The first law of thermodynamics can be expressed mathematically as:

Explanation

First law of thermodynamics states " energy can neither be created nor destroyed, it can only be altered/changed into different forms". Δθ= Δu + Δw is one of the mathematical expression for first law of thermodynamics which explains that heat supplied to the system(Δθ) is equal to change in internal energy of the system(Δu) plus work done by the system on the surrounding(Δw).