Ok, ppl these r my doubts when is studies pressure, barometer. For each points i will need explanation. In fact, i really need them to help me understand, so i will really appreciate your effort. 1.will there be changes made to the length of mercury column when there is an addition of mercury? 2.will there be changes made to the length of mercury column when mercury is being evaporated from the mercury reservoir? 3.will there be changes made to the length of mercury column when the mercury column is being pushed further down into the mercury reservoir? 4.will there be any changes when the liquid in the barometer changed to eg, water? 5.what will be the change in length of the mercury column when the barometer is brought to a place of low altitude? 6. will will happen if there is air in the space on top of the mercury column?( which usually suppose to be vacumn) and why? how to determine atmospheric pressure like that?