Can someone please solve this question i do not get it

Nuclear fusion is the source of energy for stars. besides hydrogen, which other element is most likely also common in stars?

Using a value of ksp = 1.8 x 10-2 for the reaction pbcl2 pb+2(aq) + 2cl -(aq). if the value of ksp was determined to be only 1.2 x 10-2: too much solid has dissolved. additional precipitate is forming. the solution is unsaturated. the ions are now combining to reduce their concentrations.

What are the similarities of physical and chemical change ?