Fase (stof)

• Gasform, "luftformigt"
• Flydende form
• Fast form
• Plasma form

Table of contents

1 Definition 2 Fasediagram 3 Anvendelse 4 Se også 5 Eksterne henvisninger

Definition

Når et system går fra en fase til en anden, vil der generelt være et hop eller knæk, hvor den frie energi er ikke-analytisk. Dette benævnes en faseovergang, faseskift. Almindelige kendte faseovergange er smeltning (fast til flydende) og fortætning (kondensation, gas til flydende). Grundet denne ikke-analytiske, vil den frie energi på begge sider af faseskiftet være 2 forskellige analytiske funktioner, så en eller flere termodynamiske egenskaber vil opføre sig meget anderledes efter faseskiftet.

Den mest undersøgte termodynamiske egenskab er varmekapacitet. Ved et faseskift vil varmekapacitetsgrafen enten gå mod uendelig, hoppe til en anden værdi eller knække (en af funktionens afledede vil være diskontinuert).

Mulige varmekapacitetsgrafer (C) som funktion af temperaturen (T) ved et faseskift.

Fasediagram

Et typisk fasediagram.

Anvendelse

• Plasma (ioniseret gas)
• Gasform, "luftformigt"
• Flydende form
• Superflydende faststof (kilde: 2 September 2004, physicsweb: Evidence for supersolid is firmed up)
• Fast form Faststof
• Bose-Einstein kondensat
• Fermionisk kondensat

• Neutronstjerne - En neutronstjernes massefylde antages at være tæt på atomkerners og neutroners.
• Kvarkstjerne - En kvarkstjernes massefylde antages at være højere end neutronstjerners og dermed atomkerners og neutroners.

• Fysik, kvantemekanik, faststoffysik, entropi, exergi

Eksterne henvisninger

• 25.04.2002 Ing.dk: Ny form for materiale fundet i universet
• Science Daily, 2003-10-10: Metallic Phase For Bosons Implies New State Of Matter
• Fagenes Infoguide: Ungdomsuddannelser - Faststoffysik
• 2004-11-19, Sciencedaily: Unusual Material That Contracts When Heated Is Giving Up Its Secrets To Physicists
• 2004-01-15, ScienceDaily: Probable Discovery Of A New, Supersolid, Phase Of Matter Citat: "...We apparently have observed, for the first time, a solid material with the characteristics of a superfluid...but because all its particles are in the identical quantum state, it remains a solid even though its component particles are continually flowing..."
• 29 January, 2004, BBC News: New form of matter created in lab Citat: "...The new matter is the sixth known form of matter after solids, liquids, gasses, plasma and a Bose-Einstein condensate..."
  • 2004-01-29, Sciencedaily: NIST/University Of Colorado Scientists Create New Form Of Matter: A Fermionic Condensate
• Number 671 #1, January 30, 2004, AIP: Halfway Across the BEC-BCS Prairie Citat: "...describes the new NIST state as "a dramatic new sort of fermionic condensate, basically Cooper pairing in the strong-field limit."..."
• 2 September 2004, physicsweb: Evidence for supersolid is firmed up Citat: "...However, many of the details of the experiment are not yet understood. In an accompanying article Tony Leggett of the University of Illinois in Urbana writes that the experiment "will force theorists to revise dramatically the generally accepted picture of crystalline solid helium-4."..."
  • 14 January 2004, physicsweb: Supersolid is seen in the lab Citat: "...Eun-Seong Kim and Moses Chan of Pennsylvania State University say their supersolid behaves like a superfluid – a liquid that flows without resistance - but has all the characteristics of a crystalline solid (E Kim and M H W Chan 2004 Nature 427 225)..."
• 24 September 2004, physicsweb: Law-breaking liquid defies the rules Citat: "...Marie Plazanet and colleagues at the Université Joseph Fourier and the Institut Laue-Langevin, both in Grenoble, found that a simple solution composed of two organic compounds becomes a solid when it is heated to temperatures between 45 and 75°C, and becomes a liquid when cooled again..."

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