Achemical reaction is most likely to occur spontaneously if the

- For a spontaneously reaction to takes place, the system must has a negative free-energy change ΔG.
- Because changes in all (free energy - entropy and enthalpy) are related to each other by the following equation :
ΔG = ΔH-TΔS,
So ΔG becomes more negative when entropy (randomness) increases, i.e.  when the products of a reaction are more disordered and less complex than the reactants.

Crust,mantle,core,earth

Heat is involved in chemical change in two ways; chemical changes either result in heat being added to or removed from an object, and chemical changes require a certain amount of heat before they can take place.