Re: How do u differente between physical and chemical properties PLEASE READ!!!

Hi Kim,

You're on the right track.  Water solubility is a physical property, even 
though sometimes water solubility involves bond breaking (bond breaking is 
part of the definition of a chemical property).  I find this to be 
confusing, and am assuming you just need to memorize some of the 
accepted property classifications that aren't intuitively obvious.  
According to the same logic, the pH of a solution is also a physical 
property despite that pH sometimes involves bond breaking in order to 
increase H+ in solution.  I am still not sure about these two: neutral to 
litmus paper, pH 6.9 in 1% solution.
    
This is what I'd suggest:

Physical properties...
Qualitative
  white, odorless powder
  long, needle-like crystals
  bitter taste
Quantitative
  MW 194.19 g/mole
  m.p. 238 C
  sublimation point 178 C at 1 atm
  water soluble

Chemical properties
  generally non-reactive
  *crystals of monohydrate precipitate from solution upon cooling 
     (while crystallization might not result in new chemicals, bonds must       
      be created to form the crystal lattice) 
  *crystals lose water of hydration slowly to give white solid 
     (since water is complexed with the caffeine, bonds must be broken in             
      order for the water to leave the complex)

There's a nice website regarding chemical and physical properties in 
general at this address:  http://www.s
cidiv.bcc.ctc.edu/wv/0001-01-Chemistry.html
The chemistry texts I looked at did not give very clear explanations of 
physical versus chemical properties.  If I were you, I would ask a 
chemistry teacher at your school about this if you're still uncertain. 

Sarah Earley
CU Boulder