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Re: Crime Busters B
Posted: February 17th, 2019, 10:45 pm
by jimmy-bond
CPScienceDude wrote:I'm curious as to how you guys differentiate between PETE and PVC. When it gets down to those 2 it gets kinda dicey. I know PETE is always clear, and on the CB sheet that the people before me made it said that PVC is never clear. I looked it up, though, and I found a lot of conflicting information about if PVC can be clear or not. For the sake of this, assume that you are given a hard, clear plastic that sinks in all the solutions. You get it between PVC and PETE. Where do you go from there?\
EDIT: No burn test results or common uses were given either.
PVC is indeed never clear. Apparently maple syrup has a density of 1.37, so that would narrow it down. If it's clear, however, I would say PETE.
Re: Crime Busters B
Posted: February 18th, 2019, 9:39 am
by utumn
I'm doing some quick notes before regionals and I have a very important question about fibers!
All the information that I've found thus far has shown me how to ID fibers with burn tests, but I've been told by some people that there won't be burn tests happening at the event. Is that true? If so, how do I ID fibers without burning them?
Re: Crime Busters B
Posted: February 18th, 2019, 9:49 am
by amk578
utumn wrote:I'm doing some quick notes before regionals and I have a very important question about fibers!
All the information that I've found thus far has shown me how to ID fibers with burn tests, but I've been told by some people that there won't be burn tests happening at the event. Is that true? If so, how do I ID fibers without burning them?
Whether or not burn tests are happening is up to the specific tournament, i.e. you can't always rely on just burn tests happening. If you won't be conducting burn tests, there are either two things happening. One, the test will give you a description of WHAT would happen when it burns and you would ID it from there or two, you simply have to look at the sample under a microscope and compare signifying features to ID the fiber.
I'd say practice by looking at pictures online, like look up "cotton microscope view" or test it under your own microscopes.
Re: Crime Busters B
Posted: February 20th, 2019, 8:31 pm
by utumn
Was wondering how you can determine the speed of a vehicle based on its tire treads. I've already gotten the info for shoe prints, but I'm having trouble for the tire treads. Would it just be skid marks?
Re: Crime Busters B
Posted: February 21st, 2019, 4:16 am
by CPScienceDude
utumn wrote:Was wondering how you can determine the speed of a vehicle based on its tire treads. I've already gotten the info for shoe prints, but I'm having trouble for the tire treads. Would it just be skid marks?
I’ve never seen something like that on a test before, but maybe if there’s distortion in the tracks? I’m really not sure though.
Re: Crime Busters B
Posted: February 21st, 2019, 7:40 am
by starfruit
Re: Crime Busters B
Posted: February 22nd, 2019, 10:50 am
by Ocelot1912
Competition is soon, and I was wondering if you are allowed to touch the powders. Any replies are appreciated!
Re: Crime Busters B
Posted: February 22nd, 2019, 11:54 am
by SHASO2018
Out of curiosity, when did it change to 5 pages? When I was in Division B we were allowed to have a binder full.
Re: Crime Busters B
Posted: February 22nd, 2019, 12:07 pm
by CPScienceDude
Ocelot1912 wrote:Competition is soon, and I was wondering if you are allowed to touch the powders. Any replies are appreciated!
Yup, you're allowed to touch them.
SHASO2018 wrote:Out of curiosity, when did it change to 5 pages? When I was in Division B we were allowed to have a binder full.
Its actually down to one now, I'm not really sure when it changed, but it was 5 last year,
Re: Crime Busters B
Posted: February 22nd, 2019, 3:23 pm
by Crimesolver
CPScienceDude wrote:
Yup, you're allowed to touch them.
wait wat I thought that was illegal