Write the equation that expresses the first law of thermodynamics in terms of heat and work?

is the algebraic equation delta E = q+ w

delta E is change in internal energy, q is heat, w is work

just asking if this is right

i'm a bit confused cause wikipedia says

delta E= q-w

but then it says

When the system evolves in a non adiabatic way, it is observed that the work exerted on the system does not coincide with the increase in its internal energy, which, being a state function, can be used for both adiabatic and non-adiabatic processes.

w does not equal delta E (change in internal energy)

w+q = delta E


4 Answers

  • You are confuse with sign convention and nothing else.Most widely accepted sign convention are Heat given TO the system and work done BY the system is taken as positive while Work done ON the system and heat given BY the system is taken as negative.So by following that convention we get

    delta e = q - w

  • Heat Work Equation

  • You have those variables out of order...the correct version is:

    Q = deltaE + W

    Here is the motivation of your sign convention, which I recommend you use:


  • According to mastering chemistry, those are work.

    The answer is E=q+w

    Source(s): Mastering Chemistry

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