Briefly explain the difference between self-diffusion and inter-diffusion. (a) Compare interstitial and vacancy atomic mechanisms for diffusion.
(b) Cite two main reasons why interstitial diffusion is normally more rapid than vacancy diffusion.

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.

The answer will be c