1. THE SUN: Fusion, Fission and Combustion
Earth & Environmental Science
THE SUN: Fusion, Fission and Combustion

2. Definitions Fusion- Combining of nuclei
Fission- Splitting of a nucleus
Combustion- Chemical reaction in which an atom combines with oxygen

3. What is the Fuel? Fusion Fission Combustion
Uses small, light atoms like Hydrogen
Fission
Uses large, heavy atoms like Uranium
Combustion
Uses any substance that will react with Oxygen

4. How Does it Start? Fusion Fission Combustion
Requires great heat and pressure
Fission
Starts when a neutron strikes the nucleus and causes it to split. More neutrons are released causing a chain reaction.
Combustion
Requires small amount of energy to activate the reaction.

5. What is Released and/or Converted?
Fusion
Releases large amounts of energy. Mass is converted to energy.
Fission
Combustion
Releases smaller amounts of energy that are present in the bonds between atoms. Reactants start at a higher energy level than products.

6. How Long does the Reaction Last?
Fusion
Does not explode because there is no chain reaction
Fission
Can explode because of chain reaction
Combustion
Once started, heat from combustion will keep the reaction going as long as the reactants are present.

7. Where does it Happen? Fusion Fission Combustion
Happens in core of a star. Can happen briefly in a laboratory. Happens in a hydrogen bomb.
Fission
Happens in nuclear power plants. Happens in an atomic bomb.
Combustion
Happens any time there is a fire. Can also happen slowly as in the case of something rusting.