Electron-Positron Annihilation, In this reaction, a particle and antiparticle (an electron and a positron) collide, resulting in the formation of two gamma quanta. All the rest energy of the pair is converted into photon energy, Helium Fusion Reaction, Protons and electrons interact to form a helium atom. The mass difference is converted into kinetic energy and the energy of electron neutrinos:, Uranium-235 Nuclear Fission, -When colliding with a slow neutron, the uranium-235 nucleus splits into two fragments (e.g., krypton-93 and barium-140), emitting two or three neutrons and releasing a significant amount of energy, Methane Combustion, Methane reacts with oxygen to form carbon dioxide and water. This is an exothermic reaction, often used as a fuel, Each of these reactions illustrates fundamental processes of matter and energy transformation in nature.