PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Physical Chemistry → Thermodynamics ↓


Laws of Thermodynamics


The laws of thermodynamics are fundamental principles that explain how energy moves and changes in the universe. These laws are very important in science because they help us understand processes in physics and chemistry, especially in systems where heat and work are involved. In chemistry, they explain how reactions occur, why some are spontaneous, and how energy is conserved. This explanation will cover each law in detail, providing visual and textual examples to aid understanding.

Zeroth law of thermodynamics

The zeroth law of thermodynamics establishes the concept of temperature. It is expressed as:

If system A is in thermal equilibrium with system C, and system B is in thermal equilibrium with system C, then system A and system B are in thermal equilibrium with each other.

In simple terms, if two systems are each in equilibrium with a third system, then they are in equilibrium with each other. This law allows us to measure temperature because it implies that temperature is a property that can define thermal equilibrium. Consider three cups of water A, B, and C, all at different temperatures. When you mix them, if A and C reach equilibrium, and B and C reach equilibrium, then A and B will also be in equilibrium. This concept is foundational because it means that temperature can be considered a meaningful property across different systems.

System A System B System C

First law of thermodynamics

The first law of thermodynamics is also called the law of conservation of energy. It states:

Energy can neither be created nor destroyed, it can only be converted from one form to another.

This law implies that the total energy of an isolated system remains constant, although it may change form, such as from chemical energy to thermal energy and vice versa. The first law is often expressed mathematically for a system as follows:

ΔU = Q - W

Where:

  • ΔU: change in the internal energy of the system
  • Q: heat added to the system
  • W: work done by the system

Consider a simple gasoline engine. The chemical energy of the gasoline is converted into mechanical energy to drive the parts, and thermal energy as heat. Here is a textual example:

  • An engine absorbs 300 joules of heat energy, and does 150 joules of work. According to the first law, the change in internal energy is:
ΔU = Q - W = 300 J - 150 J = 150 J

This means that the internal energy of the system increased by 150 joules.

Second law of thermodynamics

The second law of thermodynamics is somewhat abstract. It introduces the concept of entropy. A general expression of this law is:

In all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state. This is also stated as: Entropy tends to increase.

Entropy can generally be considered a measure of disorder. This law implies that natural processes tend to move toward a state of maximum disorder. A common way to understand this is to consider the efficiency of a heat engine. A heat engine cannot convert all the heat energy it absorbs into work. Part of it will inevitably increase the entropy of the universe. Consider the example of melting ice. When ice (structured, low entropy) melts into water (less structured, high entropy), the process is spontaneous and increases the overall entropy of the system.

Ice (low entropy) Water (high entropy)

In a man-made process like refrigeration, we work against this natural tendency. We remove heat from a system (such as a refrigerator) in order to decrease the entropy of its contents, but by doing so we also increase the entropy of the surroundings by removing heat.

Third law of thermodynamics

The third law of thermodynamics deals with the absolute behavior of systems that reach absolute zero temperature. It states:

As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum value.

In essence, this suggests that it is impossible to reach absolute zero in a finite number of steps. At absolute zero, a perfect crystal has minimal entropy because its structure is completely ordered. A more intuitive way to think about this is through quantum mechanics, where particles at absolute zero would theoretically have only one microstate available, leading to minimal entropy.

Perfect Crystal

A common example is a crystalline lattice. As the temperature falls, the vibrations of the atoms diminish, and at absolute zero, ideally, they stop completely, leaving only the underlying quantum mechanical state. In practical terms, this affects thermodynamic calculations and helps determine reference points for entropy measurements. This understanding of entropy and minimum entropy at absolute zero supports interpretations of other laws by providing a base state or reference point for discussing changes in entropy.

Conclusion

The four laws of thermodynamics underlie an incredible range of phenomena in physics and chemistry. They explain why processes occur, what their efficiency is, and even determine the boundaries of energy transitions. Although abstract, their implications are enormous, governing everything from microscopic interactions in chemistry to the enormous energies of stellar life cycles.

Ultimately, these laws reflect the deeper reality of energy behavior in the universe, guiding scientists and chemists in understanding and practically using energy in various forms, from chemical reactions to industrial processes. This exploration provides insight into how the universe conserves energy, how energy dissipates entropy, and why perfect order (absolute zero) is theoretically unattainable in practice.


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Laws of Thermodynamics

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