Which phase change represents a decrease in entropy?

Asked By: Ynes Mendracabeitia | Last Updated: 11th April, 2020
Category: science chemistry
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Explanation: Entropy decreases when the number of moles of gas decreases during a reaction. In the case of the correct answer, the number of moles of gas decreases from two to one. When a substance goes from a solid to a gas (sublimation) or from a liquid to a gas (evaporation), entropy increases.

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In respect to this, which reaction would cause a decrease in entropy?

In an exothermic reaction, the external entropy (entropy of the surroundings) increases. In an endothermic reaction, the external entropy (entropy of the surroundings) decreases.

Secondly, which sample has lowest entropy? Solids have the fewest microstates and thus the lowest entropy.

Likewise, is condensation a decrease in entropy?

A phase change from a liquid to a solid (i.e. freezing), or from a gas to a liquid (i.e. condensation) results in an decrease in the disorder of the substance, and a decrease in the entropy.

When ice melts Does entropy increase or decrease?

At the higher temperature, the reaction is not feasible as the entropy of the reaction is decreasing. However, ice will melt at this temperature, as the entropy increases : Both the processes of ice melting at 10oC and water freezing at -10oC are spontaneous reactions; they can occur.

39 Related Question Answers Found

How do you know if enthalpy increases or decreases?

The heat that passes into or out of the system during a reaction is the enthalpy change. Whether the enthalpy of the system increases (i.e. when energy is added) or decreases (because energy is given off) is a crucial factor that determines whether a reaction can happen.

What factors affect entropy?

energy within a system. The entropy of a substance increases with its molecular weight and complexity and with temperature. The entropy also increases as the pressure or concentration becomes smaller. Entropies of gases are much larger than those of condensed phases.

What does a negative entropy mean?

Entropy is the amount of disorder in a system. Negative entropy means that something is becoming less disordered. In order for something to become less disordered, energy must be used. The second law of thermodynamics states that the world as a whole is always in a state of positive entropy.

What does entropy depend on?

Energy and Entropy
Entropy is a measure of the random activity in a system. The entropy of a system depends on your observations at one moment. How the system gets to that point doesn't matter at all. If it took a billion years and a million different reactions doesn't matter.

How is enthalpy and entropy related?


Enthalpy ( H ) is defined as the amount of energy released or absorbed during a chemical reaction. Entropy ( S ) defines the degree of randomness or disorder in a system. Therefore, the free energy expression provides a relationship between enthalpy and entropy.

How do you predict entropy change?

Entropy increases as you go from solid to liquid to gas, and you can predict whether entropy change is positive or negative by looking at the phases of the reactants and products. Whenever there is an increase in gas moles, entropy will increase.

Does entropy decrease energy decreases?

Entropy is the loss of energy available to do work. Another form of the second law of thermodynamics states that the total entropy of a system either increases or remains constant; it never decreases. Entropy is zero in a reversible process; it increases in an irreversible process.

What is a decrease in entropy?

When water freezes its entropy decreases. This does not violate the second law of thermodynamics. Entropy can decrease somewhere, provided it increases somewhere else by at least as much. The entropy of a system decreases only when it interacts with some other system whose entropy increases in the process.

Does boiling increase entropy?

When the water boils, the entropy change is quite large (ΔSvaporization = 109 J/mol K), as the molecules go from being relatively constrained in the liquid to gas molecules that can fly around. At temperatures lower than the boiling point, the enthalpy term predominates and ΔG is positive.

What is concept of entropy?


Entropy, the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, the amount of entropy is also a measure of the molecular disorder, or randomness, of a system.

How do I calculate entropy?

Key Takeaways: Calculating Entropy
  1. Entropy is a measure of probability and the molecular disorder of a macroscopic system.
  2. If each configuration is equally probable, then the entropy is the natural logarithm of the number of configurations, multiplied by Boltzmann's constant: S = kB ln W.

What phase changes increase entropy?

The phases of matter in order of increasing entropy are solid, liquid, then gas. The processes that increase entropy by changing phases will cause a phase transition from lower entropy to higher entropy. These transitions are melting (solid to liquid), vaporization (liquid to gas), and sublimation (solid to gas).

How do you define enthalpy?

Enthalpy is a thermodynamic property of a system. It is the sum of the internal energy added to the product of the pressure and volume of the system. It reflects the capacity to do non-mechanical work and the capacity to release heat. Enthalpy is denoted as H; specific enthalpy denoted as h.

What is r in Gibbs free energy?

Free energy and Equilibrium Constants
G = standard-state free energy. R = ideal gas constant = 8.314 J/mol-K. T = temperature (Kelvin)

Is sugar dissolving in hot water spontaneous?


A spontaneous process is a process that occurs without outside intervention. If a process is spontaneous, the reverse process is not spontaneous. For instance, a sugar cube will spontaneously dissolve in hot water, but dissolved sugar will not spontaneously separate from the water to form a sugar cube.

Is condensation an increase in entropy?

Vaporization is endothermic (uphill in energy), and this transition leads to an increase in entropy. The reverse transition of a gas going to a liquid is condensation. Since condensation is simply the reverse of vaporization, the changes in enthalpy and entropy will be exactly the same, but opposite in sign.

What state has the highest entropy?

Explanation: Entropy by definition is the degree of randomness in a system. If we look at the three states of matter: Solid, Liquid and Gas, we can see that the gas particles move freely and therefore, the degree of randomness is the highest.