entropy

Examples of entropy in the following topics:

• Struggle against entropy

• Standard Entropy

  • The standard entropy of a substance (its entropy at 1 atmospheric pressure) helps determine if a reaction will take place spontaneously.
  • The standard entropy of a substance is its entropy at 1 atm pressure.
  • Some typical standard entropy values for gaseous substances include:
  • It is apparent that entropies generally increase with molecular weight.
  • There is an inverse correlation between the hardness of a solid and its entropy.

• Order to Disorder

  • Entropy is a measure of disorder, so increased entropy means more disorder in the system.
  • Entropy is a measure of disorder.
  • There is a large increase in entropy in the process.
  • The mixing decreases the entropy of the hot water but increases the entropy of the cold water by a greater amount, producing an overall increase in entropy.
  • Entropy is a measure of disorder.

• The Third Law

  • Entropy is related to the number of possible microstates, and with only one microstate available at zero kelvin the entropy is exactly zero.
  • Nernst proposed that the entropy of a system at absolute zero would be a well-defined constant.
  • This law provides an absolute reference point for the determination of entropy. ( diagrams the temperature entropy of nitrogen. ) The entropy (S) determined relative to this point is the absolute entropy represented as follows:
  • Temperature–entropy diagram of nitrogen.
  • Absolute value of entropy can be determined shown here, thanks to the third law of thermodynamics.

• Changes in Energy

  • For isolated systems, entropy never decreases.
  • Increases in entropy correspond to irreversible changes in a system.
  • The entropy of a system is defined only if it is in thermodynamic equilibrium.
  • However, the entropy of the system of ice and water has increased more than the entropy of the surrounding room has decreased.
  • Ice melting in a warm room is a common example of increasing entropy.

• Living Systems and Evolution

  • It is possible for the entropy of one part of the universe to decrease, provided the total change in entropy of the universe increases.
  • But it is always possible for the entropy of one part of the universe to decrease, provided the total change in entropy of the universe increases.
  • How is it possible for a system to decrease its entropy?
  • However, there is a large total increase in entropy resulting from this massive heat transfer.
  • Formulate conditions that allow decrease of the entropy in one part of the universe

• Microstates and Entropy

  • With more available microstates, the entropy of a system increases.
  • As a result, entropy (denoted by S) is an expression of disorder or randomness.
  • With more available microstates, the entropy of a system increases.
  • This is the basis of an alternative (and more fundamental) definition of entropy:
  • Therefore, the entropy of a solid is less than the entropy of a liquid, which is much less than the entropy of a gas:

• The Third Law of Thermodynamics and Absolute Energy

  • Specifically, the entropy of a pure crystalline substance at absolute zero temperature is zero.
  • Entropy is related to the number of possible microstates according to $S = k_Bln(\Omega)$, where S is the entropy of the system, kB is Boltzmann's constant, and Ω is the number of microstates (e.g. possible configurations of atoms).
  • The constant value (not necessarily zero) is called the residual entropy of the system.
  • The entropy determined relative to this point (absolute zero) is the absolute entropy.
  • The entropy (S) of a substance (compound or element) as a function of temperature (T).

• Solutions and Entropy Changes

  • Chemists use the term "entropy" to denote this aspect of molecular randomness.
  • Entropy is indeed a fascinating, but somewhat confusing, topic.
  • In a similar manner entropy plays an important role in solution formation.
  • All these factors increase the entropy of the solute.
  • This is the same as saying that the entropy of the solute increases.

• Changes in the Entropy of Surroundings

  • Irreversible reactions result in a change in entropy to the surroundings.
  • The heat from the surroundings (entropy) goes into the ice water and the ice melts.
  • The entropy of the ice water increases while the entropy of the surroundings decreases.
  • Distinguish whether or not entropy of surroundings changes in various reactions