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Can't Judge a Powder B

Posted: August 10th, 2014, 10:46 am
by Jim_R

Can't Judge a Powder

Posted: November 6th, 2014, 4:00 pm
by Kahler
I don't know how to find the density of a powder. Can anyone help me?

(This post was moved to the Can't Judge a Powder event forum - Mod)

Re: Can't Judge a Powder

Posted: November 7th, 2014, 3:39 pm
by asthedeer
Kahler wrote:I don't know how to find the density of a powder. Can anyone help me?

(This post was moved to the Can't Judge a Powder event forum - Mod)


The density of a powder is mass/volume. So far in the event (I did this event last year too), I haven't actually had to find the density of anything. Just be ready to answer questions about relative density, such as "Is the powder more dense/less dense than ____ (name of reagent)?" In that case, you could stick in as an answer something like- "Observation ##: The powder sinks in/floats in ____ (same name of reagent) , therefore, the powder is more dense/less dense than ____(reagent)"

HIH,
~asthedeer~

Re: Can't Judge a Powder

Posted: November 11th, 2014, 7:32 am
by cupcakegirl
Kahler wrote:I don't know how to find the density of a powder. Can anyone help me?

(This post was moved to the Can't Judge a Powder event forum - Mod)

If they give you a balance and a graduated cylinder, then you can find it. This explains it nicely:
http://www.newton.dep.anl.gov/askasci/c ... m03532.htm
It's a pretty rare question (like asthedeer said), but I have seen it before. Good luck!

Re: Can't Judge a Powder

Posted: November 13th, 2014, 11:58 am
by samlan16
Kahler wrote:I don't know how to find the density of a powder. Can anyone help me?

(This post was moved to the Can't Judge a Powder event forum - Mod)


Basically you need to start by taking the mass of the sample. I recommend taking the mass of the sample and the container first, then pouring it into a different container to mass the original container. You can subtract the two to get the mass of the sample, and that counts as another observation. (WARNING: Do not only give the mass of the sample. That is an inference.) Then, find the volume of the sample by measuring the volume in a beaker. As another observation, divide the mass by the volume. I recommend rounding to 2 decimal places. The SI unit is g/cm^3 or g/mL. Be certain that this is how you measure everything.

Re: Can't Judge a Powder

Posted: November 15th, 2014, 5:35 pm
by asthedeer
cupcakegirl wrote:
Kahler wrote:I don't know how to find the density of a powder. Can anyone help me?

(This post was moved to the Can't Judge a Powder event forum - Mod)

If they give you a balance and a graduated cylinder, then you can find it. This explains it nicely:
http://www.newton.dep.anl.gov/askasci/c ... m03532.htm
It's a pretty rare question (like asthedeer said), but I have seen it before. Good luck!


Unless I'm mistaken, you aren't allowed to bring graduated cylinders in competitions tho....

Re: Can't Judge a Powder B

Posted: November 27th, 2014, 8:14 am
by Moxyfinkle
Unless I'm mistaken, you aren't allowed to bring graduated cylinders in competitions tho....

She means if they give you a graduated cylinder. You're right, you can't bring one yourself, which is why it's not always asked about.

Re: Can't Judge a Powder B

Posted: November 27th, 2014, 9:22 am
by asthedeer
Ah I see. :P I didn't notice the "if they give" part. :D

Re: Can't Judge a Powder B

Posted: December 2nd, 2014, 2:33 pm
by Boombloxer2
asthedeer wrote:Ah I see. :P I didn't notice the "if they give" part. :D


Ya Suuurreeeeeee

Re: Can't Judge a Powder B

Posted: December 15th, 2014, 7:13 pm
by Madian
Hello, I was just wondering if any of you had any specific suggestions on how to make observations. Also, should we keep referring back to the solution on every observation after or not?
Thanks!

Re: Can't Judge a Powder B

Posted: December 16th, 2014, 9:15 am
by asthedeer
No specific way as far as I know. I do believe though, that they like organized observations. For example, I wouldn't do an observation about the color of the powder for #1, then have another observation such as "The HCl conducts electricity" for #2, but instead put all the observations about the powder in, say, the first 10 observations.
I'm not sure what you mean by "referring back to the solution". Does it mean looking at the solution for everything you write?

Re: Can't Judge a Powder B

Posted: December 16th, 2014, 10:34 am
by dholdgreve
A few suggestions from one that has run this event for several years:
* Each observation should stand on it's own... don't assume that because the observation prior was with an aqueous solution, that I will assume that this is as well... I won't.
* Pronouns are rarely a good thing in this event... Better to take the extra few seconds and write it out.
* This event boils down to giving a better observation than your competition... Look at it as being graded on a curve... Try to structure your observations to be both quantitative as well as qualitative
* Find ways to make your observations just a little better than the competitions by using adjectives that better describe what you observed
* Yes, abbreviations theoretically are allowed, if defined somewhere on the page, but is it worth the risk? If we are grading 50 tests in as little as an hour, it is very easy to miss the abbreviation key... I would not risk it
* The intent means nothing if I can't read what you've written... I'll give you every possible benefit, but if I can't read it, I can't give you credit. Decide if you or your partner have the neatest hand writing, and have that one do the recording
* In every test, there will probably be at least 1 question that you did not record an observation for - Yes, you are allowed to write in an answer, but it should be in form of an observation; complete and whole (i.e substance was soluble in
water...not "yes")

Re: Can't Judge a Powder B

Posted: December 18th, 2014, 11:00 am
by samlan16
To any coaches out there: we got our school's CJAP tests back from an invitational, and our teams lost points because they answered questions with more than 3 observations. When I competed in this event in B division, there was no such rule. Did the proctors goof, or is this a legitimate rule now that I missed when reading the rules?

Re: Can't Judge a Powder B

Posted: January 2nd, 2015, 12:52 pm
by robotarmy567
does anyone know what a "pure substance" is :?

Re: Can't Judge a Powder B

Posted: January 3rd, 2015, 5:25 pm
by Moxyfinkle
samlan16 wrote:To any coaches out there: we got our school's CJAP tests back from an invitational, and our teams lost points because they answered questions with more than 3 observations. When I competed in this event in B division, there was no such rule. Did the proctors goof, or is this a legitimate rule now that I missed when reading the rules?
It's not an official rule, but some proctors (especially at invitationals) do place a limit on the number of observations you can answer a question with. They're supposed to tell the teams if they do that though. It's best not to put down more than 3 observations unless absolutely necessary.I think the nats proctor also had that same limit, but correct me if I'm wrong.