Question

what causes a reaction to be spontaneous? provide an example for your explanation

Answer 1

Spontaneous reaction happens in nature and usually it produces
Energy in form of heat, light or electricity.

E.g burning of methane is spontaneous, heat is released.
Spontaneous reaction needs an activation energy, like
Firing the methane needs a spark.

Reaction

CH4 + 2 O2 -> CO2 + 2 H2O

When reactants are converted to products, new
Bonds are formed and these bonds contain less
Energy as original bonds.

When reaction is going on, it produces enough energy.

Answer 2

Thank you @Gebooors