13. Hukum Ketiga Termodinamika - Fisika N20

Summary

This video lesson explores the third law of thermodynamics, explaining key concepts like absolute zero (0 Kelvin), where atomic motion ceases, and entropy reaches its minimum value. It reviews the first two laws of thermodynamics and delves into how entropy increases with temperature and phase changes. The third law asserts that perfect crystals at absolute zero have zero entropy. The video also provides practical examples, highlighting why achieving absolute zero is impossible due to increasing entropy in real-world systems. Through engaging explanations, it reinforces the critical relationship between temperature, entropy, and kinetic energy in thermodynamic processes.

Takeaways

• 😀 The Zeroth Law of Thermodynamics defines thermal equilibrium: when two objects come into contact, they eventually reach the same temperature.
• 😀 The First Law of Thermodynamics is about the conservation of energy, where the change in energy is the sum of heat added and work done.
• 😀 The Second Law of Thermodynamics deals with entropy, stating that entropy (disorder) in a system always increases over time.
• 😀 The Third Law of Thermodynamics relates to absolute zero (0 Kelvin), where the entropy of a perfect crystal is zero and molecular movement stops.
• 😀 Absolute zero (0 Kelvin or -273.15°C) is the theoretical temperature at which all molecular motion ceases.
• 😀 Entropy increases with temperature; as temperature rises, molecules become more disordered, leading to higher entropy.
• 😀 At absolute zero, entropy is zero for a perfect crystal, as the particles are perfectly ordered and have no energy.
• 😀 Reaching absolute zero is practically impossible due to the fundamental thermodynamic limits imposed by increasing entropy in all processes.
• 😀 At absolute zero, all matter is in a solid phase, and particles have zero kinetic energy, meaning they stop moving entirely.
• 😀 The concept of entropy is crucial in understanding thermodynamic processes; it increases as energy is dispersed or when systems change phases (solid → liquid → gas).

Q & A

What is the third law of thermodynamics?

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. At absolute zero, molecular motion ceases, and energy reaches its lowest possible state.

How is absolute zero defined in terms of temperature?

Absolute zero is defined as 0 Kelvin, which is equivalent to -273.15°C. It is the lowest possible temperature where all molecular motion theoretically stops.

What happens to the entropy of a system as it reaches absolute zero?

As a system approaches absolute zero, its entropy decreases and approaches zero. At absolute zero, for a perfect crystal, the entropy is considered to be exactly zero.

Can absolute zero be reached in practice? Why or why not?

No, absolute zero cannot be reached in practice. According to the third law of thermodynamics, entropy always increases, making it impossible to achieve absolute zero.

What is the relationship between temperature and entropy?

Temperature and entropy are directly related. As the temperature of a system increases, its entropy also increases. This is evident from the behavior of substances transitioning through different phases (solid, liquid, gas) as temperature rises.

What does the first law of thermodynamics state?

The first law of thermodynamics is the law of energy conservation. It states that energy can neither be created nor destroyed, only transferred or converted from one form to another. The change in energy of a system is equal to the heat added to the system minus the work done by the system.

What is the zeroth law of thermodynamics about?

The zeroth law of thermodynamics defines thermal equilibrium. It states that if two bodies are each in thermal equilibrium with a third body, they are in thermal equilibrium with each other.

What happens to molecular motion at absolute zero?

At absolute zero, molecular motion completely stops. The particles are in their lowest possible energy state and do not move, leading to zero kinetic energy.

What are the three phases of matter discussed in relation to temperature and entropy?

The three phases of matter discussed are solid, liquid, and gas. As temperature increases, a substance transitions from solid to liquid, and then to gas, with entropy increasing at each phase transition.

What is the significance of perfect crystals at absolute zero?

At absolute zero, a perfect crystal is considered to have zero entropy because the atoms are arranged in a perfectly ordered and predictable structure. This is the theoretical ideal where no disorder or randomness exists.