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How does expanding burned gas move a piston in a gasoline engine?

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Labeled cross-sectional diagram of a V-type gasoline engine for an automobile, showing internal components such as pistons, crankshaft, camshaft, intake and exhaust valves, connecting rods, spark plugs, and intake manifold. — gasoline engine Cross section of a V-type engine.

In a gasoline engine, the movement of the piston during the power stroke is driven by the rapid expansion of gases resulting from combustion.

Following the compression stroke, the air-fuel mixture is ignited by an electric spark while both the intake and exhaust valves remain closed. This ignition triggers a chemical reaction that releases heat and creates high-pressure gaseous products within the cylinder. Because the combustion chamber is sealed at this stage, the expanding burned gas exerts significant force directly against the piston head (or crown).123

This pressure pushes the piston downward, converting the thermal energy of the expanding gases into mechanical work. The piston is connected to a crankshaft via a connecting rod, forming a slider-crank mechanism that translates this linear, reciprocating motion into the rotary motion required to power the vehicle.345