What type of energy conversion occurs at the moment fireworks explode?

chemical energy converts  into light, heat and sound  energy

Rapid Oxidation

Explanation:

In fireworks, the energy source is the rapid oxidation (burning or exploding) of gunpowder and other flammable chemicals. This burning causes the formation of gases that are heated and expand.

This rapid expansion involves three forms of energy : 1) The motive force to carry aerial fireworks into the sky, and to separate parts of them, 2) The heated molecules that give off radiance (visible light) in various forms of displays, and 3) The energetic vibration of air molecules that creates the sound of explosions.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it