Forensics C

[pikachu4919]

For the Rfs of different molecules on nationals tests, the answer key usually just says things like 0.97, 0.55, 0.34, 0.24. Do they allow for a range of answers, so if I say 0.95, 0.59, 0.32, 0.22, will they accept that as valid, or will they only accept exactly what they have, can somebody with experience answer this?

Also, how does fluorescence work? Do we just take the gel-paper thing and shine a "flashlight"/blacklight at it? Are there two buttons on the blacklight for long and short wave length?

You definitely don't want to be off by too much but I would think so (then again they never return your nats tests so in reality you will never know).

And for your second question:

Regarding national tests, what is fluorescence? What area (chromat, fibers, blood, or chem) of the event is it about? And what do we have to know about it, and what are websites that can give enough info?

The fluorescence is part of the TLC (thin layer chromat) you'll be doing on samples of different kinds of paints. iirc you perform the TLC on the paint and see if your sample will glow under different wavelength settings of a blacklight, and that's most of what you do.

[Abekitt]

At regional, there were questions about the "medulla index" for each type of hair. As far as I can tell, they probably meant the medullary index, and this is not dependent on the type of hair. Does anyone know what the medullary index would be for each hair?
Also, does anyone know the index of refraction for types of glass? I know that for glass analysis, the glass dissapears in the liquid with the same index of refraction, but without knowing what kind of glass has that index of refraction, I'm not sure what I would do with that information, and I was asked to identify the type of glass at regional.

You can look up average/common medullary indexes. This was the first thing I got when I googled, but you should cross-check with other sources. http://www.aquinashs.org/ourpages/auto/ ... on%201.ppt

For glass, I usually keep a chart of indexes for common things that show up. Again, google for them. Definitely know crown glass.

What kinds of glass do we need to know, is the list on the rule chart? Did you use a specific website for it, or did you just search the glass with the word refac index?

[sciduck]

At regional, there were questions about the "medulla index" for each type of hair. As far as I can tell, they probably meant the medullary index, and this is not dependent on the type of hair. Does anyone know what the medullary index would be for each hair?
Also, does anyone know the index of refraction for types of glass? I know that for glass analysis, the glass dissapears in the liquid with the same index of refraction, but without knowing what kind of glass has that index of refraction, I'm not sure what I would do with that information, and I was asked to identify the type of glass at regional.

You can look up average/common medullary indexes. This was the first thing I got when I googled, but you should cross-check with other sources. http://www.aquinashs.org/ourpages/auto/ ... on%201.ppt

For glass, I usually keep a chart of indexes for common things that show up. Again, google for them. Definitely know crown glass.

What kinds of glass do we need to know, is the list on the rule chart? Did you use a specific website for it, or did you just search the glass with the word refac index?

I did the latter. I don't believe there is a list, I just looked at old tests to pick the important ones.

[19sawickin]

Did anyone take the Pennsylvania State Tournament Forensics test? It is always written by Harriton and is, in my opinion, by far the hardest test I have ever taken, national tests included. This year I believe there were 10 powders to test and 11 polymers, 5 of which were plastics that were easy enough to ID, the difficulty lying in the 6 different fabrics/hairs. Now, traditionally, I identify fabrics by burning them and observing their odors and how they react in the flames. I can also identify certain fabrics under a microscope, as long as they are natural fibers (is there anyway to distinguish synthetic ones from each other??). However, they only gave one tiny thread for each of the two fabrics, and single hairs that were even a challenge to find inside of the little bag that they were in. Furthermore, there were only two low-quality microscopes inside of the room for the 10 or so teams to share.

My question is, how can one possibly ID those hairs/fabrics if they didn't use a microscope? Is that even possible? Is it even the right strategy to try and identify the hairs under the microscope since it takes an exorbitant amount of time to place the hairs on the microscope slips and even locate them under the microscope? There was significantly more to the test than just ID-ing, so should I just skip the hairs???? I'm utterly confused, especially since I was using a microscope for an extended period of time, long enough to (unintentionally) prevent a team who placed from using the microscope (I'm fairly confident).

Anyone who took this PA test PLEASE help me understand how this test was "extremely easy."

[Magikarpmaster629]

So on the nationals website there are images of the rooms for every events except Forensics (here). Anyone involved in nats know if this is on purpose, or if someone just overlooked it?

[daydreamer0023]

Anyone have a good way to distinguish nylon vs polyester?

[markuswso17]

Anyone have a good way to distinguish nylon vs polyester?

Under a microscope, Nylon looks like small clear rods. Polyester is the same thing but it isn't clear.
During burn test, Nylon curls when a few inches away form the flame while Polyester does not.

[pikachu4919]

Anyone have a good way to distinguish nylon vs polyester?

Under a microscope, Nylon looks like small clear rods. Polyester is the same thing but it isn't clear.
During burn test, Nylon curls when a few inches away form the flame while Polyester does not.

You might also want to read up on the chemical makeups of each fiber, they can also tell you about chemical properties that the fibers might have (such as scent in the burn test, behavior during the burn test, etc.)

I think I know who both of you are and that you'll both be in this event at nationals, so here's a tip from me: The microscopes at nats aren't top-notch quality (believe me, I know) - sometimes, they might not really give you a good view of whatever you're looking at, and/or it is hard to quickly adjust the microscope to a good, focused view. That plus the fact that time flies so quickly at nats due to the sheer amount of stuff that the supervisor makes you do means that you possibly won't have that much time to do a microscope analysis if you're really really pressed - for me when I took this supervisor's exams, that's why I actually relied more on burn tests and my gut feelings/instinct for fiber and hair ID.

[KSSOISLIT]

For the Nationals test, does the Woz set up slides with hair on microscopes, or do we have to prepare slides with hair they give us?

[KSSOISLIT]

Another question, what would be the best way to distinguish between PP and LDPE as they behave similarly in most density tests and have similar appearances?