Science Crime Busters B

[geekychic13]

Hi,
I saw a list if reactions to pretty much all powders, metals, etc., then the post got lost in history, the post was a table of sorts, and I really was hoping on this post to get me through the next 2 weeks until my competion. The post had the PH level, some comments like "fizzes with everything", or "changes color with ____". This is crucial information. If anyone could PLEASE help that would be VERY nice.
Regards,
DiscoLava

Look at the top right of your screen right now. You will see an orange bottle with three labels on it, and the word "Wiki" under it. Click on that. A new screen will pop up that says "Main Page." You will see three large columns. Under the one on the very left, click on crime busters (it's in the left column) if you scroll through the article about it, you will see that it includes the things you lost.

[willowmist]

How would you determine what unknowns make up a mixture, especially if there are two or three powders or crystals that are all similar?

[prelude to death]

Umm.. well, I'm not an expert on these things, since I only placed 3rd at Regionals, but the way that my partner and I identified them was (the day before the competition), we put together some powders that looked alike and that we thought would confuse us in the competition and we observed their reactions together. Oftentimes, if you know what some of the crystals look like (Ex. = salt and sugar), you'll be able to recognize the crysals after looking under a hand lens or something of the sort. Put HCl in the mixture and you could use process of elimination. All of the practice tests that I've taken have had cornstarch a lot (which is really uncanny >.>) so the way that I identify cornstarch is: put iodine into it, and it turns completely black. I believe that cornstarch is the only one that becomes completely black and undisturbed with iodine mixed with it, so there you've found one of your substances in the mixture. Then, try other things, like solubility in water and pH, although pH might be a little trickier if they've mixed two or more powders together really well. If the grains/powders are noticably different, you could try separating them just so that you can scoop them out onto reaction plates and then test them individually, although this method could take a little time. Try experimenting with your partner to see who's better at what and find out if any of you have an uncanny ability to identify mixtures.

[dholdgreve]

Umm.. well, I'm not an expert on these things, since I only placed 3rd at Regionals, but the way that my partner and I identified them was (the day before the competition), we put together some powders that looked alike and that we thought would confuse us in the competition and we observed their reactions together. Oftentimes, if you know what some of the crystals look like (Ex. = salt and sugar), you'll be able to recognize the crysals after looking under a hand lens or something of the sort. Put HCl in the mixture and you could use process of elimination. All of the practice tests that I've taken have had cornstarch a lot (which is really uncanny >.>) so the way that I identify cornstarch is: put iodine into it, and it turns completely black. I believe that cornstarch is the only one that becomes completely black and undisturbed with iodine mixed with it, so there you've found one of your substances in the mixture. Then, try other things, like solubility in water and pH, although pH might be a little trickier if they've mixed two or more powders together really well. If the grains/powders are noticably different, you could try separating them just so that you can scoop them out onto reaction plates and then test them individually, although this method could take a little time. Try experimenting with your partner to see who's better at what and find out if any of you have an uncanny ability to identify mixtures.

In addition to that, both cornstarch and flour are insoluble in water, making it very difficult to tell if the remaining powder is soluble or not... After you've determined that one of the components is either flour or cornstarch with iodine, place about 1cc of the sample in a test tube, and agitate well, now set it aside and allow it to settle for about 3 to 5 minutes. Now, without shaking it back up, add a few drops of HCl to the tube. If it fizzes immediately when it hits the water, you know that the remaining substance must be baking soda, because it dissolved in the water. If there is a delay on the fizz, it must be CaCO3, because it is insoluble, and settled to the bottom, taking the HCl longer to find it. No fizz at all could indicate the presence of CaSO4, assuming all of the mixture was powder, and not a mix of powder and crystal.

[megashrew64]

When I'm in crime busters, I just look at the salt/sugar up close. The salt is more cube-like, while the sugar is not. Try it yourself to come up with your own definition of the shape. I find it hardest to do the fiber and plastics, so if anyone has some tips there, I would love the advice!

[Arrowwolf]

Anyone's, and possibly everyone's, opinion on what was the hardest part and easiest part of this event.

[prelude to death]

Well, I don't know about you, but I find mixtures pretty hard. They're the ones that trick me up the most, so that's something that I let my partner do. However, fibers is also something that I'd rather give over to someone else. What I find the easiest is plastics, metals, and liquids, as well as the conclusion/short answer analysis questions. Honestly, the metals and liquids are pretty basic, and almost anyone could figure them out, but I tend to be quicker than my partner at identifying those. The powders are somewhat medium-ish to me, because some (like alka seltzer) are really noticeable and easy to identify with one drop of HCl, but others, (can't think of one off the top of my head) are a little harder. Mostly, it just depends on what you are the best at. Some things that your partner find easy might be a little more challenging to you. (But I guess the chromatography part is always really easy, huh?) So play off each others' strengths and weaknesses!

[megashrew64]

Yeah, no kidding. I couldn't even guess with the mixture, so I slapped down something at the last second. I found zinc extremely easy, along with most metal. I thought liquids were preety hard though. By the way, does this site have something against giving out what state we live in? I didn't know if I should put it in. Also, becasue I'm new, I would also appreciate it if someone could tell me what those stars are next to the name of the person posting the comment. Is it a gauge of how active they are?

[prelude to death]

Well, the liquids should be pretty easy, since vinegar and lemon juice have distinctive odors and are both acids. Ammonia should be the only base. If you've narrowed it down to hydrogen peroxide and water, then put a few drops of iodine into the solution. Identify other stuff while you're waiting, and after a while, some bubbles might appear. If they do, it means your unknown is hydrogen peroxide. If not, then it's water.

If you go to the User Control Panel, you can change your profile to change what state you live in. As for the stars, it's for post count. There's an old thread about it somewhere... I'll post it or PM you when I unearth it.

EDIT: It has been found. Hallelujah. http://scioly.org/phpBB3/viewtopic.php?f=25&t=2384

[Arrowwolf]

Thanks for the feed guys! Now I think i know what is to expect on Saturday for Regionals(I'm not sure when other peepz' regionals are but mine are this saturday)