This explains the soda straw phenomenon. When you suck liquid up a straw, all you re doing is creating a vacuum at the top of the straw. The atmosphere then pushes the liquid into your mouth. Water also has a straw too long whose length you calculate in the prelab. The weight of the atmosphere that pushes soda up straws is usually given in units of pressure, not weight.
Weight is a force, and pressure is force per unit area.
The definition of pressure as force per unit area is extremely important in understanding pressure. Consider the 76 cm high column of mercury we balanced on your head earlier. We said the column doubles the weight, or force, on your head at that spot. To double the force on your whole head, we d have to cover your entire head with a column of mercury 76 cm tall at every point. If we did that, we d increase the pressure on your entire head.