The oxidation half reaction of the reaction given above would be: Ca → Ca + 2e−. Oxidation is the loss of electrons of an element while its counterpart is called the reduction which gains the electrons that has been lost. Hope this answers the question.
Diffusion of one state of matter into another: Solid can diffuse in liquid. When sugar is added to water, whole water becomes sweet without stirring it because of diffusion of sugar into water. ... Carbon dioxide and oxygen are the two gases in air which dissolves in water by diffusion.