Thermodynamic Equilibrium
Thermodynamic Equilibrium - Related Videos
02:38
Third Law of Thermodynamics
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2020
A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero. This limiting condition for a system’s entropy represents the third law of thermodynamics: the...
02:49
Second Law of Thermodynamics
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2020
In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
00:53
Second Law of Thermodynamics
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2019
The Second Law of Thermodynamics states that entropy, or the amount of disorder in a system, increases each time energy is transferred or transformed. Each energy transfer results in a certain amount of energy that is lost—usually in the form of heat—that increases the disorder of the surroundings. This can also be demonstrated in a classic food web. Herbivores harvest chemical energy from plants and release heat and carbon dioxide into the environment. Carnivores harvest the chemical energy...
00:37
First Law of Thermodynamics
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2019
The First Law of Thermodynamics states that energy cannot be created or destroyed, only transformed. This can be demonstrated within a classic food web where light energy from the sun is harnessed as radiant energy by plants, converted into chemical energy, and stored as complex carbohydrates. The vegetation is then consumed by animals and during the digestion process, the sugars release energy as heat. The sugars also produce chemical energy that either gets used up doing work, stored in...
02:16
First Law of Thermodynamics
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2020
Energy Conservation Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form after the change is completed. This observation is expressed in the law of conservation of energy: during a chemical or physical change, energy can be neither created nor destroyed, although it can be changed in form. According to the law of conservation of matter, there is no detectable change in the total amount of matter during a chemical...
FAQs
The three equilibrium requirements describe different possible sources of change. Thermal equilibrium addresses temperature differences, mechanical equilibrium concerns pressure-related effects, and chemical equilibrium concerns matter transfer or reaction through chemical-potential differences. A system can therefore satisfy one condition while still changing because another driving force remains. Considering all three prevents an incomplete assessment of its macroscopic stability.
Chemical potentials provide the criterion for whether matter has a net tendency to transfer or react. When the relevant chemical potentials are balanced, chemical processes no longer have a net driving force under the stated conditions. This concept helps explain both reversible reactions and how substances distribute themselves between coexisting phases, making it central to chemical equilibrium analysis.
The equilibrium framework connects a reaction’s direction with the system’s chemical state. If the composition does not correspond to the equilibrium condition, the remaining chemical driving force indicates that a net transformation can occur; at equilibrium, forward and opposing changes produce no net macroscopic reaction. This relationship also lets chemists relate the final composition to an equilibrium constant.
For systems containing multiple phases, equilibrium provides a way to evaluate whether the phases can coexist without a net transfer or transformation that changes the macroscopic state. Balanced chemical potentials are essential to this assessment. Consequently, thermodynamic equilibrium helps researchers analyze phase transitions, determine which phase arrangements are stable, and interpret substance distribution across coexisting phases.
Researchers examine whether the relevant macroscopic properties remain constant and whether any thermal, mechanical, or chemical driving force remains. They consider temperature and pressure uniformity where appropriate, along with chemical-potential balance and the absence of net reaction or matter transfer. This assessment links observable system behavior with the underlying equilibrium criteria rather than relying on composition alone.
The framework is useful whenever a process involves heat, pressure, chemical transformation, or more than one phase. It allows researchers to predict reaction direction, relate composition to equilibrium constants, and evaluate phase stability before designing or interpreting a process. These insights support analysis of systems in which energy and matter redistribution determine the attainable chemical state.