Later I heard that the price of an eye exam at target optical may vary from $29 to $229. So I think this may be the reason that why I can't find the price on the internet. if you want to have an eye exam at target optical, I strongly suggest you to make a call to know the exact price for en eye exam in that store.
Water does not commonly form a gas, but rather a vapor which is slightly different (but really just the name of a gas that is normally a liquid). - There is latent heat in water so you can remove energy without changing the temperature of the water (only exactly at a phase change though).
Yes, but it depends. Boiling point represents a phase change of matter. Water molecules will require sufficient energy (kinetic energy) to escape the liquid phase and accelerate into the vapor phase. More water simply means more energy is required to bring about the phase change, however the boiling point temperature will remain fixed. In other words, the amount of energy required to undergo phase change for every individual H2O molecule is always the same, but more molecules means more energy input is required.