The Experimental Error blog considers the difference between disciplines (via Tom):
I often contemplate the differences between these two areas of study. Also, I hear fellow undergrads argue for one or the other, usually divided along the lines of their respective major. Anymore, I think they're so interrelated that I find it hard to find a difference between the two, except for the phases of matter that they most often deal with.
Back in the days when science was new, Physics dealt with understanding the fundamental laws of the universe, and it was Chemistry that was making the attempt at understanding the fundamental pieces that the universe was composed of. Both of these fields also grew out of a long standing philosophical tradition that can be traced back to the days of the pre-Socratics, and exemplified by Aristotle. Buuuut... that's going a bit further back than I think is necessary to understand what's different, anymore, about these two sciences, if indeed they ever really were different.
He goes on through a nice discussion of the history of the two fields, and the similarities and differences between their approaches to the world. It gets complicated, and it's hard to draw the line.
My own view, as someone with a degree in Chemical Physics (which gives me just enough experience to appreciate the joke attributed to Art Schawlow: "A diatomic molecule is a molecule with one atom too many."), is that you can divide the different sub-fields based on their usual level of approximation. That has its messy points as well, but it works for me.
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To freshmen, the big difference between physics and chemistry is that chemistry professors harp on significant figures while physics professors harp on units and not plugging numbers into equations until the final step.
Does it matter?
If you want an aspirin you get a physicist. If you need an aspirin you get a chemist. If you want nobody else to have an aspirin you get a lawyer.
You're right in that it's hard to draw the line.
Does there need to be one?
Most chemists I know can quite happily perform most of the tasks that physicists do, and I'm sure the reverse is true.
About the only thing that gives me the expletives is when I say I'm a chemist and people ask me which chemists' shop I work in.
No, dear. That's a pharmacist.
As one who just finished the first general chemistry course alongside the first two general physics courses, I'm inclined to agree with Alex...sig figs and precision were a lot more important in chemistry, and deriving equations and understanding complex systems were more focused on in physics, at least at the introductory level.
Not only that, but it wasn't all that long ago when physics and mathematics were effectively the same discipline as well. Gauss would have considered himself a practitioner of both.
Glad you picked up on that article for comment. I liked it too, and might blog on it also.
Elijah, I am sure that the reverse is not true. You do not want physicists diluting HCl. I have to get special dispensation to do chemistry experiments in my physical science class. Maybe they heard about the time I set fire to the chem lab in middle school? Nah, no chance. Never had to call the fire department.
And the other way around? I hung out with at lot of experimental nuclear chemists in grad school, and they did not know nearly as much physics (including quantum mechanics) as physics grad students working in a related area.
And although I agree with the point about significant figures in chemistry, I find that students who pass chemistry still don't (or never did) get the memo about not rounding intermediate results and they have difficulty realizing that a physics lab operates on the same principles.
AMO physics has gotten a lot more "molecular" in the past 10 years, although their molecules are distinctly weird from a chemist's point of view - physicists tend to like molecules that would be marked wrong on a freshman chemistry exam. I (physical chemist) occasionally serve as the out-of-department reader for AMO physics PhD. students. I'll never forget the first time I saw a potential energy curve for which the energy scale was marked in kilohertz.
Chem has that whole history of alchemy thing going on. Physics springs much more out of people who liked engineering problems along with other interests. There's a lot of overlap, but historically they are pretty distinct, since well before the era of Newton futzing around trying to figure out the transmutation (supposedly as an effort to get closer to God through mysticism, according to an argument I read recently).
Also, quantum. That's straight out of voodoo, not alchemy :-)
be simple yaar
Both are equal, but according to my personal opinion physics provides more scope than chemistry
physics is concerned with the structure & behavior of individual atoms and their components, while chemistry deals with the properties and reactions of molecules.
WOOOOOW NERDS!!!!!!!!!
bean, without "nerds" you wouldn't have internet and computer to watch your porn.
I agree with leidy.
Physics is study of properties and behavior of an object as a whole.
Chemistry is the study of its component parts and how these react with component parts of other substances.
Ever heard "she" has good chemistry?