Phase Diagrams Concept 2

by Jules Bruno
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we're not going to take a look at the phase changes associated with the typical phase diagram. Now recall that a phase change is a reversible change. It involves a transition between the three states of matter, solids, liquids and gasses, we're gonna say associated with this phase change is what we call a phase change curve. This is just our line segment within phase diagrams that separates three states of matter. Uh Two states of matters to states of matter from each other. So if we take a look here at this typical phase diagram, we have our solids or liquids and gasses were going to say here that in this blue line, we're separating the solid phase from the liquid phase. Now, if you think about it, what do we call going from a solid to a liquid? We call that melting and in chemistry of fancier term forward is fusion. So we're gonna say here that this is our melting or we call our fusion curve For the Green one. Were separated separating the solid phase from the gaseous phase. If we think about it, what do we call gorn from a solid to a gas. So we've talked about this several chapters ago, going from a solid to a gas is called sublimation. So this green line will be our sublimation curve. And then finally we have our liquid and our gas faces being separated by this red line. Thinking about going from a liquid to a gas that's vaporization. So this is our vaporization curved. Now with this whole idea of phase changes. We have involved are normal pressure. So normal pressure is 762 or or 760 of mercury or just one atmosphere. We're going to stay here. That no pressure Is the name given to the standard pressure of one atmosphere or 760 of Mercury or tour. And associated with normal pressure, we have normal melting point and normal boiling point. Normal melting point is the phase transition between a solid to a liquid at normal pressure. And normal boiling point would just be the phase transition between a liquid to a gas at normal pressure. Now, how to be able to see that on this typical phase diagram? Well here is our normal pressure. And what I'm gonna do here is I'm going to trace to this blue line. Remember at this blue line is where we have the transition between solid to liquid. So this line is where melting can occur if we trace it down From there we hit 50°C, 50°C represents our normal melting point temperature. Now boiling has to do with us going from liquid to gas. So again, continuing tracing, We hit this red line here where vaporization can occur. And then you just trace down Here, we get 80°80° here would represent the normal boiling point of this substance. Right? So just remember the different types of phase change curves that are associated with any typical phase diagram. And remember if we know the normal pressure, we can apply that to find our normal melting point and our normal boiling point for any given substance.