Which factor is needed to begin a nuclear fission reaction?
high temperature
stable nuclei
addition of a neutron
low pressure

addition of a neutron

Explanation:

Nuclear fission is a radioactive decay process in which a heavy nucleus spontaneously disintegrates into lighter ones accompanied by the release of energy.

An atom whose neutron/proton ratio is the same as that of the stability ratio of that atom is said to be stable. When such an atom is bombarded with a neutron particle, the stability ratio is offset. What results is a radioactive decay of such a nucleus. This form of decay is a nuclear fission.

A series of chain reaction is produced though this until the stability ratio is reached.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.