Question

why is the equation of first law of thermodynamics diff in chem and phy .

Answer 1

only the signs are diff .in phy it is work done by the system and in chem it is work done on system

Answer 2

You've just said it:
(English) physics text books and chemistry books use different conventions for signs of work.

There is no such change of convention in French or German textbooks:
http://fr.wikipedia.org/wiki/Premier_principe_de_la_thermodynamique

Answer 3

It doesnt matter....in physics and chemistry and even in biology 1st law of thermodynamics is same. the difference is the system that ur working with. in physics its a physical system and in chemistry its chemical system. If u r in detail, then u can find all r same

Answer 4

no ther is nothing like different conventions
in phy work since it is work done by sym is denoted as -w
in chem work since it is work done on sym is denoted as +w

Answer 5

in physics workdone on system is +w
in chemistry workdone by system is -w

Answer 6

"in phy work since it is work done by sym is denoted as -w
in chem work since it is work done on sym is denoted as +w"

Well choosing if you take into account work done BY or ON the system to write a formula, is what you call a convention, don't you?

Answer 7

-w means u hve to supply energy to do that work lack of energy
+w stands for excess energy of the system which converted into work