Question

Hi! Can someone tell me which formula for heat exchange is to be used? For some questions my teacher uses m1c1∆T=m2c2∆T and for some she uses m1c1∆T=-m2c2∆T, i'm reaaly confused and need help soon! I have a test tomorrow!

Answer 1

heat lost by one system = heat gained by another system

Answer 2

The idea is to make the math match the concept (which Yahoo! expressed perfectly). The problem is "should negative heat represent heat lost or heat gained" and for which system. Different people use different conventions - you'd have to ask you teacher. The rule that I teach is "start with a system or object and heat gained by that object is positive and any heat lost by that object is negative. If another object is gaining heat then it means the first object lost it, so that is a negative heat transfer."

Answer 3

thanks! :)