We introduce thermodynamics with the First Law, where internal energy change equals heat added and work done. State variables like pressure, volume, and temperature define a system's thermodynamic sta...We introduce thermodynamics with the First Law, where internal energy change equals heat added and work done. State variables like pressure, volume, and temperature define a system's thermodynamic state, independent of process paths. PV diagrams graphically represent processes, showing work as area under curves. In cycles, state variables return to initial values, making net internal energy change zero. Thermodynamic cycles help visualize energy transfers in processes involving gases and fluids.