why is sulfur insoluble in H2O? what factors affect this observation?

Answer 1

For any substance to dissolve in water, it need to be polar. Polar substances have one area of the molecule more electronegative than the other section. Electron distribution is greater in this region.
Sulfur, being an element, is atomic; it is comprised of single atoms of sulfur. Since atoms have an even distribution of electrons (there are no area of an atom that has higher electronegativity), it is non-polar. Therefor, it does not dissolve in water.