The phase change that does not have a positive value for the change in entropy is an isothermal process. An isothermal process is a process where the temperature of the system remains constant. Since the temperature is constant, the entropy of the system does not change and thus the change in entropy is zero.
This means that an isothermal process does not have a positive value for the change in entropy.
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Which phase change does not increase entropy?
None of the four common phase changes – melting, evaporating, vaporizing, and condensing – increases entropy. However, they all have the potential to increase entropy depending on the context. For example, melting a solid increases its volume and surface area, increasing entropy by increasing disorder.
Similarly, vaporization results in higher entropy because it increases particle motion, as does evaporating and condensing if the phase changes occur rapidly enough. Generally speaking, phase changes do not increase entropy on their own, but the resulting changes in temperature, volume, and surface area can lead to an entropy increase.
Which of the following phase changes has a positive value for its entropy change?
The phase change with a positive value for its entropy change is vaporization. This is the process of a material changing from liquid to gas form. The entropy change in vaporization is positive because it involves an increase in the randomness of the particles in the system, thus releasing energy and increasing the disorder of molecules.
This release of energy causes an increase in entropy, creating a net positive change in the process. The increase in entropy during vaporization is ultimately what creates the pressure of the gas and allows it to expand and cool.
In which change in entropy is negative?
Entropy is a measure of the randomness or disorder of a system. When system entropy decreases, order increases and the energy of the system decreases. In this situation the change in entropy is negative.
Examples of processes or reactions that have a decrease in entropy include condensation, crystallization, sublimation, and endothermic reactions. Condensation occurs when a gas changes to a liquid, increasing the order of the system as the molecules are attracted and become closer together.
Crystallization increases the order of a system when a liquid condenses into a solid, forming distinct molecular structures. Sublimation is the transformation of a solid phase directly into a gas, with no liquid phase present.
This process demonstrates an increase in order as the molecules move further apart with the release of energy. Lastly, endothermic reactions occur when more energy is needed to break the bonds of reactants than is released from the forming products.
All these processes require an input of energy, resulting in a decrease in system entropy and order.
What phase has the least entropy?
The phase that has the least entropy is usually the ordered phase, such as a crystalline solid. In a crystalline solid, the atoms or molecules are arranged in an orderly, repeating pattern that exhibits low entropy due to the fact that the particles have less freedom of movement.
Additionally, because the particles are arranged in an ordered manner, the system is more organized and thus has a lower entropy. In contrast, the phase that has the highest entropy is usually the disordered, or amorphous phase, such as a liquid or gas.
In these phases, the particles are in chaotic and random motion, resulting in a higher degree of disorder and therefore higher entropy.
Is entropy change always positive?
No, entropy change is not always positive. Entropy change can be positive, negative, or zero depending on the system and the process associated with it. A change in entropy (ΔS) is positive when the system’s disorder increases, and is negative when the system’s disorder decreases.
The sign of ΔS will also depend on the direction of heat transfer. If heat is transferred from the system to the surroundings, the entropy change is positive. Conversely, if heat is transferred from the surroundings to the system, the entropy change is negative.
Furthermore, when there is no heat transfer between the system and the surrounding, ΔS will be zero. Hence, depending on the system and its associated process, entropy change can be positive, negative, or zero.
When entropy is negative is it exothermic or endothermic?
Entropy is a measure of the disorder of a system, and when entropy is negative it means that the disorder of the system has decreased. This implies that the energy of the system has decreased, making the reaction exothermic.
Exothermic reactions involve the release of energy, so when entropy is negative it indicates that energy is being released from the system. Essentially, when entropy is negative the reaction is exothermic.
What causes entropy to be positive or negative?
Entropy is a measure of the disorder of a system, and the Second Law of Thermodynamics states that the entropy of a closed system always increases over time. This increase in entropy is because energy is always dispersed or spread out and becomes less concentrated or available.
The amount and direction of entropy (positive or negative) is determined by how much energy is added to or taken away from the system. In general, when energy is added to a system, entropy will be positive (increased disorder); when energy is removed from a system, entropy will be negative (decreased disorder).
The processes by which this occurs are termed entropy-increasing (positive-entropy) processes and entropy-decreasing (negative-entropy) processes.
Examples of entropy-increasing processes include the mixing of two substances, the mixing of two gases, and the evaporation of a liquid, since energy is added in these instances. Examples of entropy-decreasing processes include displacement reactions, condensation, and crystal formation.
In each of these cases, energy is removed from the system, resulting in less disorder and a decrease in entropy.
Which one of the following phase changes decreases the entropy of the system?
The phase change which decreases the entropy of the system is the process of condensation. In the condensation process, molecules of a substance change from a gas phase to a liquid phase. When molecules enter the liquid phase, their energy levels increase and their movement decreases, resulting in an overall decrease in entropy.
As the molecules become tightly packed in the liquid phase, they cannot move freely as they could in the gas phase, thus decreasing the disorder within the system and leading to a decrease in entropy.
Additionally, the process of condensation requires energy to be absorbed by the system, which further contributes to the decrease in entropy.
Which process is an example of entropy decreasing quizlet?
The Second Law of Thermodynamics states that the entropy of an isolated system can never decrease over time. An example of a process in which entropy decreases is endothermic which is a process in which more energy is absorbed than released.
Endothermic processes occur when energy (heat) is transferred from the surroundings to the system, surprisingly not vice versa. An example of this is when a substance is placed in water, the water’s heat is transferred to the substance and causes the substance to dissolve.
This results in a decrease in entropy in the system, since the molecules in the system have become more ordered due to being dissolved in a solvent.
Under what condition can the entropy of a system be decreased quizlet?
The entropy of a system can only be decreased under certain conditions. These conditions are usually that the system will undergo a process which creates an order out of disorder, or a process that extracts heat from a colder body and transfers it to a hotter body.
As entropy is a measure of the disorder or randomness of a system, a decrease in entropy will signify a decrease in randomness and an increase in order. Therefore, the decrease in entropy is only possible if energy is being transferred out of the system.
For example, when using a refrigerator, energy is removed from the space inside the refrigerator, resulting in colder temperatures. In turn, this causes the entropy within the refrigerator to decrease as energy is removed from the system.
What are some examples of increasing or decreasing entropy in real life?
Entropy is an expression of disorder in a system, so examples of increasing or decreasing entropy in real life can be seen in most of our everyday activities. Increasing entropy would be seen in any activity that creates a greater level of randomness or uncertainty, such as randomizing a deck of playing cards or mixing a group of people to change the social dynamics of a room.
Decreasing entropy is observed when order is imposed, such as when organizing a closet or stacking books on a shelf.
At the molecular level, we can observe increasing entropy when energy is released during combustion, chemical reactions, and biological breakdowns. On the other hand, if energy is applied to something, less entropy is present.
For example, when an ice cube melts, the increased energy makes the random molecules of liquid water more ordered, decreasing entropy. Plants also decrease entropy when they take in energy from the Sun and convert it into usable energy through photosynthesis.
These are just a few examples of increasing and decreasing entropy as seen in our everyday lives and elsewhere in Nature.
How do you know if there is a decrease in entropy?
The decrease in entropy can be determined by looking at how the energy within a system is spread out. Hence the entropy of a system can be calculated mathematically by looking at how the energy of a system is arranged and distributed.
To be more specific, entropy is basically a measure of the disorder and randomness of a system, as well as how much energy is available for use within the system. Decreases in entropy occur when the energy of a system is more and more concentrated, or ordered.
This can take the form of a decrease in thermal energy, when the temperature of a system decreases, or an increase in the number of molecules that are found concentrated in a system. In all cases, decreases in entropy result in greater amounts of energy being available for use within the system.
Which change of phase is exothermic?
A phase change that is exothermic is one that absorbs heat from the surrounding environment. This means that an exothermic phase change releases energy to the environment in the form of heat. Examples of exothermic phase changes include the condensation of gas to liquid, the solidification or freezing of liquid to solid, and the sublimation of solid to gas.
All of these phase changes involve the release of energy from the atoms or molecules that are transitioning from one phase to another.
What are 3 exothermic reactions?
Exothermic reactions are chemical reactions that release energy, usually in the form of heat. Here are three examples of exothermic reactions:
1. Combustion Reactions: Combustion reactions involve the burning of a fuel in the presence of oxygen to produce heat energy. Typical fuels include wood, coal, oil, and natural gas. An example of a combustion reaction is the burning of methane: CH4 + 2O2 –> CO2 + 2H2O + energy.
2. Oxidation-Reduction Reactions: Oxidation-reduction reactions transfer electrons from one reactant to another, usually resulting in the release of energy. An example of such a reaction is the oxidation of iron: Fe + O2 –> Fe2O3 + energy.
3. Acid-Base Reactions: Acid-base reactions involve the transfer of a proton (H+) from one reactant to another. A classic example of this reaction is the neutralization of hydrochloric acid by sodium hydroxide: HCl + NaOH –> NaCl + H2O + energy.