Question

What type of energy is released when a firecracker explodes

Answer 1

There is heat, light and sound energy, that is released. 

Answer 2

-- Sound energy.  That's how you hear it explode.

-- Light energy.  That's how you see it in the sky.

-- Heat energy.  That's why you get burned if sparks fall on you.

-- Potential energy, as all the pieces fall to the ground.

These were all stored in it as chemical energy before it exploded.