The process in which a heavy nucleus splits into two lighter nuclei with the release of enormous energy is called: MCQ with Answer and Explanation

Explanation:
Electrolysis of water splits it into hydrogen and oxygen, it is not a purification method but a decomposition. Reverse osmosis uses semipermeable membrane to remove ions and impurities. UV irradiation kills microorganisms. Distillation boils water and condenses steam, removing non-volatile impurities. Other methods: filtration, chlorination, ozonation, boiling.

Explanation:
Pencil 'lead' is a mixture of graphite and clay. Graphite's layered structure allows it to leave marks on paper. Diamond is too hard and would tear paper. Fullerene is a nanomaterial, not for writing. Charcoal is used for drawing but not pencils.

Explanation:
Salt is obtained by evaporation of seawater in shallow ponds. Water evaporates leaving salt behind. Filtration cannot separate dissolved salt. Distillation would give pure water, not salt. Sublimation for sublimable solids.