Second-order transition

Definition

A second-order transition is a type of phase change that occurs without a latent heat and is characterized by continuous changes in the first derivatives of thermodynamic potentials, such as volume or entropy, with respect to temperature or pressure. This transition involves changes in order parameters, like symmetry breaking, and can be associated with critical phenomena, where fluctuations occur at all length scales.

5 Must Know Facts For Your Next Test

1. Second-order transitions are characterized by smooth changes in properties like heat capacity and magnetization near the transition point.
2. Examples include the ferromagnetic to paramagnetic transition in materials and the superfluid transition in liquid helium.
3. At second-order transitions, properties such as susceptibility and heat capacity exhibit critical behavior, often diverging as they approach the transition temperature.
4. There is no latent heat involved in second-order transitions; thus, energy is absorbed or released continuously rather than in discrete amounts.
5. The concept of universality plays a crucial role in second-order transitions, meaning that systems with different microscopic details can exhibit similar critical behavior.

Review Questions

• Compare and contrast second-order transitions with first-order transitions in terms of thermodynamic properties.
  • Second-order transitions differ from first-order transitions primarily in that they do not involve latent heat and display continuous changes in thermodynamic properties. In first-order transitions, there are abrupt changes in properties like volume or entropy, leading to discontinuities in their derivatives. Conversely, during second-order transitions, properties such as heat capacity change smoothly and can even diverge as they approach the critical temperature.
• Discuss how order parameters are used to describe second-order transitions and provide an example.
  • Order parameters serve as a key tool for understanding second-order transitions by quantifying the degree of order present in a system as it changes phase. For instance, in the ferromagnetic to paramagnetic transition, the magnetization acts as an order parameter; below the critical temperature, it has a non-zero value indicating ordered alignment of magnetic moments, while above this temperature it approaches zero as the moments become disordered. This illustrates how order parameters help capture the essential features of phase changes.
• Evaluate the role of critical points in understanding second-order transitions and their significance in physical systems.
  • Critical points play a fundamental role in comprehending second-order transitions by marking the conditions at which distinct phases merge and exhibit similar properties. As systems approach these points, critical phenomena emerge where fluctuations occur across all scales, leading to universal behavior among different materials. This understanding is significant because it aids in predicting how various substances will behave under changing temperatures and pressures, informing practical applications such as material design and phase control in technology.

Related terms

first-order transition:

A first-order transition is a phase change that involves a latent heat, meaning there is a discontinuity in the first derivative of the thermodynamic potential, such as volume or entropy, with respect to temperature or pressure.

order parameter: An order parameter is a quantity used to describe the degree of order across a phase transition, reflecting changes in symmetry and helping to identify the type of transition.

critical point: A critical point is a specific condition (temperature and pressure) at which the properties of a substance undergo drastic changes, often related to second-order transitions, where the distinction between phases disappears.