# Difference between revisions of "Critical Point"

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'''Definition: Critical Point''' | '''Definition: Critical Point''' | ||

− | The Critical Point indicates the Chi value that separates the situation where mixtures are always stable and the situations where mixtures are unstable or metastable where the resultant mixtures then separate into components (eventually if metastable and instantly is unstable). | + | The Critical Point indicates the Chi value ''X'' (Chi is an energy of interaction parameter) that separates the situation where mixtures are always stable and the situations where mixtures are unstable or metastable where the resultant mixtures then separate into components (eventually if metastable and instantly is unstable). |

'''Example Discussion of the Critical Point''' | '''Example Discussion of the Critical Point''' | ||

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''For AP225 students, this discussion is based on the diagrams used in the course notes'' | ''For AP225 students, this discussion is based on the diagrams used in the course notes'' | ||

− | The critical point is where the spinodal line and the coexist curve are equal ([[Image:Spinodal1.jpg]] as defined in the Jones text used in Soft Matter AP225). The critical point is where the ''either a stable or unstable solution can occur'' ( | + | The critical point is where the spinodal line and the coexist curve are equal ([[Image:Spinodal1.jpg]] as defined in the Jones text used in Soft Matter AP225). The critical point is where the ''either a stable or unstable solution can occur'' (''X''=2 in figures below). At the critical point the free energy of the system is a straight line with no minima; at any ''X'' less than 2, no contribution is given to the production of the diagram on the left (below) |

− | + | [[Image:CriticalPoint1.jpg]] | |

Reference: | Reference: | ||

[[The Science of Chocolate: interactive activities on phase transitions, emulsification, and nucleation]] | [[The Science of Chocolate: interactive activities on phase transitions, emulsification, and nucleation]] |

## Revision as of 00:55, 7 December 2011

Entry by Andrew Capulli

**Definition: Critical Point**

The Critical Point indicates the Chi value *X* (Chi is an energy of interaction parameter) that separates the situation where mixtures are always stable and the situations where mixtures are unstable or metastable where the resultant mixtures then separate into components (eventually if metastable and instantly is unstable).

**Example Discussion of the Critical Point**

*For AP225 students, this discussion is based on the diagrams used in the course notes*

The critical point is where the spinodal line and the coexist curve are equal ( as defined in the Jones text used in Soft Matter AP225). The critical point is where the *either a stable or unstable solution can occur* (*X*=2 in figures below). At the critical point the free energy of the system is a straight line with no minima; at any *X* less than 2, no contribution is given to the production of the diagram on the left (below)

Reference: