AKICILJ: state standards

[redbird]

We're back to reading the mind of a committee. In this case, I have a state standard (Tennessee, in case you care) that says students should be able to "Identify the common outcome of all chemical changes."

What does this mean? My best guess is conservation of mass, except that's explicitly listed later on. Maybe that the identity of the substance changes?

Comments

[liv]

Er, bonds are either formed or broken? Almost everything I can think of seems circular, though. Chemical changes have the common property that some chemical is changed, no duh!

[timill]

Common as in usual??

[cantkeepsilent.livejournal.com]

I'll guess that it has something to do with the difference between "chemical changes" and "physical changes", whatever those are. I'd guess that you're right that the key is that you wind up with different substances, and maybe also that there is probably going to be a change in the heat of the system one way or the other.

That's more or less it

[akicif.livejournal.com]

The phrasing of the question's not brilliant, but I think you've got it: in a chemical reaction, a new substance is formed which has a different arrangement of atoms from the reactants (as you say, the change in the heat of the system could go either way - or be arbitrarily small).

[zingerella.livejournal.com]

There are some very very strange state science standards. Some of them make good sense, and seem to have been crafted by people who understood both science and the teaching thereof. Others ... not so much. I haven't been keeping a list of the odd ones -- I just kind of roll my eyes and e-mail my senior editor with a "Do you think [[bit of content]] meets [[standard]]? I'm not sure!"

Do they perhaps mean the usual indications that a chemical change has taken place (change in state, change in colour, change in temperature, etc?)

[akicif.livejournal.com]

Unlikely - you can get all of those concurrent with simple physical change.

[zingerella.livejournal.com]

Sorry. You're right. My brain is full of hagfish slime today.

[akicif.livejournal.com]

Lovely image....

I'm thinking now, though, that the change of colour in melting sulphur may actually involve a chemical change when S₈ rings break up.

[zingerella.livejournal.com]

You know it's going to be a great Monday when the first thing you have to do, on reaching the office, is research hagfish slime.

I'm remembering, very hazily, from first-year chem, a list of things that happened that denoted a chemical, rather than a physical change, but perhaps that list was particular to when two solutions were mixed together: they could change colour, or there could be a precipitate, or they could fizz (either of those last would be state changes, of course), or one might smell something as a gas was produced (another state change). It has been many years, and I was not a very good chemistry student, so I am very likely misremembering.

[redbird]

I think there's a different piece of the standard that talks about signs of chemical change.

[webbob.livejournal.com]

Reduction of the total internal energy of the participating reactants. Release of free energy, in other words.

[akicif.livejournal.com]

You can have endergonic reactions with a positive ΔG - they're just not spontaneous.

[webbob.livejournal.com]

Rats.

[adrian-turtle.livejournal.com]

Do you think this was written by a sufficiently coherent person as to actually be talking about the "common outcome" in the sense of "the outcome all such changes have in common?" I know people who could start with "Identify common chemical changes and describe what they have in common," attempt to make the sentence shorter and more sophisticated, trip over their underpants, and come out with something like your original problem.

[redbird]

I don't know whether it was written by a person, and committees aren't good at coherence. (This one, at least, seems mostly to have been written by one committee, and I think they may have set foot in the same building at the same time.) I think "in common" is more likely than common as distinct from rare.

[avram]

Is it possible they meant "Identify the outcomes of all common chemical changes"? Like, maybe they've got a list of common chemical interactions and the student's supposed to be able to describe them all?

[redbird]

If so, that is way beyond what we can cover, given the amount of space we have to work with and the fact that the list is not supplied.

[calimac.livejournal.com]

As this is Tennessee, "the common outcome of all chemical changes" probably is intended to mean "evidence for Intelligent Design." Sigh.