# 17 Third Law of Thermodynamics Examples in Real Life

The third law of thermodynamics states that as the temperature of a system approaches absolute zero (0 Kelvin), the entropy of the system approaches a minimum value, often considered to be zero. In other words, as a system gets colder and colder, its entropy, which is a measure of the system’s disorder or randomness, decreases and approaches a constant minimum value.

Mathematically, the third law of thermodynamics is expressed as:

S – S0 = 𝑘B ln𝛀

Where,

• S is the entropy of the system.
• S0 is the initial entropy.
• 𝑘B denotes the Boltzmann constant.
• 𝛀 is the total number of microstates consistent with the system’s macroscopic configuration.

Now, the third law of thermodynamics also implies that at absolute zero, a crystalline substance would have zero entropy. Hence, the value of 𝛀 = 1 (for a perfect crystal with exactly one unique ground state), and the equation becomes:

S – S0 = 𝑘B ln(1) = 0

Now, with the initial entropy of the system as zero, the entropy of the system becomes zero:

S – 0 = 0 ⇒ S = 0

Thus, the entropy of a perfect crystal at absolute zero is zero.

While the third law of thermodynamics may seem like a theoretical concept, its implications are observed in various real-life phenomena, particularly in the study of extreme temperatures and the behaviour of matter at very low temperatures. It provides insights into the behaviour of matter at low temperatures and helps researchers and engineers design and understand systems that operate under such conditions. Here are some of the most significant third law of thermodynamics examples in real life:

## Examples

### 1. Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) machines rely on superconductors and the principles of the third law of thermodynamics for their precision. Within an MRI machine, powerful superconducting magnets generate the magnetic fields essential for imaging. To maintain their superconducting state and operate effectively, these magnets need to be cooled to extremely low temperatures. This cooling process is crucial because superconductivity emerges when certain materials experience extreme cold, leading to zero electrical resistance. Liquid helium is commonly used as a cryogenic coolant for this purpose. By cooling the magnets to temperatures near absolute zero, the MRI machine ensures that electrical currents can flow without resistance, creating a stable and powerful magnetic field. This superconducting state enables the generation of detailed and high-resolution images of the body’s internal structures. Here the third law of thermodynamics is evident as the temperature approaches its absolute minimum, resulting in minimal entropy and optimal conditions for maintaining the superconducting state.

### 2. Cryopreservation

Cryopreservation is a vital technique used in preserving biological materials by subjecting them to extremely low temperatures. One significant application is found in fertility clinics, where sperm, eggs, and embryos are stored at sub-zero temperatures to maintain their viability for future use. This process enables individuals or couples to preserve reproductive cells when fertility is at its peak, providing an option for later use in assisted reproductive technologies like in vitro fertilization. By cooling these biological materials to temperatures near absolute zero, the metabolic and cellular activities slow down, effectively halting any deterioration. This safeguards the genetic integrity of the stored materials, ensuring their potential to result in successful pregnancies when used in the future. Obeying the third law of thermodynamics, where entropy approaches a minimum at extremely low temperatures, ensures the success of cryopreservation in maintaining the delicate balance of life at the cellular level, opening new possibilities for individuals and couples on their journey to parenthood.

### 3. Cold Storage of Vaccines

To preserve their effectiveness, it is essential to store vaccines at low temperatures. This cold storage process prevents the degradation of the vaccine’s active components, maintaining their structural integrity and ensuring they remain capable of triggering the desired immune response. Different vaccines may require specific temperature ranges for storage, commonly ranging from refrigeration temperatures to ultra-low freezing temperatures. Adherence to this cold storage protocol is imperative to extend the shelf life of vaccines, allowing them to remain viable for administration over an extended period. The efficient temperature control aligns with the principles of the third law of thermodynamics, where lower temperatures reduce the molecular motion and, consequently, the likelihood of chemical reactions that could compromise the vaccine’s efficacy.

### 4. High-Altitude Aviation

At high altitudes, temperatures can drop significantly, exposing the aircraft to colder conditions. This temperature decrease can affect the properties of materials, potentially making them more brittle and susceptible to structural changes. Engineers and designers in aviation must account for these variations, selecting materials that can withstand the extreme temperatures encountered during high-altitude flights. The principles of the third law of thermodynamics become crucial in ensuring the reliability and safety of aircraft components. As temperatures approach absolute zero, the behaviour of materials becomes more predictable, and understanding these thermodynamic principles aids in designing aircraft that can endure the challenges of high-altitude environments.

### 5. Cold-Weather Materials Testing

Cold-weather materials testing is an indispensable part of creating durable and resilient structures and equipment capable of withstanding the challenges presented by severe cold conditions, ensuring the safety and reliability of these elements in various applications. This testing is particularly essential for structures like bridges, vehicles including automobiles and aircraft, and various types of equipment used in cold regions. The goal is to prevent material failures, fractures, or degradation that could compromise the integrity and safety of these elements. As engineers aim to understand how materials behave as temperatures approach absolute zero, the significance of the third law of thermodynamics becomes evident. By gaining insights into the thermodynamic properties of materials in extreme cold, engineers can make informed decisions during the design and construction phases.

### 6. Space Exploration

Spacecraft components are exposed to extreme temperature variations as they move between areas illuminated by the sun and those in the shadow of celestial bodies. Engineers and scientists must carefully design spacecraft materials and systems to withstand these temperature extremes. Understanding the principles of thermodynamics, including the third law, is essential in predicting how materials behave in these harsh conditions. Approaching temperatures close to absolute zero, components need to resist becoming too brittle or experiencing structural changes that could compromise their functionality. Effective insulation and thermal control systems are employed to regulate temperatures within acceptable limits, preventing overheating or freezing of critical components.

### 7. Astrophysics

In the field of astrophysics, the study of black holes involves a deep exploration of the thermodynamics of matter in their vicinity, where conditions are extreme. The temperatures near black holes can vary widely, reaching extremes that challenge our understanding of the behaviour of matter. As matter spirals into a black hole, it undergoes intense compression and heating, giving rise to extreme temperatures. Understanding the thermodynamics of this matter is crucial in unravelling the mysteries of black holes and their impact on the surrounding space. The principles of thermodynamics come into play as scientists seek to comprehend the behaviour of matter near these celestial objects. As temperatures approach extreme values, the entropy and thermal properties of matter become critical considerations. Researchers delve into the complexities of how materials respond to the gravitational forces and extreme temperatures near black holes, shedding light on the fundamental nature of the universe.

### 8. Deep-Sea Exploration

The principles of thermodynamics play a pivotal role in comprehending how materials and fluids respond to the extreme cold and pressure of deep-sea environments. Engineers and scientists carefully consider the thermodynamic properties of materials used in the construction of submersibles and equipment, ensuring their durability and functionality under these challenging circumstances. The application of thermodynamic principles in deep-sea exploration not only advances our knowledge of the ocean’s depths but also enables the development of robust technologies that can withstand the extreme conditions encountered during underwater exploration.

### 9. Liquid Nitrogen in Food Processing

The application of liquid nitrogen in food processing aligns with the principles of the third law of thermodynamics as it approaches temperatures close to absolute zero. Flash freezing with liquid nitrogen offers several advantages, including the preservation of the natural texture, flavours, and nutritional content of the food. By minimizing the formation of ice crystals, this method helps maintain the integrity of fruits, vegetables, and other perishable items. The rapid freezing also reduces the risk of freezer burn and extends the shelf life of the products. .

### 10. Dilution Refrigerators

In condensed matter physics, researchers use dilution refrigerators to investigate phenomena like superconductivity, quantum phase transitions, and novel electronic states that manifest at ultra-low temperatures. The working principle of dilution refrigerators is rooted in the third law of thermodynamics, which describes the behaviour of systems as they approach absolute zero. These refrigerators rely on the dilution of isotopes, typically helium-3 and helium-4, to achieve temperatures close to absolute zero. By exploiting the properties of quantum fluids, dilution refrigerators can cool samples to temperatures as low as a few thousandths of a degree above absolute zero.

### 11. Laboratory Freezers

Laboratory freezers are indispensable tools in scientific research, providing a controlled environment for maintaining ultra-low temperatures essential for the long-term storage of biological samples, chemicals, and reagents. These freezers operate on principles derived from thermodynamics, ensuring that temperatures are sustained at levels necessary for preserving the integrity and functionality of sensitive materials. The third law of thermodynamics comes into play as these freezers aim to approach absolute zero, minimizing molecular motion and thereby slowing down degradation processes. In laboratories, biological samples like DNA, enzymes, and tissues, as well as various chemicals and reagents, are stored in these ultra-low temperature freezers to extend their viability and usefulness over extended periods.

### 12. Helium Cooling in Particle Accelerators

Helium cooling plays a crucial role in the operation of particle accelerators, specifically in maintaining the superconductivity of magnets. To achieve and sustain superconductivity, the magnets must be cooled to extremely low temperatures, close to absolute zero. Helium, a cryogenic coolant, is employed for this purpose. As the temperature drops, helium undergoes a phase transition, becoming a superfluid with remarkable heat-carrying capacity. This superfluid helium efficiently extracts heat generated during the operation of the magnets, preventing them from overheating and maintaining the conditions necessary for superconductivity. Following the principles of the third law of thermodynamics, where entropy approaches a minimum as temperature decreases, this process ensures the magnets operate with minimal resistance, enabling precise control of particle beams in accelerator experiments.

### 13. Superconducting Maglev Trains

Unlike traditional trains, Maglev trains utilize superconducting magnets that hover above the tracks, eliminating the need for physical contact and reducing friction to virtually zero. The superconducting magnets, when cooled to extremely low temperatures, enter a state of zero electrical resistance, known as superconductivity. This ensures that the magnetic levitation remains stable and the train experiences minimal friction as it moves along the track. The application of superconducting Maglev technology exemplifies the integration of physics and engineering to address challenges in transportation, offering a sustainable and high-speed alternative that aligns with the principles of the third law of thermodynamics.

### 14. Quantum Computing

Quantum computers harness the unique properties of quantum mechanics to process information, and qubits are the fundamental units of quantum information. The application of the third law of thermodynamics in quantum computing highlights the significance of temperature control in harnessing the full potential of qubits. By approaching absolute zero, scientists and engineers aim to minimize the disruptive effects of thermal fluctuations, paving the way for advancements in quantum computation and information processing. As the temperature of a quantum computer approaches absolute zero, qubits exhibit behaviour governed by the third law of thermodynamics. At temperatures close to absolute zero, the entropy of a system approaches a minimum, and the quantum states of qubits become more stable. In the pursuit of building powerful and efficient quantum computers, researchers strive to manipulate and control qubits with precision. Cooling these quantum systems to ultra-low temperatures, often achieved through methods like dilution refrigeration, reduces thermal noise and enhances the coherence of qubits. This process allows quantum computers to perform complex calculations and simulations that classical computers would struggle to execute efficiently.

### 15. Cosmic Microwave Background Radiation

Cosmic microwave background (CMB) radiation is a faint glow that permeates the entire cosmos, originating from the hot, dense conditions of the early universe. The principles of the third law of thermodynamics play a significant role in interpreting these temperature fluctuations. As the universe expanded and cooled, leaving imprints on the CMB, the third law came into play, influencing the entropy and thermal characteristics of the cosmic background radiation. The analysis of these temperature fluctuations allows scientists to map the distribution of matter in the early universe and understand the formation of cosmic structures like galaxies and galaxy clusters.

### 16. Isotope Separation

Isotope separation, a crucial process in nuclear technology, involves the utilization of cryogenic methods, particularly in the production of enriched uranium for nuclear reactors. Cryogenic techniques, operating at extremely low temperatures, play a pivotal role in the separation of isotopes due to the distinct mass differences between isotopes. By cooling the uranium hexafluoride gas, commonly used in isotope separation processes, the lighter uranium-235 molecules have a higher probability of diffusing or moving faster than the heavier uranium-238 molecules. This difference in molecular motion allows for the separation of uranium isotopes, with the enriched uranium collected for further processing.

### 17. Formation of Bose-Einstein Condensates

The formation of Bose-Einstein condensates (BECs) stands as a remarkable achievement in the field of experimental physics, involving the cooling of atoms to temperatures near absolute zero. At such extremely low temperatures, typically just a fraction above absolute zero, individual atoms lose their distinct identities and collectively enter a state of quantum coherence, behaving as a single, indistinguishable entity. This phenomenon, predicted by Satyendra Nath Bose and Albert Einstein in the early 20th century, offers a unique glimpse into the quantum realm of matter. The cooling process in the creation of BECs is a testament to the principles of the third law of thermodynamics as the temperature approaches the absolute minimum.