Petrol, also known as gasoline, is a mixture of hydrocarbons, primarily alkanes with 4 to 12 carbon atoms per molecule.

Here's why hydrocarbons are flammable:

* Carbon-Hydrogen Bonds: Hydrocarbons are made up of carbon and hydrogen atoms bonded together. These bonds store a significant amount of energy.

* Combustion: When hydrocarbons react with oxygen (in the presence of a spark or heat), the bonds break, releasing the stored energy as heat and light. This process is called combustion, and it produces a flame.

The specific chemical composition of petrol can vary depending on the source and refining process, but it's always primarily made up of hydrocarbons, making it highly flammable.