How do cars burn fossil fuels?

Answer 1

Burning fossil fuel takes free oxygen from the air. In a car, air, which includes free oxygen, comes into the engine through an air filter and the air is then mixed with fuel and sent to the engine. The fuel-air mixture is ignited, gets hot, its pressure rises and this drives down a piston that drives the crankshaft.

The fuel contains carbon and hydrogen, and the burning process unites carbon with oxygen, and also hydrogen with oxygen. Both these chemical process produce a lot of heat.

The formation of these chemical bonds generates CO2 and H2O, also known as carbon dioxide and water, which are the major products of burning fossil fuel. In round numbers, burning 1 kg of fuel takes 3.5 kg of oxyen from the air, and generates 3.1 kg of CO2 plus 1.4 kg of water; and about 50 MJ of heat energy is generated.

In the average car engine, about 25% of the heat energy produced is converted into mechanical energy to drive the car.