A conversion factor is a fraction that is always equal to the value of 1.
Think of it this way: it is a distribution problem in which you are multiplying the 2 on the outside with each element in the parentheses. Oxygen does not have a number in front of it, so put an imaginary one in front of it to help you. Do the same with Hydrogen since it doesn't have a number in front of it either. Now you know that hydrogen has one ion and oxygen has one... but you must now multiply each of the elements' ions by two. You should now know that Oxygen has 2 ions in Calcium Hydroxide and that there are also 2 ions of Hydrogen in Calcium Hydroxide. Does this make sense?
A wave is a disturbance that carries energy from one place to another. Matter is NOT carried with the wave! A wave can move through matter (a medium). If it must have a medium, it is called a mechanical wave.
The Molar mass of an atom corresponds directly with its atomic mass on the periodic table.