I think the answer you're looking for is digestion.
The two molecules will only react if they have enough energy. By heating the mixture, you are raising the energy levels of the molecules involved in the reaction. Increasing temperature also means the molecules are moving around faster and will therefore "bump" into each other more often.
Roughness of the surface and weight of the object.
Answer:
Lithium has 5 elements, sulphur has 2 elements and oxygen has 4 elements
