A jar filled partially with water has an object floating in it. The jar is open. Now, if the jar is closed and a vacuum pump is used to pump the air out, what will happen to the floating object? will it rise up more or sink or ...? and why?
You cannot remove the excess air above the liquid and leave the liquid behind. As the pressure above the liquid decreases, the evaporation rate of the liquid will increase and more and more will turn to a gas. Ultimately as the pressure is decreased the liquid is in effect "boiling" at room temperature. Until all the water has been turned to a vapor and removed by the pump you cannot significantly lower the pressure in the container. If the pump runs long enough, the object will be sitting on the bottom of an empty container.