* Homogeneous mixture: A mixture where the components are evenly distributed throughout, meaning it has a uniform composition.

* Heterogeneous mixture: A mixture where the components are not evenly distributed, and different parts of the mixture have different compositions.

Petrol is made up of a complex blend of different hydrocarbons, but these are all dissolved in each other, forming a single, uniform liquid. You can't see individual components or layers within petrol.