How does gas make an engine run?

In an internal combustion engine, such as those found in most cars, gas (usually a mixture of hydrocarbons such as petrol or diesel) is used to create the energy needed to move the vehicle. Here's a simplified explanation of how gas makes an engine run:

1. Intake Stroke: The engine's intake valve opens, allowing a mixture of air and fuel (gas) to enter the cylinder.

2. Compression Stroke: The piston moves up inside the cylinder, compressing the air-fuel mixture to increase its pressure and temperature.

3. Power Stroke: At the top of the compression stroke, the spark plug ignites the compressed air-fuel mixture, causing a controlled explosion. This rapid expansion of hot gases creates pressure that forces the piston back down the cylinder. This is the power stroke, which moves the crankshaft and flywheel, the main rotating components of the engine.

4. Exhaust Stroke: As the piston moves down during the power stroke, the exhaust valve opens. This allows the burnt gases from the combustion to be pushed out of the cylinder and eventually expelled through the exhaust system.

These four strokes occur repeatedly in a four-stroke engine and, through a series of gear reductions, convert the reciprocating (up-and-down) motion of the pistons into rotating motion that drives the wheels of the vehicle.

Overall, it is the controlled burning of gas that creates the high-pressure gases that drive the pistons and generate the movement required to power the engine.