THESE ARE MATCHING, NOT SURE WHICH ARE RIGHT OR WRONG SOME ANSWERS MAY NOT BE SHOWN the energy required to initiate a reaction

the slope of the concentration profile at a specific position

mass transport by atomic motion

akin to 'conductivity', indicative of the rate of atomic diffusion

time rate of atoms or mass passing through a unit area

diffusion flux is proportional to the concentration gradient

time rate of change of concentration is proportional to the $2$ nd derivative of the concentration

diffusion of atoms of one metal into another metal

atoms move from one interstitial site to another

interstitial site

a rate or process that is dependent on time