Iron (III) chloride catalyzes the decomposition of hydrogen peroxide because the decomposition of hydrogen peroxide is usually inhibited by the presence of ions such as phosphate ions in solution. The iron ions that would result from the dissolution of iron (III) chloride have a charge of 3+ and would bond with the -3 charged phosphate ions, creating a non-charged FePO4 molecule and removing the decomposition inhibitor from the solution. Potassium iodide and potassium chloride both are more strongly bonded than a transition metal compound and would lack the necessary charged iron ion when added to hydrogen peroxide.
An object has a negative charge if it's atoms have more electrons. On the other hand if an object had more protons, then it would have a positive charge.
The moon's shifting of position makes it "appear" as being smaller or bigger. This is simply because the moon is rotating and the sun's light shines on a certain area of the moon, and depending on where we are on the Earth is how the moon looks or appears to our perspective.
