The simplest U - tube manometer is a flexible straw (flexed so bottom looks like U ) filled with a little water. The gas pressure is from you blowing in air or sucking on straw.
1. Each group, get a flexible straw and plastic cup.
2. Fill cup with water.
3. Put flexible end of straw into water and then suck up the water.
4. While still sucking up the water, place finger on the end of straw that is under water. Then flex the straw to make the U tube. You must do this under the water level for it to work.
5. Make observation of the liquid level on each side of the tube once they equalize out.
6. While one partner sucks up on the straw/liquid, the other observes the water level change. Make observations
7. Repeat except for gently blowing into straw.Make observations