What is the Third Law of Thermodynamics?

Summary

The Boomerang Nebula, at -272°C or 1 K, is the coldest known place in the universe, just above absolute zero. Despite advancements in cooling molecules to 500 nano Kelvins, absolute zero remains unattainable due to the second law of thermodynamics, which dictates heat transfer from warmer to cooler bodies. The third law of thermodynamics defines absolute zero as the point where a perfect crystal's entropy approaches zero. This theoretical concept is crucial for understanding entropy and temperature, and it underpins the practical applications of low-temperature research, such as solidifying gases like CO2 to create dry ice.

Takeaways

• 🌌 The Boomerang Nebula, located in the Centaurus constellation, is the coldest known place in the universe at -272 degrees Celsius, or 1 Kelvin, just above absolute zero.
• 🔬 Scientists on Earth have achieved even lower temperatures, cooling molecules to 500 nano Kelvins using lasers, yet absolute zero remains unattainable.
• ⚖️ The Third Law of Thermodynamics defines absolute zero as the point where the entropy of a perfect crystal approaches zero, highlighting the theoretical nature of this temperature.
• 🔥 The Second Law of Thermodynamics implies that absolute zero cannot be experimentally achieved because heat naturally flows from warmer to cooler bodies, preventing the complete cessation of molecular motion.
• 💠 Absolute zero can only theoretically be reached in a perfect crystal, where all atoms are identical and symmetrically arranged, minimizing entropy.
• 🔍 Any imperfections in a crystal or residual thermal energy prevent it from reaching the minimum entropy state, thus absolute zero is unattainable in practice.
• 🌡 The concept of absolute zero is crucial for understanding the limits of temperature and entropy, and the perpetual motion due to thermal energy.
• 🧪 James Dewar was a pioneer in low-temperature research, achieving a record low temperature by solidifying hydrogen gas, and postulating the limits of such experiments.
• 🔬 Walther Nernst's heat theorem, or the Third Law of Thermodynamics, has practical applications in gas storage and usage, such as the production of dry ice from carbon dioxide.
• ❄️ The process of solidifying gases like carbon dioxide and then releasing pressure to induce rapid temperature drops demonstrates the practical exploitation of thermodynamic principles.

Q & A

What is the coldest place in the universe?

The coldest place in the universe is the Boomerang Nebula in the Centaurus constellation.

What is the temperature of the Boomerang Nebula?

The temperature of the Boomerang Nebula is -272 degrees Celsius or 1 Kelvin, which is just one degree above absolute zero.

What is the record low temperature achieved on Earth?

On Earth, scientists have been able to cool individual molecules of sodium and potassium to 500 nano Kelvins using lasers.

What is the significance of absolute zero?

Absolute zero is significant because it is the temperature at which the entropy of a perfect crystal approaches zero, as defined by the third law of thermodynamics.

Why can't absolute zero be achieved experimentally?

Absolute zero cannot be achieved experimentally because, according to the second law of thermodynamics, heat will spontaneously move from a warmer body to a cooler body, causing the object being cooled to take in heat from its surroundings.

What is the relationship between entropy and temperature as described by the third law of thermodynamics?

The third law of thermodynamics states that the entropy of a perfect crystal approaches zero as the temperature approaches absolute zero.

What is a perfect crystal and why is it important in the context of absolute zero?

A perfect crystal is a structure where all atoms are identical and positioned in perfectly symmetrical ways. It is important because the lowest possible entropy can only occur in a perfect crystal, which is a theoretical concept at absolute zero.

How do imperfections in a crystal affect its entropy?

Imperfections in a crystal carry energy, which prevents the entropy from being minimized, thus making it impossible to achieve absolute zero.

What is the implication of not being able to reach absolute zero?

If we can't reach absolute zero, it means that nothing in the universe can be completely still, as there will always be some motion due to residual thermal energy.

Who was the first person to liquify and then solidify hydrogen gas, and what was the temperature achieved?

James Dewar was the first person to liquify and then solidify hydrogen gas, reaching a then record low temperature of 13 degrees above absolute zero.

What is the connection between the third law of thermodynamics and the storage and use of gases?

The third law of thermodynamics can be exploited when storing and using gases, such as reducing the entropy and temperature of carbon dioxide by solidifying it into a snow-like consistency, which can then be used to create dry ice.