more concentrated solution and holding it closer to the flame might help. Sometimes you need to wait a while for the flame to show up. Generally, you should at least wait until the metal turns glowing red, at least in my experience.

EDIT: Don't dip it directly in the powder, at least not for the chlorides.

Yes, I was practicing using a bunsen burner. I didn't really get a clear blue flame, there was some orange in there, would that be an issue? I did heat it until the nichrome wire was glowing red so it should've been good. So I should dissolve a little bit and then dip the nichrome loop in there to do the test?

[Limke]

Sometimes your flame is too low temperature, for example with some alcohol lamps. Do you or your school have access to a bunsen burner? Also, making a more concentrated solution and holding it closer to the flame might help. Sometimes you need to wait a while for the flame to show up. Generally, you should at least wait until the metal turns glowing red, at least in my experience.

EDIT: Don't dip it directly in the powder, at least not for the chlorides.

Yes, I was practicing using a bunsen burner. I didn't really get a clear blue flame, there was some orange in there, would that be an issue? I did heat it until the nichrome wire was glowing red so it should've been good. So I should dissolve a little bit and then dip the nichrome loop in there to do the test?

Typically when I do burn tests, I dip a wooden splint into water and then directly into the powder before I put it in the flame, rather than making a solution. I haven't ever had issues with that. If the flame is mostly blue, it should be fine. Some powders don't really give off a distinct flame.

[SilverBreeze]

Try doing it with the lights off? They tend to show up much better when it's a bit dark. Also, it might be easier to burn off the sodium contaminants from the loop before you dip it in. Does it give off a yellow flame if you just dip it in "pure" water? Sodium is everywhere.

EDIT: Try getting a potassium chloride flame next. That tends to show up best after sodium and lithium.

[Jonak]

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?