# Use Einstein’s mass–energy equivalence relationship ?=??2 to calculate the energy released by processes in which mass is converted to energy

The Energy released when mass is converted to energy, is given by the equation: E = mc2

– production of energy by the sun

• Energy production in the sun happens through nuclear fusion
• The light atoms such as hydrogen get fused to form a heavier atom.
• The difference in mass between the initial atoms and final product gets converted to energy according to the equation E = mc2

– particle–antiparticle interactions, eg positron–electron annihilation

• When particles interact with their antiparticles, they get annihilated.
• This results in the complete conversion of mass of the original particles to some form of energy.
• Eg – electrons and positrons get annihilated to form photons.
• e + e+ -> y + y
• e : electron
• e+ : positron
• y : photon

– combustion of conventional fuel

• combustion of conventional fuels mostly release energy due to chemical changes
• For example, burning about 3kg of gasoline releases about 132 million joules of energy,
• This energy if converted to mass will be 14 ng of mass.
• Thus by losing only 14ng of mass (a negligible amount), it is able to produce 132 million joules of energy.

Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)