Why does the gas pressure decreases as the volume increases?

The gas pressure decreases when the volume increases because when pressure builds up it gives more volume to the object. when there's less pressure there's less volume.

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .

Cause its being chemically applied?