Hi, I learned recently Avogadro's principle which states " At constant temperature and pressure, equal volumes will contain the same number of molecules" this can be translated to if you double the volume, you double the number of moles. Now i don't get that at all!! where does the extra particles come from as you double the volume? can't doubling the volume still hold one mole but spread out at greater area? the other problem i have is conceptual: In thermodynamics practice i was asked: if volume is increased and pressure remains constant, what happens to temperature? My answer ws it decreases and the reasoning behind this was: as volume is spread out, average kinetic energy will spread over a larger area and temperature will decrease. I was wrong, the answer was: Temperature increase as stated by PV=nRT. why is my reasoning incorrect?