[Lx]

I could definitely be wrong but when I took chemistry and physics a long looong time ago. We diagrammed chemical equations and everything balanced out except for a catalyst which comes through unscathed.

In physics, I'm pretty sure the teacher said that it was only a dime's worth of mass that was converted to energy in either Hiroshima or Nagasaki (the yields were reasonably close).
If I have a bowling ball at the top of a hill, it's potential energy, if I let it roll it's kinetic energy, does the bowling ball gain mass?
When it stops, does it then lose its gained mass?

Needless to say, I'm not a nuclear or chemical engineer nor a physicist and I didn't stay at a Holiday Inn last night although I did stay at a fleebag hotel next to Burbank's airport, does that count as anything?

[spunkets]

"If I have a bowling ball at the top of a hill, it's potential energy, if I let it roll it's kinetic energy, does the bowling ball gain mass? When it stops, does it then lose its gained mass?

Yes, to both questions. As with your ordinary chem though, the E and m change is too small to be significant.

The total mass is given by,

m = m₀/sqrt(1-v²/c²)

m₀ is the rest mass. You can see that if v is small the changes don't mean much.