In tomorrow's lecture I will talk about immiscible liquids. This shows the importance of entropy of mixing. The temperature-composition phase diagram of two partially immiscible liquids has a critical point. There is a nice video of the critical opalescence associated with the critical point for the cyclohexane-methanol mixture. An Excel spreadsheet for the thermodynamic data is here.
The simple analytical formula for mixing of a regular solution shows how the competition between energy and entropy which drives phase transitions.