Galactic is referring to the galaxy and cosmos! :)
The answer is the last one .... The ability to do work and cause change
Mg gained mass because it went from being a single element (on the reactant side) to being a molecule (on the product side).
The usual units of density are g/cm.
You may have also seen g/mL used for density. Keep in mind that 1 cm = 1 mL.
Anions are negative ions so it’s when an atom gains electrons
