A decomposition reaction turns molecules into smaller molecules (or even atoms). Examples of decomposition reactions are electrolyses, photolysis, thermolysis (and many more). Whereas a combustion...
A chemical reaction changes the actual chemical make-up of a molecule while a physical reaction only changed the physical state of a molecule, the atomic make-up in the molecule stays the same. (ex:...
An involuntary reaction is one that you can't control, like a sneeze. A voluntary reaction maybe the decision to stand-up, take a walk, do push-ups, or turn pages of a book