Science Crime Busters B

[dholdgreve]

Err, well, I don't know if I got it correct or not, but I do know that my partner and I placed 3rd in the event.... >.<

I don't know about your kit, but the one that my coach gave me was pretty accurate... and when I tested them using the "more unreliable" method, I managed to identify them correctly, with minimal guessing and stuff. Actually, the best way to identify the plastics is still the "better" way with vegetable oil, etc. for me, although the supervisor may not provide that stuff.

As to the accuracy of the Wiki, I'm not entirely sure, since I have only editted a little bit of it. I don't know who added the information about the plastics. I also don't know if anyone has really actually verified any of the information to be true... (I guess I've always taken the Wiki information as for granted and always true.... Good point. >.<)

As for PETE and PVC, according to the Wiki, PVC is also slightly rubbery.... so maybe, texture (if you are allowed to touch the actual tangible substances)?

I'd trust the wiki before I'd trust the paper that comes with the polymer samples... It's just flat wrong.

[rockernerdzgurl]

Well, I don't know about you, but I find mixtures pretty hard. They're the ones that trick me up the most, so that's something that I let my partner do. However, fibers is also something that I'd rather give over to someone else. What I find the easiest is plastics, metals, and liquids, as well as the conclusion/short answer analysis questions. Honestly, the metals and liquids are pretty basic, and almost anyone could figure them out, but I tend to be quicker than my partner at identifying those. The powders are somewhat medium-ish to me, because some (like alka seltzer) are really noticeable and easy to identify with one drop of HCl, but others, (can't think of one off the top of my head) are a little harder. Mostly, it just depends on what you are the best at. Some things that your partner find easy might be a little more challenging to you. (But I guess the chromatography part is always really easy, huh?) So play off each others' strengths and weaknesses!

Yeah mixtures are the worst. Especially when you don't know if it even is a mixture!

[T-B]

Help on fibers. At our regionals, they didn't let us use a microscope or burn, so we were hopeless at IDing them. Is there some other way to ID fibers that we didn't know? The just wanted to know animal, veg or synthetic, but still... We were clueless. Help!

[Mandy and Aubby]

Try this cite: http://www.fabrics.net/fabricsr.asp. I think it might contain something about how to identify fibers without burning. good luck! sorry if it doesn't help.

[willowmist]

I don't think there is any way besides burning and microscope identification, but you could try looking at the fiber without a microscope. In general, natural (animal and vegetable) fibers are shorter and more twisted together, with loose ends sticking out like fuzz. Synthetic fibers are smoother, have uniform thickness, and resemble silk. I don't know how much that will help, but... I'm guessing at States they'll probably give you materials for at least one of the two methods? At my State competition, they gave us pictures of the fibers, and although they were not very magnified, they were enough for us to identify the fibers.

[icyfire]

Does making a wet mount slide when preparing a hair for the microscope help a lot more for the amount of time it takes, rather than just putting a hair/fiber on a dry slide? Because making wet mounts for several fibers could take precious time that could be spent doing other things.

[poparteeb2]

A strategy I use for seeing if baking soda is with alka seltzer is separating them a bit, then drop water into what I think is the alka seltzer, and then dropping water into what I think is the baking soda.

Anyways, for some reason I'm having a lot of trouble with the metals. First--I simply cannot tell the difference between aluminum and tin. Because the samples are so small, I can't tell which one's heavier. No one reacts. I can't tell if it's "yellowish" or not without another frame of reference. How do you guys figure it out?

Also, will they give you different "forms" of the metals? So far I've gotten aluminum foil, aluminum lumps (like little balls of aluminum), tin foil, dull lumps of zinc, zinc filings, iron filings, magnesium pellets, copper strips, and copper lumps. Are there any other "forms" (like balls, strips, etc.) of the metals, because the different forms really look different....?

[Silkfern]

A strategy I use for seeing if baking soda is with alka seltzer is separating them a bit, then drop water into what I think is the alka seltzer, and then dropping water into what I think is the baking soda.

Anyways, for some reason I'm having a lot of trouble with the metals. First--I simply cannot tell the difference between aluminum and tin. Because the samples are so small, I can't tell which one's heavier. No one reacts. I can't tell if it's "yellowish" or not without another frame of reference. How do you guys figure it out?

Also, will they give you different "forms" of the metals? So far I've gotten aluminum foil, aluminum lumps (like little balls of aluminum), tin foil, dull lumps of zinc, zinc filings, iron filings, magnesium pellets, copper strips, and copper lumps. Are there any other "forms" (like balls, strips, etc.) of the metals, because the different forms really look different....?

Same here. The dull lumps of zinc you got are probably mossy zinc (molten zinc dropped into water), which looks absolutely nothing like normal zinc.
Obviously, iron is magnetic (it also rusts after contact with water), and copper is copper. Tin foil actually does have a yellowish sheen, but it can be quite variable. The tin foil that I got was dull but rather reflective, and the "yellowness" of it was fairly obvious when compared with other metals. Just compare it with your tweezers/metal scoops/test tube rack/etc., and if you don't have any of those, just bring a paper clip or something. Aluminum tends to be brighter and more silvery, and when I tested it, it also didn't react with HCl.

[geekychic11]

that wont always work

[geekychic11]

that wont always work