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.

Outlines

00:00

🌌 The Quest for Absolute Zero

This paragraph delves into the concept of absolute zero, the theoretical limit of temperature where molecular motion ceases. It highlights the Boomerang Nebula as the coldest known place in the universe at -272 degrees Celsius, just one degree above absolute zero. The text also discusses the experimental challenges of reaching absolute zero, as per the second law of thermodynamics, which dictates that heat naturally flows from warmer to cooler bodies. Despite these challenges, absolute zero remains a crucial theoretical concept, defining the point where a perfect crystal's entropy approaches zero. The paragraph further explains that any imperfections or residual thermal energy within a crystal prevent it from achieving the minimum entropy state. It concludes by discussing the historical context of low-temperature research, mentioning James Dewar's work on liquefying hydrogen and Walther Nernst's formulation of the third law of thermodynamics, which has practical applications in gas storage and usage.

Keywords

💡Boomerang Nebula

The Boomerang Nebula is a cloud of gas and dust that is the coldest known spot in the universe, as mentioned in the script. It is located in the Centaurus constellation and has a temperature of -272 degrees Celsius, or 1 Kelvin, which is just one degree above absolute zero. This nebula is a key example in the video's discussion of extreme low temperatures and serves to illustrate the limits of what can be achieved in terms of cooling.

💡Absolute Zero

Absolute zero is a theoretical limit of temperature where molecular motion ceases, as defined by the third law of thermodynamics. It is -273.15 degrees Celsius or 0 Kelvin. The script explains that reaching absolute zero is impossible due to the second law of thermodynamics, which states that heat naturally flows from warmer to cooler bodies, preventing the achievement of absolute zero. This concept is central to the video's exploration of temperature and entropy.

💡Entropy

Entropy, as discussed in the video, is a thermodynamic property that represents the degree of disorder or randomness in a system. The third law of thermodynamics ties entropy to absolute zero, stating that the entropy of a perfect crystal approaches zero at absolute zero temperature. Entropy is a key concept in understanding the limitations of cooling processes and the natural tendency towards disorder in the universe.

💡Thermodynamics

Thermodynamics is the study of heat and its conversion to and from other forms of energy. The script references the first, second, and third laws of thermodynamics to explain the behavior of heat and the challenges in achieving extreme low temperatures. These laws provide the theoretical framework for the video's discussion on the limits of cooling and the properties of matter at low temperatures.

💡Lasers

Lasers are used in the script as an example of a technology that can cool individual molecules to extremely low temperatures. Scientists have used lasers to cool sodium and potassium molecules to 500 nano Kelvins, showcasing the potential of laser technology in achieving temperatures colder than those found in the Boomerang Nebula. This example illustrates the practical applications of thermodynamics in achieving extreme low temperatures.

💡Sodium and Potassium

Sodium and potassium are elements that were specifically mentioned in the script as being cooled to 500 nano Kelvins using lasers. These elements are used to demonstrate the practical limits of cooling techniques and the challenges in reaching absolute zero. The script uses these elements to illustrate the scientific experiments that push the boundaries of our understanding of low temperatures.

💡Perfect Crystal

A perfect crystal is a structure where all atoms are identical and positioned in perfectly symmetrical ways, as described in the script. It is in this state that entropy is minimized, according to the third law of thermodynamics. The concept of a perfect crystal is crucial for understanding the theoretical limits of entropy and the conditions under which absolute zero could theoretically be achieved.

💡James Dewar

James Dewar was a scientist who made significant contributions to low-temperature research, as mentioned in the script. He was the first to liquefy and then solidify hydrogen gas, reaching a temperature of 13 degrees above absolute zero. Dewar's work is historically significant as it represents an early milestone in the pursuit of achieving lower and lower temperatures, which is a central theme of the video.

💡Walther Nernst

Walther Nernst, a Prussian scientist, is noted in the script for formulating the heat theorem, which later became known as the third law of thermodynamics. Nernst's work is integral to the video's discussion on the theoretical understanding of low temperatures and the properties of matter at these extremes.

💡Dry Ice

Dry ice is solid carbon dioxide, which is created by solidifying CO2 into a snow-like consistency and then releasing pressure to cause it to vaporize and solidify. The script uses the process of making dry ice as an example of how the principles of thermodynamics can be applied in practical scenarios to achieve extreme cold temperatures, which is a key theme in the video's exploration of low-temperature physics.

💡Zeroth Law of Thermodynamics

The zeroth law of thermodynamics, while not explicitly detailed in the script, is implied in the discussion of temperature and its measurement. It states that if two systems are in thermal equilibrium with a third, they are in thermal equilibrium with each other. This law is foundational to the understanding of temperature and is relevant to the video's broader discussion on thermodynamics and temperature measurement.

Highlights

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

Temperatures in the Boomerang Nebula reach -272 degrees Celsius, just one degree above absolute zero.

Scientists have cooled molecules to 500 nano Kelvins using lasers, a temperature colder than the Boomerang Nebula.

Absolute zero, at 0 Kelvin, is a theoretical limit that cannot be experimentally achieved.

The third law of thermodynamics defines absolute zero and its relationship with entropy and temperature.

Entropy of a perfect crystal approaches zero at absolute zero, according to the third law of thermodynamics.

Absolute zero may not be achievable due to the second law of thermodynamics, which dictates heat transfer.

A perfect crystal with identical atoms in symmetrical positions is required for minimum entropy.

Imperfections in a crystal or residual thermal energy prevent entropy from reaching a minimum.

The inability to reach absolute zero implies that motion due to thermal energy will always exist.

James Dewar was the first to liquify and solidify hydrogen gas, reaching 13 degrees above absolute zero.

Walther Nernst's heat theorem, later known as the third law of thermodynamics, has practical applications in gas storage and usage.

Solidifying gases like carbon dioxide reduces their entropy and temperature, which can be exploited for cooling.

The third law of thermodynamics is a fundamental concept that helps explain the nature of heat and energy in our world.

The process of creating dry ice from carbon dioxide involves a rapid temperature drop and solidification.

The third law of thermodynamics, while seemingly simple, is crucial for understanding heat and energy phenomena.

Transcripts

The coldest place in the universe

is the Boomerang Nebula in the Centaurus constellation.

At -272 C, or 1 K,

it is only a single degree above absolute zero.

Here on Earth scientists have been able to get even colder than that

by using lasers to cool individual molecules of sodium and potassium

to 500 nano Kelvins.

But even they couldn't get to absolute zero.

The third law of thermodynamics defines what absolute zero is

and ties together the concepts of entropy and temperature.

It states that the entropy of a perfect crystal approaches zero

at a temperature of absolute zero.

An important idea to note is that absolute zero

may not be able to be achieved experimentally.

This is because we know from the second law of thermodynamics

that heat will spontaneously move from a warmer body to a cooler body.

So the object that you are trying to cool to absolute zero

will be taking in heat from its surroundings.

Despite this, absolute zero is an important theoretical concept.

The lowest possible entropy can only occur in a perfect crystal

which is a structure where all of the atoms that form it are identical

and positioned in perfectly symmetrical ways.

Any imperfections in the crystal carry an energy,

so the entropy won't be minimised.

Equally any residual thermal energy within the

crystal will create thermal motion within it

and again, your entropy won't be at a minimum.

Conversely that means that if we can't get to absolute zero,

then nothing in the universe is going to be completely still

as we'll always have some motion due to thermal energy.

One of the earliest forays into low temperature research was made by James Dewar

who was the first person who was able to liquify and then solidify hydrogen gas.

This reached a then record low temperature of 13 degrees above absolute zero

at which point he postulated: "there or thereabouts our progress is barred".

Nearly a decade later Prussian scientist Walther Nernst announced his heat theorem

which would later become known as the third law of thermodynamics.

This can be exploited when storing and using gases.

For example, carbon dioxide as a gas has a high entropy and a relatively high temperature.

We can reduce both by solidifying CO2 into a snow like consistency.

By releasing the pressure, some of the liquid carbon dioxide vaporises

and causes a rapid temperature drop and this extreme cold makes the substance

solidify.

I have made dry ice.

Similarly to the zeroth law, the third law of

thermodynamics may seem simple and obvious,

however it is the final piece of the puzzle which

helps us to explain our world

and the nature of its heat and energy.