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Physical Change vs. Chemical Change?


Q. Physical or Chemical Change:
Silver nitrate [on eBay or Amazon] reacts with copper to form silver on the surface of the copper.

I am in 11th grade.

Laura N [last name deleted for privacy by Editor]
Student - New Brunswick, New Jersey USA
October 27, 2010


A. Hi, Laura. I've heard many definitions/explanations of physical vs. chemical change, but one that I really like says "a chemical change isn't easily undone".

To be sure, it's not always easy to undo a physical change, as we learn when we get an estimate from the body shop -- but I think the point of that definition is to get you to think about what you would need to do to "undo" the deposition of silver metal onto copper and get that silver back into solution as silver nitrate.

Could you do physical changes that would undo it? I don't think so. I realize that this definition can result in a bit of circular reasoning, further compounding the question ("a chemical change is a change that requires another chemical change to undo"). I guess this perversity in the explanation is what makes me like it :-)

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


A. I'll admit it's been a while since I last checked the student section, but it is just me or is the level of effort at disguising homework actually decreasing? :)

Laura, you didn't even TRY to make it sound like you are doing a science project or something - you may as well have fully gone for it a wrote "Question 21: Physical or Chemical change..."

I must say that I like Ted's definition of a chemical change... the problem is that it makes so many social interactions fall into the category!

Jim Gorsich
Compton, California, USA


thumbs up sign Hi, Jim. Great point. Once it's been said or seen, it's been said or seen :-)

rubaiyat
"The Moving Finger writes; and, having writ,
Moves on: nor all your Piety nor Wit
Shall lure it back to cancel half a Line,
Nor all your Tears wash out a Word of it."
    - The Rubaiyat of Omar Khayyam

I wonder ...

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


"Alike for those who for TO-DAY prepare,
And that after a TO-MORROW stare,"

Introducing me to that poem is simply one more thing I am grateful to you for, Ted.

Jim Gorsich
Compton, California, USA


thumbs up sign Thanks for the verse, Jim. I always greatly appreciate your efforts, and thank you your unrealistically kind appraisal of mine.

Readers can see The Rubyiat here, and they will quickly take something profound from it -- but whether it is to live passionately, thinking only of TO-DAY, or to prepare for a very long TO-MORROW, I don't know. Thought provoking it is, and trite it isn't :-)

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey




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