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Topic: Please help me identify this metal!!  (Read 2716 times)

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Offline The snake

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Please help me identify this metal!!
« on: March 01, 2016, 03:20:26 PM »
I am currently working on a metal identification lab, and am having a great deal of trouble with this sample. I have my thoughts about what it can be, but there's many things that negate my thoughts. Perhaps someone can identify the mistake in my thought process or even help me identify this sample. This is my first chemistry class, so please I apologize for any ignorance or stupid mistakes/misconceptions.

(PICTURES ATTACHED BELOW)

The given possibilities for the metal are:
Aluminum
Magnesium
Tin
Cobalt
Nickel
Titanium
Copper
Palladium
Zinc
Iron
Silicon
Lead
Silver
Nickel

Our sample did not show any magnetic properties, so we eliminated:
Cobalt
Nickel
Iron

Our sample did not react in Hydrochloric Acid, Ammonium Hydroxide, or Sodium Hydroxide (even when heated up over a bunsen burner), so we eliminated:
Magnesium
Tin
Aluminum
Zinc

We eliminated the following metals due to their clear difference in physical characteristics:
Copper
Lead

This leaves us with:
Titanium
Palladium
Silicon

We measured density at least ten times, and got results that ranged from 3.55 to 7.0, but removing those two outliers, the majority of the densities were in the 4's, with an average of 4.7. Since Titanium's density is 4.5, we were near certain it was Titanium, however we are having some problems with this theory:

1) We were able to melt our metal completely over the bunsen burner. Titanium's melting point is 1668C, but our research indicates that bunsen burners only go up to 1200-1400C. Shouldn't that mean that it can't be melted?
2) We were able to flatten our metal samples with a hammer. Perhaps this was because they weren't solid, but actually flakes. None the less, they were generally easy to bend, but also tore very easily. According to our research titanium is not malleable at room temperature. Shouldn't this mean that is is rock solid and can't be manipulated?
3) On only one out of three our trials with HCl, there was a vigorous bubbling reaction. The sample was untouched by sandpaper, though- so perhaps it was the outside coating?

Offline Arkcon

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Re: Please help me identify this metal!!
« Reply #1 on: March 01, 2016, 04:25:10 PM »
When you have results that  conflict like these, you have to realize that something you have done, is wrong, and everything is suspect.  So you may have to redo a test,or try to infer what was suspect, and disregard.  See if you can suggest some to disregard.  Some further thoughts:

3) On only one out of three our trials with HCl, there was a vigorous bubbling reaction. The sample was untouched by sandpaper, though- so perhaps it was the outside coating?

Now this bit of trivia is something that you might be able to use.  One of your options may have this property.  That can help.  However the whole "On only one out of three our trials" and furthermore:

Quote
We measured density at least ten times, and got results that ranged from 3.55 to 7.0, but removing those two outliers

I get that you may be a little new to chemistry and science, but something you should learn sooner or later is that you can't just remove an outlier that you don't like.  What you should do is not get an outlier like that at all.  That said,you can probably discount it, but it says you may not have done the measurement correctly even once.  So maybe that's one of the tests you won't use for your conclusion.


 
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline The snake

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Re: Please help me identify this metal!!
« Reply #2 on: March 01, 2016, 04:28:16 PM »
Thank you so much for your reply. You are right in all regards, if I had an opportunity to do this lab over again I would do things very differently.

Just based on the pictures, would you happen to have any suggestions as to what it can be?

Offline Burner

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Re: Please help me identify this metal!!
« Reply #3 on: March 01, 2016, 08:52:38 PM »
Sillicon is a semi-metal. Maybe testing electrical conductivity helps identify/rules out it.
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Offline P

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Re: Please help me identify this metal!!
« Reply #4 on: March 02, 2016, 05:29:27 AM »
You ruled out silver due to density? Maybe recheck the density if you were getting a range.
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Offline Arkcon

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Re: Please help me identify this metal!!
« Reply #5 on: March 02, 2016, 06:14:29 AM »
Thank you so much for your reply. You are right in all regards, if I had an opportunity to do this lab over again I would do things very differently.

Just based on the pictures, would you happen to have any suggestions as to what it can be?

See, here's where you have to make some decisions about what tests you like, and are secure about the way you've performed them, and can justify that in the lab report.  For example, you had some problems with the density test, and some ambiguity with the HCl test.  But could you possibly have failed to hammer it hard enough for the malleability test?  Conversely, with the crappiest camera possible, could you make the red color of copper metal wash out to that yellowish color we see on these boards?  Only you can answer those sorts of questions.

Look.  Very rarely, in real life, do we get lumps of metal to identify.  The point of this class is your critical thinking, and the justification for the same.  Technically, you get points if you luckily guess correct, but that may not work for you.  Whereas good application of logic will always save you from your own ambiguity.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Enthalpy

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Re: Please help me identify this metal!!
« Reply #6 on: March 02, 2016, 03:09:45 PM »
Titanium can be bent, rather easily when pure, and doesn't break.
Silicon is very brittle (glass-like), and anyway, it's darker than that.

Be cautious with "malleable" and "ductile", since many books put nonsense as a consequence of misconceptions instead of experimental knowledge. Zn for instance is malleable.

Some metals have a protective oxide layer: Cr, Al, Ti, Ta, Nb... which would make the reaction with acids hard to predict and possibly nonrepetitive.

Price should eliminate Pd.

Be somewhat careful with the magnetic properties. If your metals are reasonably pure it works, but ferromagnetism is a molecular property, not an atomic one, and for instance austenitic steel (Fe-Ni18-Cr8) is nonmagnetic while CrO2 is magnetic.

Offline Vidya

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Re: Please help me identify this metal!!
« Reply #7 on: March 03, 2016, 08:50:31 PM »
Thank you so much for your reply. You are right in all regards, if I had an opportunity to do this lab over again I would do things very differently.

Just based on the pictures, would you happen to have any suggestions as to what it can be?
From the pictures it appears like titanium only...

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