Short answers, pulled from the story.
Hydrogen, helium, water, ammonia, methane, hydrogen sulfide, phosphine, halogens, noble gases, carbon monoxide, sulfur dioxide, hydrogen chloride, and hydrogen fluoride are the primary volatile substances. These materials vaporize easily compared to refractory substances like iron and silicon which remain solid under similar conditions.
Jupiter and Saturn contain vast amounts of hydrogen and helium making them gas giants while Uranus and Neptune hold higher melting point ices classifying them as ice giants. The distinction relies on whether substances exist primarily as gases or ices within the specific thermal environment of each planet.
Explosive events occur when trapped gases force their way through thick felsic rock with high viscosity that prevents easy escape. Low silica mafic magma allows volatiles to escape more easily during effusive eruptions releasing lava fountains or flowing streams instead.
Melting points above 100 K define substances as ices rather than gases according to standard planetary science classifications. This threshold determines how water ice sublimates to drive cometary activity outward into space inside Jupiter's orbit.
An empirical equation states n equals 0.1078 times pressure for water in certain magmas while rhyolite holds water at a rate of 0.4111 P. Basalt loses water faster than rhyolite as pressure decreases near the surface causing saturation levels to change rapidly.