The joule (J) is a unit of energy. Recall that energy may be converted between many different forms such as mechanical energy, thermal energy (heat), chemical energy, electrical energy, and light.The mechanical energy produced by a system is called work. When work is accomplished through the changing volume of a gas, it is called PV work and is given by the formula w=−PΔV, where w is the work, P is the external pressure, and ΔV is the change in volume. If the volume change and pressure are in liters and atmospheres respectively, then the work will have units of liter-atmospheres, which can be converted to joules using the conversion factor 1 L⋅atm=101.3 J.Work can also be expressed as force multiplied by distance: w=F×d, where w is the work in joules, F is the force in newtons, and d is the distance in meters. Note that 1 N⋅m=1 J.