When a hydrocarbon burns, it reacts with oxygen in the air. This reaction produces carbon dioxide (CO2), water (H2O), and energy (in the form of heat and light).

Here's a simplified chemical equation for the combustion of methane, a simple hydrocarbon:

CH4 + 2O2 → CO2 + 2H2O + energy

In summary, the elements present in the products of hydrocarbon combustion are:

* Carbon (C)

* Hydrogen (H)

* Oxygen (O)

The oxygen comes from the air, while the carbon and hydrogen come from the hydrocarbon itself.