[RuiRui322]

I have a question about the gas collection over water lab:

We learned that when the water level inside the graduated cylinder is higher than the outside water level, the gases inside the graduated cylinder have a lower pressure than atmospheric pressure.

Then by adjusting water level of the graduated cylinder to match the water level outside would equalize pressure. However Shouldn´t the volume of the gas decrease if the pressure is increased? SHouldn't the water level go up as you push the cylinder down beneath water level or go down as you lift it through the water? Does Boyle´s law (PV = PV) not apply here? Why?

[mjc123]

SHouldn't the water level go up as you push the cylinder down beneath water level

It should go up relative to the cylinder (so the volume of gas decreases with increasing pressure), down relative to the water level outside the cylinder (but not as far down as the cylinder moves).