Crime Busters B

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Re: Crime Busters B

Postby ashleybrown5 » December 2nd, 2017, 2:32 pm

How do you separate two powders that are mixed together? ex. baking soda and calcium carbonate

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Re: Crime Busters B

Postby shrewdPanther46 » December 2nd, 2017, 3:12 pm

ashleybrown5 wrote:How do you separate two powders that are mixed together? ex. baking soda and calcium carbonate

A good explanation for this is in the wiki. Generally, I just look for distinguishable properties from multiple powders.

I have a question pertaining to the analysis "questions" that are generally asked at the end. Is it necessary to write in full sentences, or can a list be presented? Most test have an open ended question and a bunch of lines underneath (like nationals). Could someone please let me know if a list could be used (mainly at higher level competitions) ? I am aware that this could vary between supervisors, but I would like to know the general consensus.

Thanks!
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Re: Crime Busters B

Postby SOCoach » January 1st, 2018, 6:18 am

Several years ago I bought a polymer / fiber kit for crimebusters that was really good. I can't seem to remember or find where I bought it from. Does anyone have a good site for getting fibers and plastics for crimebusters?

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Re: Crime Busters B

Postby knowthewrightstuff » January 2nd, 2018, 6:17 pm

My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

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Re: Crime Busters B

Postby shrewdPanther46 » January 2nd, 2018, 7:27 pm

knowthewrightstuff wrote:My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

You probs have some old, old peroxide. Spontaneous decomposition
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Re: Crime Busters B

Postby knowthewrightstuff » January 2nd, 2018, 11:46 pm

shrewdPanther46 wrote:
knowthewrightstuff wrote:My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

You probs have some old, old peroxide. Spontaneous decomposition

Thanks for the advice. We did notice that our bottle was expired last year so we bought a new bottle, but we still had the same problem. Do you just use a plastic test tube to shake it in?

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Re: Crime Busters B

Postby shrewdPanther46 » January 3rd, 2018, 4:45 am

We have glass, but its more or less the same.
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Re: Crime Busters B

Postby Tailsfan101 » January 3rd, 2018, 9:05 am

knowthewrightstuff wrote:My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

One way to tell them apart is to put some iodine in it. If it fizzes, it's hydrogen peroxide. If not, water.
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Re: Crime Busters B

Postby pikachu4919 » January 3rd, 2018, 10:53 am

SOCoach wrote:Several years ago I bought a polymer / fiber kit for crimebusters that was really good. I can't seem to remember or find where I bought it from. Does anyone have a good site for getting fibers and plastics for crimebusters?


The Society of Plastics Engineers sells a pretty comprehensive kit called Hands-On Plastics that has most everything except PMMA. A cheap way to get fibers is to go to the local craft/fabric store and see if they'll let you have 1-inch samples of fabrics for free or for really cheap.

Tailsfan101 wrote:
knowthewrightstuff wrote:My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

One way to tell them apart is to put some iodine in it. If it fizzes, it's hydrogen peroxide. If not, water.


I'm not sure how you got that to happen bc if you try to write a balanced equation for it, you won't get a product that will be in gaseous form.
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Re: Crime Busters B

Postby Unome » January 3rd, 2018, 11:52 am

pikachu4919 wrote:
Tailsfan101 wrote:
knowthewrightstuff wrote:My team has had trouble identifying the difference between water and hydrogen peroxide since they are both odorless and have the same pH. We have tried shaking them and looking for bubbles, but both liquids bubble for us. Are there other methods we could try to effectively identify the difference between these liquids?

One way to tell them apart is to put some iodine in it. If it fizzes, it's hydrogen peroxide. If not, water.


I'm not sure how you got that to happen bc if you try to write a balanced equation for it, you won't get a product that will be in gaseous form.

I found something on the H2O2/KI reaction here.
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Re: Crime Busters B

Postby pikachu4919 » January 3rd, 2018, 12:02 pm

Unome wrote:
pikachu4919 wrote:
Tailsfan101 wrote:One way to tell them apart is to put some iodine in it. If it fizzes, it's hydrogen peroxide. If not, water.


I'm not sure how you got that to happen bc if you try to write a balanced equation for it, you won't get a product that will be in gaseous form.

I found something on the H2O2/KI reaction here.


OK, I stand corrected... even so, I'm not entirely sure the gas released is always guaranteed to produce an audible fizzing sound like HCl + carbonate does? Even elephant toothpaste isn't that loud although it's a lot more pretty to watch XD
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Re: Crime Busters B

Postby Tailsfan101 » January 5th, 2018, 7:05 am

Does anyone know any easy ways to tell the difference between LDPE and HDPE? Those are the only plastics I've really been struggling with.
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Re: Crime Busters B

Postby pikachu4919 » January 8th, 2018, 8:07 pm

Tailsfan101 wrote:Does anyone know any easy ways to tell the difference between LDPE and HDPE? Those are the only plastics I've really been struggling with.


Your best bet is density, and that's at the mercy of your event supervisor to hopefully make something that's around 0.93-0.94 g/cm^3 since that's in the middle of the densities of HDPE and LDPE.
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Re: Crime Busters B

Postby Tailsfan101 » January 10th, 2018, 7:00 am

pikachu4919 wrote:
Tailsfan101 wrote:Does anyone know any easy ways to tell the difference between LDPE and HDPE? Those are the only plastics I've really been struggling with.


Your best bet is density, and that's at the mercy of your event supervisor to hopefully make something that's around 0.93-0.94 g/cm^3 since that's in the middle of the densities of HDPE and LDPE.

Thanks!
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Re: Crime Busters B

Postby pandascienceolympiad » January 12th, 2018, 3:47 pm

You have to also make sure that both of the substances are new and are not old. If they are old, they might not work


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