Can't Judge a Powder B

[2win]

D: well, i don't know about you guys, but we brought 3 graduated cylinders to every comp, and we never had any problems!

[haven chuck]

How would you say that the powder is a "powder" (as in, not crystalline)? Would it be sufficient to say that "the substance is not made of crystals"?

[rocketman1555]

How would you say that the powder is a "powder" (as in, not crystalline)? Would it be sufficient to say that "the substance is not made of crystals"?

You could write down everything that makes it so it isn't crystalline, such as the grains aren't cubes, stuff like that.

[ichaelm]

I just say things like "substance is not crystaline," "substance is not crushable," "substance has irregularly shaped grains," etc. Saying it's "not crystaline" isn't an inference, is it?

[poparteeb2]

Hey All,
I have some questions for the senior Can't Judge A Powder crew on here (I'm competing in Nationals for it).
Does anyone know how to describe a powder like flour? Because you would say salt is crystalline, but what would flour be?
Also, we have the basics for testing down but are there any obscure observations? Or what container the samples came in, or observations about the air?
Do we need to know a lot of chemistry? The state event was very easy, no real questions about chemistry. I've read on here you might have to know about polar compounds, free ions...anyone have a "survival guide" for this type of chemistry and how to test for it?
Thanks in advance.

[rocketman1555]

ichaelm: I would consider not crystalline as an inference, because there are ways that you can describe how the powder is not crystalline, such as: saying the grains don't have a regular shape, they don't have sharp edges, or the grains are not all the same shape/size.

poparteeb2: Flour would be amorphic. I would suggest that you know basic chemistry, such as types of bonds, the elements and their chemical symbol, and possibly basics about chemical equations.

[ichaelm]

If a solution contains free ions (aka it is an "electrolyte"), then it will conduct electricity.

Other chem stuff: know about hydrates, the chemistry behind pH, reaction energy, salts, etc...

There's really no limit to what they might ask. Read a chem book.

For obscure observations, just write absolutely everything you can think of. Maybe even come up with a list and memorize it somehow. I have a really really long mnemonic stuck in my head now lol.

[haven chuck]

ichaelm: I would consider not crystalline as an inference, because there are ways that you can describe how the powder is not crystalline, such as: saying the grains don't have a regular shape, they don't have sharp edges, or the grains are not all the same shape/size.

poparteeb2: Flour would be amorphic. I would suggest that you know basic chemistry, such as types of bonds, the elements and their chemical symbol, and possibly basics about chemical equations.

I think you could say it's "not made of crystals" in the same way that you could say that "there is no smell". You look and see that there are no crystals, so its strictly an observation.

[SolonSOohio]

I have some questions:
How do you tell if a powder is hygroscopic? (procedures)
How do you test conductivity if you aren't allowed to bring a multimeter? (tester used)

[haven chuck]

I have some questions:
How do you tell if a powder is hygroscopic? (procedures)
How do you test conductivity if you aren't allowed to bring a multimeter? (tester used)

A) Look in the 2007 test packet (2006 tests). There is an excellent description of the experiment that they were looking for testing for hygroscopic-ness on the CJAP test answer key.
B) Why wouldn't you be allowed to bring a multimeter? It says in the rules that a conductivity tester is allowed?