Now, in this particular case, we have this artificial barrier, or door, if you will, that essentially prevents the molecules from this side going into this side. So all the six molecules and each molecule carries a certain amount of energy are essentially localized or concentrated on the left side of our container. Now, as soon as we open that door, what exactly happens? Well, before we open the door, what can we say about the energy in our system? So how much energy is found on this side and how much energy is found on this side? Well, notice that we have six molecules on this side, and each one of these molecules carries a certain amount of energy.