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Topic: Chemical vs Physical Change  (Read 10164 times)

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Offline antoinetta

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Chemical vs Physical Change
« on: September 10, 2006, 08:57:06 PM »
Hello, I seem to have trouble differentiating between chemical vs physical change for the following:  Would somebody mind checking my responses?

i) toaster filament becomes red hot - physical
ii) grease spot is dissolved with cleaning fluid - chemical
iii) heated oil turns brown - chemical
iv) alkaline flashlight battery discharges - chemical

The oldest, shortest words - "yes" and "no" are those which require the most thoughts.  - Pythagoras

Offline P-man

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Re: Chemical vs Physical Change
« Reply #1 on: September 10, 2006, 09:00:25 PM »
It looks correct  :).
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Offline Korokian

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Re: Chemical vs Physical Change
« Reply #2 on: September 10, 2006, 09:12:20 PM »
looks good to me....

Offline constant thinker

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Re: Chemical vs Physical Change
« Reply #3 on: September 10, 2006, 09:34:56 PM »
That's a hard concept to kind of explain. All one can really say about it is, a chemical change involves the change of a molecule and you can apply a chemical formula. A physical change is something that doesn't change the molecule.

Also chemical changes happen at the micro level while physical changes usually happen at the macro level.

O, and your things are right.
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Offline Donaldson Tan

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Re: Chemical vs Physical Change
« Reply #4 on: September 10, 2006, 09:42:31 PM »
Macroscopic description of a chemical change is that it involves a change in composition in a close system.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline Yggdrasil

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Re: Chemical vs Physical Change
« Reply #5 on: September 10, 2006, 09:51:51 PM »
ii) grease spot is dissolved with cleaning fluid - chemical

I think this is just a physical change.  The grease does not react with cleaning fluid; it just becomes sequestered and disolved in detergent micelles.

Offline Borek

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Re: Chemical vs Physical Change
« Reply #6 on: September 11, 2006, 02:36:56 AM »
I think this is just a physical change.  The grease does not react with cleaning fluid; it just becomes sequestered and disolved in detergent micelles.

I second that.
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Offline P

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Re: Chemical vs Physical Change
« Reply #7 on: September 11, 2006, 09:08:02 AM »
I too would have said that this is a physical change as no 'chemistry' takes place.
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Offline jennielynn_1980

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Re: Chemical vs Physical Change
« Reply #8 on: September 11, 2006, 12:29:12 PM »
What about sugar dissolving in water.  Is that chemical or physical?  Does the lump of sugar break up into tiny sugar molecules or do the actual carbon and hydrogens bond with the water molecules?

Offline Yggdrasil

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Re: Chemical vs Physical Change
« Reply #9 on: September 11, 2006, 01:00:19 PM »
The lump of sugar disolves into single sugar molecules and no chemical bonds (i.e. covalent bonds) are broken.  Only intermolecular bonds (bonds between molecules like hydrogen bonds, dipole-dipole interactions, and van der Waals forces) are broken.

Offline Donaldson Tan

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Re: Chemical vs Physical Change
« Reply #10 on: September 11, 2006, 03:15:49 PM »
In dissolving sugar, the molecular integrity of sugar is maintained in the process.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline constant thinker

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Re: Chemical vs Physical Change
« Reply #11 on: September 11, 2006, 03:37:17 PM »
Now that Yggdrasil and Borek mention it...

Number 2 is a physical change. I didn't put much thought into, but Yggdrasil's explanation makes it out to be a physical change. Which I now agree with after thinking about it.

Geodome's comment seals the deal though. I now have to agree it's a physical change.
"The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' " -Ronald Reagan

"I'm for anything that gets you through the night, be it prayer, tranquilizers, or a bottle of Jack Daniels." -Frank Sinatra

Offline antoinetta

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Re: Chemical vs Physical Change
« Reply #12 on: September 11, 2006, 07:28:44 PM »
Hey, thanks for everyone's reply.  It certainly clarify things.
The oldest, shortest words - "yes" and "no" are those which require the most thoughts.  - Pythagoras

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