## open system

$\Delta U=q+w$

J_Rodriguez_Dis2k
Posts: 25
Joined: Fri Sep 25, 2015 3:00 am

### open system

Can anyone please explain to me why how an open system can still be used to calculate a change in volume ?

Milan M
Posts: 10
Joined: Tue Nov 10, 2015 3:00 am

### Re: open system

Not sure I 100% understand, but from what I have is: an open system is like a cup whereas a closed system is like a bottle. With bottles, we can't really get in there and add liquids or gas. With an open system like a graduated cylinder there can be both a transfer of mass and energy, since we can easily add/remove things from the system and compare the changes to a set point. Hopefully that answers your question for the most part.

Navi Sidhu 1F
Posts: 25
Joined: Wed Sep 21, 2016 2:59 pm

### Re: open system

I like to think of these problems like they have a moveable piston; one that moves up or down while responding to volume changes inside the beaker/cylinder in order to make the internal and external pressure equal, as it is in a open system.

For example, Gas A (3 L) and Gas B (2 L) react to form 6 Liters of Gas C. Since there was a creation of 1 L of Gas, work was done by the system.

Here's a diagram that explains what I'm saying: