Can't Judge a Powder B

[Cheesy Pie]

Look for obscure things. We were going through so much rigor testing that we didn't know the bag number, then we got that question. Don't get caught offguard.

[poparteeb2]

Just a clarification:

Exothermic would be when, say, your water was 19 degree Celsius, and then when you put the powder in, the solution/mixture whatever was 23 degrees Celsius. I guess it's because the solution releases heat?

Endothermic would be when your water was 19 degrees Celsius, and then when you put the powder in, the solution/mixture turned to 15 degrees Celsius. The energy would be potentially inside the mixture, right, so the solution would be colder?

Also, about whether the powder is hygroscopic or not: we put the powder out on a paper towel and see if it collects moisture at all. If it does, then it's hygroscopic. However, I'm kind of alarmed because a lot of you say that if it clumps, it's hygroscopic. Sometimes the powder is clumpy, but doesn't really get slushy or have water on it when put out on a paper towel. We thought that it wasn't hygroscopic, then.

Finally, about the event in powders in general: in our NY state event, the powder seemed to be amorphous under the naked eye, but then when put under a microscope, had crystals. Would it be okay to say that it was amorphous when looking, then say it had crystals under a microscope? Also, if a powder turns the liquid slightly cloudy or "milky" in color, then it would only be partly soluble, correct?

Last question: does anyone know if the proctor will take points off if you wrote inferences in your observations by mistake?

[robotman]

Just a clarification:

Exothermic would be when, say, your water was 19 degree Celsius, and then when you put the powder in, the solution/mixture whatever was 23 degrees Celsius. I guess it's because the solution releases heat?

Endothermic would be when your water was 19 degrees Celsius, and then when you put the powder in, the solution/mixture turned to 15 degrees Celsius. The energy would be potentially inside the mixture, right, so the solution would be colder?

Also, about whether the powder is hygroscopic or not: we put the powder out on a paper towel and see if it collects moisture at all. If it does, then it's hygroscopic. However, I'm kind of alarmed because a lot of you say that if it clumps, it's hygroscopic. Sometimes the powder is clumpy, but doesn't really get slushy or have water on it when put out on a paper towel. We thought that it wasn't hygroscopic, then.

Finally, about the event in powders in general: in our NY state event, the powder seemed to be amorphous under the naked eye, but then when put under a microscope, had crystals. Would it be okay to say that it was amorphous when looking, then say it had crystals under a microscope? Also, if a powder turns the liquid slightly cloudy or "milky" in color, then it would only be partly soluble, correct?

Last question: does anyone know if the proctor will take points off if you wrote inferences in your observations by mistake?

Both of your endo/exothermic things are correct

If a powder is clumped when they give it to you it is hygroscopic. I don't think that many powders would collect moisture in the few minutes you would leave it on a paper towel.. The Clumps are saying that it absorbed moisture in the container and congealed together.

As long as the powder doesnt settle out it will be partially soluble if the powder than settles out instead of staying suspended it will be insoluble

lastly yes points can be taken off for inferances if they are used for reasons on the test

[Cheesy Pie]

As robotman09 says, check the Wiki for some good ideas. (sorry if i offend you, robotman09.)

[poparteeb2]

Thanks guys!

Could you give an 'incorrect' observation, by any chance? (say the powder looks like it's amorphous but it's actually crystalline under a microscope).
Also, do you guys think it's worth it to do 1 g powder/5 ml of water, because that's the "5 point answer" in the rules?

[gneissisnice]

Thanks guys!

Could you give an 'incorrect' observation, by any chance? (say the powder looks like it's amorphous but it's actually crystalline under a microscope).
Also, do you guys think it's worth it to do 1 g powder/5 ml of water, because that's the "5 point answer" in the rules?

That must be a new rule, because it wasn't there when I did the event last (that was like 6 years ago). If it's in the rules, then yeah, I would definitely do it. The event tends to be so easy that every point counts.

[Cheesy Pie]

I think the no 120 volt batteries is kind of strange. I mean, who even uses 120 volt batteries?! But there should be a limit, even though it's amps not voltage that is harmful.

[robotman]

The 120 V thing is about not being allowed to have a conductivity tester that plugs into the wall not about battery limits >.>

[Cheesy Pie]

The 120 V thing is about not being allowed to have a conductivity tester that plugs into the wall not about battery limits >.>

Didn't know that. Thanks.

[Schrodingerscat]

I am personally surprised it was ruled against testing conductivity with multimeters this year. They can provide the most objective measure of the conductivity of a solution, as well as offering the compactness advantage over a battery light bulb, several batteries, and a bunch of wires.