Thermodynamics is a branch of chemistry and physics that deals with energy. The basic function of the engine is to convert chemical energy (stored in the atomic bonds of the gasoline) to rotational kinetic energy (rotating shaft). There is at least one intermediate step and other form(s) of energy involved. What are they? Trace the flow of energy (identify each step where energy is converted or transferred) through the engine from the gas tank to the output shaft. Is any of it wasted? How? (e.g. Is the engine 100% efficient at converting the fuel into mechanical power?)

Background A spark-ignition gasoline engine converts the thermal energy released by the combustion of gasoline, to the mechanical energy of a rotating shaft using a thermodynamic cycle known as the Otto Cycle. The Otto Cycle is best visualized by looking at a graph of the Pressure versus the Volume of gas in the cylinder as the piston moves through the cycle as shown in Figure A below. Pressure in the Cylinder End of combustion P P Ignition Intake valve opens *TDC Expansion Compression Exhaust Exhaust valve opens Intake valve closes "BDC Air-fuel mixture Intake Volume of the cylinder Figure A: P-V Diagram of the Otto Cycle with diagrams of the four strokes of the cycle V Power (expansion) stroke Exhaust gases Compression stroke (a) Actual four-stroke spark-ignition engine Air-fuel mixture Exhaust stroke Intake stroke TDC = Top Dead Center. This occurs when the piston is positioned at the highest point in the cylinder (the volume of the cylinder is the smallest). BDC = Bottom Dead Center. This occurs when the piston is positioned at the lowest point in the cylinder (the volume of the cylinder is the largest).