Crime Busters B

Test your knowledge of various Science Olympiad events.
MahathiR
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Re: Crime Busters B

Post by MahathiR »

1) Identical twins do not develop identical fingerprints because fingerprints are not controlled by as much by genetics as is the conditions of the womb.
2) Imbricate scales
3) pH test, as the two allowed powders that blacken in iodine are cornstarch and flour, and cornstarch typically has a higher pH
4) C
MahathiR
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Re: Crime Busters B

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My new questions:

1. Explain two types of fingerprint collection
2. Why does salt conduct electricity only when dissolved?
3. Lily is trying to figure out the components in a mixture, and is given the following description: An off-white, course powder mixed with a fine white powder, the mixture is partially soluble, and fizzes in HCl. What are the two components of this mixture?
4. Which plastics is recycled most often(give plastics from greatest to least)
Last edited by MahathiR on November 23rd, 2021, 10:31 am, edited 1 time in total.
aakoala
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Re: Crime Busters B

Post by aakoala »

Sorry for the month wait!
1. a) Dusting; you use brushes and dust it with a dark powder that sticks to sweat on the skin that has been transferred to a surface. You can then photograph the fingerprint and store it. b) Cyanoacrylate (superglue) fuming; put a fingerprint sample inside of a chamber and use cyanoacrylate fuming to attach to sweat on the sample. A picture of the fingerprint should appear.
2. I'm not completely sure, but since salt dissolves in water, it releases Na+ and Cl- ions which can conduct electricity?
3. The fizzing in HCl along with the fine white powder that might be soluble makes me think that this is Baking Soda. The off-white powder that doesn't dissolve but fizzes in HCl is indicative of Calcium Carbonate. I think it's baking soda and calcium carbonate.
4. I know PETE and HDPE are recyclable, so probably 1. PETE, 2. HDPE. Additionally, I know that LDPE and PS are not really recycled. Not sure about PP, so I'll put it in the middle. Final answer: 1. PETE, 2. HDPE. 3: PP, 4: LDPE, 5: PS
New questions:
1. Around how many ridges are on a fingerprint?
2. Would you expect the satellite+spine of a blood spatter to be longer with a low angle of incidence (close to the horizontal) or a high angle of incidence (close to the vertical)?
3. Classify each of the following fibers as extinguishing or non-extinguishing: Linen, Polyester, Wool
4. What is the densest Crime Busters metal?
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