Answer:
A gasoline engine transforms approximately 34% of the fuel's chamical energy into mechanical energy.
Step-by-step explanation:
Many forms of combustion are examples of converting chemical energy into mechanical energy. Chemical energy is locked in the bonds of any combustible material: Gasoline, kerosene, wood, black powder.
Shooting off fireworks, igniting that bottle rocket converts the fuel inside into an exhaust gas which propels the rocket. Pulling the starter cord on your lawn mower ignites the fuel, releasing the energy that drives your lawn mower.
Automobiles, trains, planes all have combustion engines. Jet planes burn fuel more like a rocket engine, using the force generated by directed explosive gases.
The more interesting of this basic conversion principle today is in trying to create the stored chemical energy from mechanical energy. In other words, converting mechanical energy into clean fuel. One of the easiest to see is the use of wind power to produce the mechanical energy to create a DC energy and using that DC energy produce hydrogen from water via the process of electrolysis:
The wind drives the mechanical device that essential rotates a conductor through a magnetic field creating the DC voltage used to separate the hydrogen and oxygen. That mechanical to chemical conversion produces a pure hydrogen which has much more combustion potential energy than an equivalent mass of gasoline.