Crime Busters B

[imaditi]

I've been having trouble finding the reactions of the white powders and potassium iodide. I really have no way to test them out myself, so can someone help me out?

If you want to differentiate flour and cornstarch, flour is an off white and also clumps together in water. Also Alka Seltzer fizzes in everything.

[NewSciolyer]

I think my coach told us the day before our invitationals that they wanted to make clarification on the rules. I think you're only allowed one sheet of paper, not two.

[wec01]

I think my coach told us the day before our invitationals that they wanted to make clarification on the rules. I think you're only allowed one sheet of paper, not two.

The same wording was used for forensics last year and 2 sheets were allowed at competition, so most likely that’s what they intended.

[NewSciolyer]

Ah, so two sheets of paper but they have to contain the same information?

[NewSciolyer]

I am having trouble differentiating Animal, Vegetable, and synthetic fibers. It seems like different types of vegetable fibers react differently to flame test and overall it is really confusing to discern the different types of fibers. How do you properly do a burn test and tell what kind of fiber it is? Is there any other ways that you can tell besides burning them? I can't seem to find any straightforward sources on the internet. Thanks.

[FiveW's]

I am having trouble differentiating Animal, Vegetable, and synthetic fibers. It seems like different types of vegetable fibers react differently to flame test and overall it is really confusing to discern the different types of fibers. How do you properly do a burn test and tell what kind of fiber it is? Is there any other ways that you can tell besides burning them? I can't seem to find any straightforward sources on the internet. Thanks.

I'm also still learning the event, but other than burn tests one way you can tell them is looks and feel. Synthetic will normally be smooth. And depending on supervisor Cotton is sometimes unprocessed so it will be rougher. I do highly recommend doing the burn tests though because those are the biggest signs. Things to look for in burn tests really are speed, smell, and looks with those three you should be able to differentiate.

[SilverBreeze]

I am having trouble differentiating Animal, Vegetable, and synthetic fibers. It seems like different types of vegetable fibers react differently to flame test and overall it is really confusing to discern the different types of fibers. How do you properly do a burn test and tell what kind of fiber it is? Is there any other ways that you can tell besides burning them? I can't seem to find any straightforward sources on the internet. Thanks.

I'm also still learning the event, but other than burn tests one way you can tell them is looks and feel. Synthetic will normally be smooth. And depending on supervisor Cotton is sometimes unprocessed so it will be rougher. I do highly recommend doing the burn tests though because those are the biggest signs. Things to look for in burn tests really are speed, smell, and looks with those three you should be able to differentiate.

Hello, I did this event in Div. B.

For differentiating fibers by flame test, animal smells like burning hair(that's pretty much what it is), synthetic will melt and create a sweet or acrid smell like a plastic(that's what it is), and plant will burn cleanly like a candle wick or a bomb fuse.

Feel is another way, but often proctors will set up microscope stations and allow participants to look at the fibers under a microscope. Often, they will simply put an image on the test. The best way to prepare for this is to search up various images of plant, animal, and synthetic fibers and perhaps put them on your cheatsheet.
Plant fibers are usually cotton or linen. Cotton looks like flattened strips, and linen looks like bamboo or stacked cups.
Animal fibers look like hairs, with a medulla, cortex, and cuticle. Silk is the exception. It looks synthetic, but will tend to be more irregular.
Synthetic fibers are smooth and uniform. They typically have little variation along the strand.

[jslocum]

Hi all,

I'm a coach purchasing chemicals for my students and we've run across an issue. According to the resources on the Sci Oly site, Calcium Carbonate reacts with HCl, and Calcium Sulfate (Gypsum) does not. I purchased Calcium Carbonate and Calcium Sulfate both from Ward Science. My students were having trouble separating them because they both reacted with HCl. My first assumption was that they contaminated the Calcium Sulfate so I bought new Calcium Sulfate from Ward Science, but the results remained the same. The Calcium Sulfate reacted with HCl also. Upon closer inspection of the Calcium Sulfate bottle, there is a note that says "Contains: Calcium Carbonate".

So, I have a few questions...
- am I buying the wrong stuff?
- where would I get the correct Calcium Sulfate (Gypsum)
- do you think other supervisors are getting Calcium Sulfate from Ward Science, possibly throwing off the results of their competitions.

Please enlighten me!

[SilverBreeze]

Hi all,

I'm a coach purchasing chemicals for my students and we've run across an issue. According to the resources on the Sci Oly site, Calcium Carbonate reacts with HCl, and Calcium Sulfate (Gypsum) does not. I purchased Calcium Carbonate and Calcium Sulfate both from Ward Science. My students were having trouble separating them because they both reacted with HCl. My first assumption was that they contaminated the Calcium Sulfate so I bought new Calcium Sulfate from Ward Science, but the results remained the same. The Calcium Sulfate reacted with HCl also. Upon closer inspection of the Calcium Sulfate bottle, there is a note that says "Contains: Calcium Carbonate".

So, I have a few questions...
- am I buying the wrong stuff?
- where would I get the correct Calcium Sulfate (Gypsum)
- do you think other supervisors are getting Calcium Sulfate from Ward Science, possibly throwing off the results of their competitions.

Please enlighten me!

Usually, calcium sulfate is sold as plaster of Paris, which bubbles slightly in both water and HCl, but doesn't make the fizzing sound calcium carbonate and sodium bicarbonate make. Calcium carbonate is used in construction, so the two are often mixed. Have you tried searching for powdered gypsum, which is another form of calcium sulfate? I've read some chalk is made from calcium sulfate instead of calcium carbonate, but I don't know how readily available that is. If event supervisors use calcium sulfate mixed with calcium carbonate, the powder in water or HCl with harden after about five minutes, which is how we used to differentiate it. Calcium sulfate is not supposed to react with anything if pure.

[dholdgreve]

Hi all,

I'm a coach purchasing chemicals for my students and we've run across an issue. According to the resources on the Sci Oly site, Calcium Carbonate reacts with HCl, and Calcium Sulfate (Gypsum) does not. I purchased Calcium Carbonate and Calcium Sulfate both from Ward Science. My students were having trouble separating them because they both reacted with HCl. My first assumption was that they contaminated the Calcium Sulfate so I bought new Calcium Sulfate from Ward Science, but the results remained the same. The Calcium Sulfate reacted with HCl also. Upon closer inspection of the Calcium Sulfate bottle, there is a note that says "Contains: Calcium Carbonate".

So, I have a few questions...
- am I buying the wrong stuff?
- where would I get the correct Calcium Sulfate (Gypsum)
- do you think other supervisors are getting Calcium Sulfate from Ward Science, possibly throwing off the results of their competitions.

Please enlighten me!

Usually, calcium sulfate is sold as plaster of Paris, which bubbles slightly in both water and HCl, but doesn't make the fizzing sound calcium carbonate and sodium bicarbonate make. Calcium carbonate is used in construction, so the two are often mixed. Have you tried searching for powdered gypsum, which is another form of calcium sulfate? I've read some chalk is made from calcium sulfate instead of calcium carbonate, but I don't know how readily available that is. If event supervisors use calcium sulfate mixed with calcium carbonate, the powder in water or HCl with harden after about five minutes, which is how we used to differentiate it. Calcium sulfate is not supposed to react with anything if pure.

WOW! That IS alarming! My kids have been coming back saying "But it fizzed!" To which I responded "It couldn't!" ... Now we see why! No, there should not be any calcium carbonate in the Calcium Sulfate material. Maybe try doing a search for Calcium Sulfate Dihydrate, or as previously suggested, Gypsum. I think I actually bought mine in a foil bag from ebay.