📚 Entropy and Temperature | 熵与温度
Entropy is a central concept in A-Level Chemistry that describes the dispersal of energy and the degree of disorder in a chemical system. Temperature is not just a measure of hotness; it determines how far that dispersed energy can drive a reaction towards equilibrium.
熵是 A-Level 化学中的一个核心概念，用于描述化学体系中能量的分散程度和无序程度。温度不仅是冷热的量度，还决定了分散的能量能在多大程度上推动反应向平衡方向进行。
1. What Is Entropy? | 什么是熵？
Entropy, symbol S, is a thermodynamic state function that measures the number of ways energy can be distributed among the particles in a system. A system with more possible arrangements of energy has higher entropy.
熵（符号为 S）是一个热力学状态函数，用于量度能量在体系中粒子之间可能分布方式的数量。能量排列方式越多的体系，其熵值越高。
In simple terms, entropy is often described as a measure of disorder. A gas has higher entropy than a liquid of the same substance, and a liquid has higher entropy than a solid because particles are more randomly arranged.
简单来说，熵常被描述为无序程度的量度。同一物质的气态比液态熵值高，液态比固态熵值高，因为粒子的排列更加混乱。
2. Units and Standard Entropy Values | 单位与标准熵值
Entropy is measured in joules per kelvin per mole, J K⁻¹ mol⁻¹. Standard molar entropy, S°, is the entropy of one mole of a substance under standard conditions, usually 298 K and 100 kPa.
熵的单位是焦耳每开尔文每摩尔（J K⁻¹ mol⁻¹）。标准摩尔熵（S°）是一摩尔物质在标准条件下（通常为 298 K 和 100 kPa）的熵值。
Unlike enthalpy, standard entropy values are absolute values. There is no need to define an arbitrary zero because the third law of thermodynamics states that a perfect crystal at 0 K has zero entropy.
与焓不同，标准熵值是绝对值。无需人为定义零点，因为热力学第三定律指出：完美晶体在 0 K 时的熵为零。
3. Entropy and Physical State | 熵与物态
Entropy increases in the order solid < liquid < gas. Melting and boiling therefore have positive entropy changes because particles gain freedom of movement.
熵按固态 < 液态 < 气态的顺序增大。因此熔化和沸腾过程的熵变为正值，因为粒子获得了更大的运动自由度。
Dissolving an ionic solid usually increases entropy because a regular lattice breaks into mobile ions in solution, although some solvent ordering around ions can reduce the increase.
离子固体溶解通常会使熵增大，因为规则晶格解体为溶液中可移动的离子，尽管离子周围溶剂的有序化会在一定程度上减小这一增幅。
a reaction also raises entropy. For example, N₂O₄(g) → 2NO₂(g) has a positive ΔS(system).
反应中气体分子数的增加也会使熵增大。例如 N₂O₄(g) → 2NO₂(g) 的体系熵变 ΔS(system) 为正值。
4. Temperature and Kinetic Energy | 温度与动能
Temperature is a measure of the average kinetic energy of particles. At higher temperatures, particles move faster, occupy more energy levels, and create more possible energy distributions.
温度是粒子平均动能的量度。温度越高，粒子运动越快，占据的能级越多，可能的能量分布方式也越多。
This means the entropy of a substance increases with temperature,
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