The gravitational pull generates this cool thing called tidal force, which kinda pushes the water to the side closest to the moon. When the tide is high, that means the moons closer to that point than somewhere else.
Two sides will always have high tide and two sides will always have low tide.
The 3 indicates the third electron shell. (Which has only 1 electron in it in this configuration)
Hope this helps! :)
The liquid will stop converting into vapor. This process is to balanced the amount of substance of both phases inside the flask.
