The exothermic explosive is a high tech explosive that concentrates the heat from the sun drawing a beam of energy down and building up pressure hot enough to burn a large area around it. Upon detonation, it will start absorbing heat from the sun and it's pressure will inhale nearby blocks towards the center tossing them around the beam until enough heat builds up.
It will then expand and toss all the blocks in the air outwards following with a blast of immense fire and lava across the land. The exothermic explosive has a 1% chance of producing lava and a 30% chance of burning a block below a lighted fire into netherrack lighting up the area forever.
The exothermic explosive however is expensive and only works in afternoon as it requires the concentrated heat from the sun. Any other time in the day or at night the exothermic explosive will simply not work. The explosive will also not work when it rains or if there is a block obstructing it's view from the sun.
Missile form of the above Explosive