text: Depends on what you want to measure:\n*Pressure: a manometer is most commonly used to measure the pressure of gasses of a given temperature and quantity.  A manometer works by displacing mercury from a glass tube (measure mmHg - "millimeters mercury"). \n*Volume: a simple way is to measure volume by displacement (i.e. a balloon of oxygen placed into a bucket of water - measuring the water that is displaced)\n*Weight: weight it.  Or you can go the hard way, multiply the volume of water by the molarity of water (I think it's 1.00M), and the answer by the molecular weight of water (in amu, from the periodic table).\n*Temperature: thermometers, perhaps...