Disclosure: I am studying biochemistry so my thermodynamics education is lacking and I'm likely misinterpreting some of these concepts (that's why I'm here for help). I have always had trouble defining some properties as either intensive or extensive. I understand that extensive are supposed to depend on the amount of the substance present, but intensive properties do not. For example I can easily understand why boiling point is intensive and mass is extensive. However I get confused when I try to place some properties into either category. One that always gets me is pressure. I have heard the argument that if I have sealed a box with a pressure of 1atm inside and I split the box in two I have reduced the number gas molecules as well as the volume by half and the pressure doesn't change. So pressure is not dependent on amount.... Ok, that makes sense to me, but what if I doubled the amount of gas in the box (increases the amount of substance) Hasn't the pressure gone up? Im sure there is some fundamental flaw in my reasoning and I'm hoping that when this is cleared up I will have a much more sound understanding of intensive and extensive properties (or pressure for that matter). Thanks in advanced!