Use weights or books on top of the syringe scale to measure pressure with this additional weight. You've seen Boyle's Law in action when you've shaken a can of pop. As you open it the liquid ends on you and your surroundings. Let the can cool.
Air pressure is a force that acts on the outside surface.
First boil a small amount of water in the flask and immerse the flask into the beaker of cold water. The water level in the flask increases. When an additional amount of hot water is poured over the flask, it will cause the water level inside to decrease. Cover the mouth of a small flask with a rubber balloon and gently heat the flask. The balloon will inflate.