Page 11 of 25
Re: Can't Judge a Powder B
Posted: March 30th, 2011, 3:39 pm
by EpicFailure
Can anyone with a lot of experience in this event tell me how you split up the test? Like, some sources say that you should have both people test at the same time (1 person doing raw powder+other liquids and the other person doing aqueous solution of powder+other liquids). During our practice sessions, my partner and I just had one person write and the other do all the testing. Which way do you think is better? Also, is it necessary to test aqueous solution+other liquids if the powder isn't soluble in water?
Re: Can't Judge a Powder B
Posted: March 30th, 2011, 7:35 pm
by Cheesy Pie
I have really messy handwriting but almost-OCD when it comes to measuring the right amounts. My partner has neater handwriting, so she wrote it out while I did the testing.
To answer your other question, just say it wasn't soluble! Don't go through the torture of trying to test what cannot be tested.
Re: Can't Judge a Powder B
Posted: March 31st, 2011, 3:56 pm
by geekychic13
robotman09 wrote:geekychic13 wrote:what do you mean when you say it will absorb ambient water?
robotman09 wrote:whether or not it clumps.
If it is clumped in the container they give you of it it would obsorbe ambient H2O
It was a reference to the definition of Hygroscopy
dholdgreve wrote:tying15 wrote:What does hygroscopic mean?
Hygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment through either absorption or adsorption with the adsorbing or absorbing material becoming physically 'changed,' somewhat: by an increase in volume, stickiness, or other physical characteristic of the material as water molecules become 'suspended' between the material's molecules in the process. While some similar forces are at work here, it is different from capillary attraction, a process where glass or other 'solid' substances attract water, but are not changed in the process, e.g. water molecules becoming suspended between the glass molecules.
Okay... I didn't know what ambient meant, but I knew what hygroscopy meant thanks
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 3:32 pm
by Zest
Does anyone know... What are the best testing materials to use and be organized? Beakers? Spot plates? Test tubes?
Also, is having a stirring rod or spatula crucial?
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 3:38 pm
by robotman
I suggest spot plates mainly because it forces you to use a small amount of powder and reagent and also saves time and space instead of having 6 beakers you would have one spot plate.
I personally think that having both a stirring rod and spatula is crucial, however you can use a spatula as both if you get the right one
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 3:49 pm
by Zest
what does it mean if a substance disolves endothermically or exothermically?
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 3:52 pm
by Zest
which type of spatula would be the right one?
Also, how would you measure how much of the powder you use in the sample?
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 3:58 pm
by Schrodingerscat
Zest wrote:what does it mean if a substance disolves endothermically or exothermically?
Endothermic reactions means it takes more energy to form the bonds of the products than the bonds broken in the reactants, absorbing heat. This can be observed by a decrease in temperature.
Exothermic reactions means it takes less energy to form the bonds of the products than the bonds broken in the reactants, giving off heat. This can be observed by an increase in temperature.
Another way to describe this is endothermic releases less energy than the activation energy and exothermic releases more.
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 6:23 pm
by Zest
ok, thanks,
so the only way to test this is if you have a thermometer and we aren't allowed to briing it, so it dpends if the supervisor provides it?
Re: Can't Judge a Powder B
Posted: April 3rd, 2011, 6:25 pm
by robotman
Zest wrote:which type of spatula would be the right one?
Also, how would you measure how much of the powder you use in the sample?
Well it would be one that has a flat side for powder scooping and another rounded end for stirring
Zest wrote:ok, thanks,
so the only way to test this is if you have a thermometer and we aren't allowed to briing it, so it dpends if the supervisor provides it?
you might be able to tell my feeling the spot plate if there is a massive change