The density of a substance refers to its mass in relation to its volume. In the case of petrol and kerosene, petrol (gasoline) is generally less dense than kerosene. Here's a comparison of the densities of petrol and kerosene at standard temperature and pressure (STP):

1. Petrol: The density of petrol typically ranges from 0.72 to 0.77 grams per cubic centimeter (g/cm³).

2. Kerosene: The density of kerosene typically ranges from 0.78 to 0.81 g/cm³.

Based on these values, we can see that kerosene has a higher density than petrol. This means that for the same volume, kerosene will have a greater mass compared to petrol.

In summary, kerosene is denser than petrol, making it heavier per unit volume.