I was not really certain what you were implying with making bombs with fire elemental magic, hence the specification (there was an incident with a player thinking that since their character can control fire, they can also create violent basketball-sized explosions *inside* other played characters standing some ways from their character with but a thought).
 - From what I've derived from the description of elemental magic, it wouldn't be possible to permanently alter the qualities of something with it, though ... just heat and burn things. Fire elemental affinity can strengthen other fire-related spells, but he'd still need to know some rather specific and probably complex (most likely arcane) spells to aid alchemical processes with magic.