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Topic: Is this right of a teacher?  (Read 11463 times)

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Offline DarkLightA

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Is this right of a teacher?
« on: November 20, 2009, 11:42:53 AM »
I'm doing chemistry in 8th grade for the first time ever, and my teacher doesn't know everything.. Hrm hrm..

He says:
Al + HCl ==> AlCl + H
Is it normal that teachers say this to new students in order to not confuse them? It seems a bit weird, as I spent about 2-3 hours online to develop a method of finding that it's actually:
Al2(m) + 6HCl(aq) ==> 2AlCl3(s) + 3H2(g)

Well, I guess I'm smart, but shouldn't students be taught the right thing from the start?

Kind regards,
"DLA"

Offline DrCMS

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Re: Is this right of a teacher?
« Reply #1 on: November 20, 2009, 11:57:55 AM »
Did the your teacher write that equation or did they say "Aluminium reacts with Hydrochloric acid to give Aluminium Chloride and Hydrogen"?

Offline Borek

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Re: Is this right of a teacher?
« Reply #2 on: November 20, 2009, 12:42:09 PM »
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline DarkLightA

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Re: Is this right of a teacher?
« Reply #3 on: November 20, 2009, 12:44:31 PM »
Did the your teacher write that equation or did they say "Aluminium reacts with Hydrochloric acid to give Aluminium Chloride and Hydrogen"?

My teacher has taught us to do it that way, in written form. I once asked why it said Ca + 2HCl ==> CaCl2 + H2 on a hand-out instead of Ca + HCl ==> CaCl + H which we'd learnt. He said "Just ignore that" and left. That's what started my interest in this, and now I think I'm into 9th grade stuff, so at least there was something positive about him  ::)

---

@Borek: of course, I slipped with thinking (m) for metal =)
Is it Al2 of 2Al?

Offline nj_bartel

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Re: Is this right of a teacher?
« Reply #4 on: November 20, 2009, 12:50:23 PM »
Blegh, I hope that isn't what your teacher does.  Balancing nonredox equations is not too difficult to start from the get go.

Offline DarkLightA

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Re: Is this right of a teacher?
« Reply #5 on: November 20, 2009, 12:54:12 PM »
Blegh, I hope that isn't what your teacher does.  Balancing nonredox equations is not too difficult to start from the get go.

The problem is that he doesn't know how to do it himself...  :-\

Offline renge ishyo

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Re: Is this right of a teacher?
« Reply #6 on: November 20, 2009, 01:37:49 PM »
A lot of times in high schools there is such a shortage of science teachers that they have teachers who do not have a degree in science teaching science (they have to take science courses as part of their credential package which supposedly "qualifies" them to teach it, but sadly this doesn't mean they did well in those courses). This seems like one such case.

To the TC, now you know how he is handling it, so do what you can to follow your textbook and online sources so that you can build an undamaged knowledge for yourself. The teacher might innocently think to himself, "well what is the difference?", and so he thinks he is making the idea simpler, but the way the teacher is teaching it ignores the concept of valence (which is why you need multiple chlorines for instance; it is to balance the +3 valence on aluminum). This is obviously something you don't want to do if you plan to go further in chemistry in the future (something the teacher might be assuming you don't want to do because perhaps he doesn't like it?).

However, a word of advice TC, on the test  give the teacher the answer that he taught you in class and don't point out his mistakes to him any longer. It is a general rule that the less someone knows about something the more apt they are to viciously defend their ignorance when challenged. If you pointed it out to him once already and he ignored you, don't point it out again. Instead just make do and pass the class. Hopefully you will get a teacher that conforms closer to the accepted standards the next time around.

EDIT: Well, in thinking about it maybe I was a bit too harsh here. We do not know the context of the class, and maybe the teacher wants to introduce some sample reactions first and then balance them at a later point? It is not the way I would do things (he could use reactions like NaOH + HCl  :rarrow: H2O + NaCl that are simple enough and are viable chemical equations at the same time), but so long as he intends to make things right eventually (one would hope) I guess it isn't overtly wrong to do it this way. The equation Al + HCl  :rarrow: AlCl + H does describe an experimental fact, it just is not considered a valid chemical equation until it is balanced. That is the only difference between the two statements. At least he isn't doing Al + HCl  :rarrow: NaOH. I mean, it could be worse...
« Last Edit: November 20, 2009, 02:08:34 PM by renge ishyo »

Offline renge ishyo

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Re: Is this right of a teacher?
« Reply #7 on: November 20, 2009, 02:21:09 PM »
I guess DarkLightA's other post on valence answered that (didn't see that first). Your teacher is forgiven I guess for the whole 3 hours of confusion he caused you  ;)

Offline DarkLightA

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Re: Is this right of a teacher?
« Reply #8 on: November 20, 2009, 03:20:57 PM »
I guess DarkLightA's other post on valence answered that (didn't see that first). Your teacher is forgiven I guess for the whole 3 hours of confusion he caused you  ;)

What do you mean? That stuff is self-learned online :)

Offline renge ishyo

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Re: Is this right of a teacher?
« Reply #9 on: November 20, 2009, 03:38:39 PM »
Quote
What do you mean? That stuff is self-learned online

Way to kill my temporarily restored faith in our high school education system  :'(

Offline DrCMS

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Re: Is this right of a teacher?
« Reply #10 on: November 20, 2009, 04:05:00 PM »
Did the your teacher write that equation or did they say "Aluminium reacts with Hydrochloric acid to give Aluminium Chloride and Hydrogen"?

My teacher has taught us to do it that way, in written form. I once asked why it said Ca + 2HCl ==> CaCl2 + H2 on a hand-out instead of Ca + HCl ==> CaCl + H which we'd learnt.

If I am reading this correctly the teacher has been teaching you in written form and you have been writing it down in equation form.

So your teacher said "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
and so you wrote that down incorrectly as "Ca + HCl  :rarrow: CaCl + H"

Later the teacher gave you a hand out saying "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
giving the reaction correctly as "Ca + 2HCl  :rarrow: CaCl2 + H2"

If that is the case it is you that is causing the confusion by trying to be too clever and failing.

Offline DarkLightA

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Re: Is this right of a teacher?
« Reply #11 on: November 20, 2009, 04:13:56 PM »
So your teacher said "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
and so you wrote that down incorrectly as "Ca + HCl  :rarrow: CaCl + H"

Later the teacher gave you a hand out saying "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
giving the reaction correctly as "Ca + 2HCl  :rarrow: CaCl2 + H2"

If that is the case it is you that is causing the confusion by trying to be too clever and failing.

No, we've been taught both word equations and symbol equations. The teacher writes it on the board like that (incorrectly), and I write it down and go on google when I come home and disprove it to myself and learn the real thing  :-\

Offline DarkLightA

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Re: Is this right of a teacher?
« Reply #12 on: November 20, 2009, 04:14:36 PM »
Quote
What do you mean? That stuff is self-learned online

Way to kill my temporarily restored faith in our high school education system  :'(

Any time  ;)

At least the internet is good..

Offline DrCMS

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Re: Is this right of a teacher?
« Reply #13 on: November 20, 2009, 04:23:38 PM »
So your teacher said "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
and so you wrote that down incorrectly as "Ca + HCl  :rarrow: CaCl + H"

Later the teacher gave you a hand out saying "calcium reacts with hydrochloric acid to give calcium chloride and hydrogen"
giving the reaction correctly as "Ca + 2HCl  :rarrow: CaCl2 + H2"

If that is the case it is you that is causing the confusion by trying to be too clever and failing.

No, we've been taught both word equations and symbol equations. The teacher writes it on the board like that (incorrectly), and I write it down and go on google when I come home and disprove it to myself and learn the real thing  :-\

OK sorry, this means your teacher is crap (or you need glasses)

Offline renge ishyo

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Re: Is this right of a teacher?
« Reply #14 on: November 20, 2009, 04:37:16 PM »
If I didn't live in California (49th out of 50 in the nation at last count in high school education!), and if I didn't see and experience how people are being taught here I wouldn't believe it.

This reminds me of the time I had a student come to me for help in Chem 101 when I worked as a tutor, and she angrily claimed that her teacher wasn't teaching them anything. So I did my usual "it is your responsibility to learn the material, show up to class every day, and listen to the lecture, yadda yadda," but then I had to bite my tongue when the student told me that "there was no lecture to listen to." Huh? It turns out what the teacher was doing was handing the students packets of problems and putting them in groups to "teach each other" as part of a new experimental "hands off" approach to teaching students. The student was almost finished with a year course in chem 101, and she didn't even know what an atom was. It was truly a sad thing to see.

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