📚 Key AP Chemistry Vocabulary Compilation (Part 2) | AP化学高频词汇汇编（中）
This second instalment of the AP Chemistry vocabulary series focuses on the core terms you will encounter in thermochemistry, kinetics, equilibrium, acid–base chemistry, thermodynamics, electrochemistry, nuclear chemistry, and common laboratory procedures. A firm grasp of these definitions is essential for interpreting free-response questions, analysing data, and writing precise explanations. Each entry is presented with a clear English definition followed by its Chinese equivalent to support bilingual learners.
这是AP化学词汇系列的第二部分，重点梳理热化学、动力学、化学平衡、酸碱化学、热力学、电化学、核化学以及常见实验操作中的高频术语。准确掌握这些定义对于解读自由问答题、分析实验数据和书写严谨的论证至关重要。每个条目都先给出英文释义，再提供对应的中文释义，以帮助双语学习者建立清晰的学科认知。
1. Thermochemistry and Calorimetry | 热化学与量热术语
Enthalpy (H) is a thermodynamic quantity equivalent to the internal energy of a system plus the product of its pressure and volume. In most AP problems, the change in enthalpy (ΔH) indicates whether a reaction releases or absorbs heat at constant pressure.
焓 (H) 是一个热力学状态函数，等于系统的内能加上压力与体积的乘积。在AP考试中，焓变 (ΔH) 通常用来表示恒压条件下反应是放热还是吸热。
Exothermic process: A reaction or physical change that releases heat to the surroundings, giving ΔH < 0. Typical examples include combustion and condensation.
放热过程： 向环境释放热量的反应或物理变化，ΔH 为负值。常见例子有燃烧和凝华（或冷凝）。
Endothermic process: A change that absorbs heat from the surroundings, so ΔH > 0. Photosynthesis and melting are endothermic.
吸热过程： 从环境吸收热量的变化，ΔH 为正值。光合作用和熔化都是吸热过程。
Specific heat capacity (c) is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius (or one kelvin). The equation q = mcΔT is central to calorimetry calculations.
比热容 (c) 是指将1克物质的温度升高1摄氏度（或1开尔文）所需的热量。公式 q = mcΔT 是量热计算的核心。
Calorimeter is a device used to measure heat changes during a reaction. A coffee-cup calorimeter works at constant pressure; a bomb calorimeter works at constant volume.
量热计 是用于测量反应过程中热量变化的装置。咖啡杯量热计在恒压下工作，而弹式量热计在恒容下工作。
Hess’s Law states that the overall enthalpy change for a reaction is equal to the sum of the enthalpy changes for the individual steps, regardless of the path taken.
盖斯定律 指出，一个反应的总焓变等于各分步反应的焓变之和，而与反应途径无关。
2. Chemical Kinetics | 化学动力学
Rate of reaction describes how quickly reactants are consumed or products are formed. It is usually expressed as a change in concentration per unit time, such as mol L⁻¹ s⁻¹.
反应速率 描述反应物消耗或产物生成的快慢，通常用单位时间内浓度的变化表示，单位为 mol L⁻¹ s⁻¹。
Activation energy (Ea) is the minimum energy that colliding particles must possess for a reaction to occur. On a potential-energy diagram, it is the energy barrier between reactants and the transition state.
活化能 (Ea) 是反应物粒子发生有效碰撞所必须具有的最低能量。在势能图中，它是反应物与过渡态之间的能垒。
Catalyst is a substance that increases the rate of a reaction by providing an alternative pathway with a lower activation energy, without being consumed itself.
催化剂 是一种通过提供更低活化能的替代路径来加快反应速率，而自身在反应前后保持不变的物质。
Rate law expresses the relationship between the reaction rate and the concentrations of reactants, each raised to a power (the order). For a reaction aA + bB → products, the rate law often takes the form rate = k[A]m[B]n.
速率方程 表达了反应速率与各反应物浓度之间的关系，各浓度项的指数即为反应级数。对于 aA + bB → 产物，速率方程通常具有 rate = k[A]m[B]n 的形式。
Reaction order with respect to a particular reactant is the exponent of its concentration term in the rate law. The overall order is the sum of the individual orders.
反应级数 指速率方程中某反应物浓度项的指数；总级数则是各分级数之和。
3. Chemical Equilibrium | 化学平衡
Dynamic equilibrium occurs when the forward and reverse reaction rates are equal, so the macroscopic concentrations of reactants and products remain constant while molecular-level changes continue.
动态平衡 表示正、逆反应速率相等，尽管微观粒子仍在不断变化，但宏观上各物质的浓度保持恒定。
Equilibrium constant (Kc, Kp) quantitatively describes the ratio of product concentrations to reactant concentrations at equilibrium, each raised to the power of its stoichiometric coefficient. Kc uses molar concentrations; Kp uses partial pressures.
平衡常数 (Kc, Kp) 定量描述平衡时产物浓度（或分压）幂的乘积与反应物浓度幂的乘积之比。Kc 基于物质的量浓度，Kp 基于气体分压。
Le Châtelier’s Principle predicts that if a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium will shift to partially counteract that disturbance.
勒夏特列原理 指出，处于平衡的体系若受到浓度、温度或压力的扰动，平衡会向削弱该扰动影响的方向移动。
Reaction quotient (Q) has the same mathematical form as the equilibrium constant, but uses concentrations (or pressures) at any point in time, not necessarily at equilibrium. Comparing Q and K tells us which direction the reaction must shift to reach equilibrium.
反应商 (Q) 的数学表达式与平衡常数相同，但代入的是任意时刻的浓度或分压。通过比较 Q 与 K，可以判断反应必须向哪个方向移动才能达到平衡。
4. Acids, Bases, and pH | 酸、碱与pH值
Arrhenius definition: Acids produce H⁺ ions in aqueous solution; bases produce OH⁻ ions.
阿伦尼乌斯定义： 酸在水溶液中产生 H⁺ 离子，碱产生 OH⁻ 离子。
Brønsted-Lowry definition: Acids are proton (H⁺) donors; bases are proton acceptors. This definition expands acid–base chemistry to non-aqueous systems.
布朗斯特-劳里定义： 酸是质子 (H⁺) 的给予体，碱是质子的接受体。该定义将酸碱概念拓展到了非水体系。
Conjugate acid–base pair consists of two species that differ by a single proton. For example, CH₃COOH (acid) and CH₃COO⁻ (its conjugate base).
共轭酸碱对 由一对仅相差一个质子的物质组成，例如 CH₃COOH（酸）与 CH₃COO⁻（其共轭碱）。
pH and pOH: pH = –log[H⁺], pOH = –log[OH⁻], and pH + pOH = 14.00 at 25 °C. These logarithmic scales make it easier to handle the wide range of ion concentrations.
pH 与 pOH： pH = –log[H⁺]，pOH = –log[OH⁻]，且在 25 °C 时 pH + pOH = 14.00。这些对数尺度便于处理跨度极大的离子浓度。
Strong vs weak acids: A strong acid completely dissociates in water (e.g. HCl), whereas a weak acid only partially dissociates, establishing an equilibrium (e.g. CH₃COOH).
强酸与弱酸的区别： 强酸在水中完全解离（如 HCl），而弱酸仅部分解离，建立解离平衡（如 CH₃COOH）。
5. Buffer Solutions and Titrations | 缓冲溶液与滴定
Buffer solution resists significant changes in pH upon the addition of small amounts of strong acid or base. It typically contains a weak acid and its conjugate base (or a weak base and its conjugate acid) in similar concentrations.
缓冲溶液 能在加入少量强酸或强碱时抵御 pH 的剧烈变化，通常由浓度相近的弱酸及其共轭碱（或弱碱及其共轭酸）组成。
Henderson-Hasselbalch equation relates pH, pKa, and the ratio of conjugate base to acid: pH = pKa + log([A⁻]/[HA]). It is valid only when the approximations of the equilibrium system hold.
亨德森-哈塞尔巴尔赫方程 关联了 pH、pKa 与共轭碱浓度和酸浓度之比：pH = pKa + log([A⁻]/[HA])。该方程只有在体系近似条件成立时才适用。
Equivalence point in a titration is the point at which stoichiometrically equivalent amounts of acid and base have been mixed. The pH at the equivalence point depends on the strengths of the acid and base.
等当点 是滴定中酸与碱恰好按化学计量比完全反应的时刻；等当点的 pH 取决于参与反应的酸和碱的强弱。
End point is the point at which the indicator changes colour, which ideally should be close to the equivalence point.
滴定终点 是指示剂发生颜色变化的时刻，理想情况下应尽可能接近等当点。
Titration curve is a graph of pH versus volume of titrant added. The shape reveals information about the acid or base strength and the buffer region.
滴定曲线 是以 pH 对加入的滴定剂体积作图所得曲线，其形状能反映酸碱强度以及缓冲区域的信息。
6. Solubility Equilibria and Ksp | 溶解平衡与溶度积
Solubility product constant (Ksp) is the equilibrium constant for a sparingly soluble ionic compound dissolving in water. For AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), Ksp = [Ag⁺][Cl⁻].
溶度积常数 (Ksp) 是微溶离子化合物在水中溶解的平衡常数。对于 AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq)，Ksp = [Ag⁺][Cl⁻]。
Molar solubility is the number of moles of a solute that dissolve to form one litre of a saturated solution. It can be calculated from Ksp using the stoichiometry of the dissolution reaction.
摩尔溶解度 是溶质在形成1升饱和溶液时所溶解的物质的量（摩尔），可通过 Ksp 和溶解反应的计量关系进行计算。
Common ion effect describes the decrease in solubility of a salt when a soluble compound that shares a common ion is added. It is a direct consequence of Le Châtelier’s Principle.
同离子效应 指向溶解平衡中加入含相同离子的可溶化合物时，沉淀的溶解度降低的现象，这是勒夏特列原理的直接应用。
Precipitation occurs when the ion product (Q) exceeds Ksp, indicating that the solution is supersaturated and a solid will form until Q equals Ksp.
沉淀 当离子积 (Q) 大于 Ksp 时即会发生，表明溶液呈过饱和状态，固体会不断析出直至 Q 等于 Ksp 为止。
7. Thermodynamics: Entropy and Gibbs Free Energy | 热力学：熵与吉布斯自由能
Entropy (S) is a measure of the disorder or randomness of a system. The second law of thermodynamics states that the total entropy of the universe always increases in a spontaneous process.
熵 (S) 是系统混乱度或随机性的量度。热力学第二定律指出，在一个自发过程中，宇宙的总熵始终增加。
Gibbs free energy (G) combines enthalpy and entropy to predict spontaneity: ΔG = ΔH – TΔS. A negative ΔG indicates a thermodynamically spontaneous process under constant temperature and pressure.
吉布斯自由能 (G) 结合了焓与熵，用以判断自发过程的方向：ΔG = ΔH – TΔS。在恒温恒压下，ΔG 为负表明过程是热力学自发的。
Standard free-energy change (ΔG°) is the free-energy change when all reactants and products are in their standard states. It is related to the equilibrium constant by: ΔG° = –RT ln K.
标准自由能变 (ΔG°) 是指所有反应物和产物均处于标准态时的自由能变化，它与平衡常数之间的关系为：ΔG° = –RT ln K。
Spontaneous process is one that occurs without continuous external intervention. Spontaneity is determined by the sign of ΔG, not by the speed of the reaction.
自发过程 指无需持续外部干预即可发生的过程。自发性由 ΔG 的正负符号决定，而与反应快慢无关。
8. Electrochemistry and Cell Potentials | 电化学与电池电势
Oxidation is the loss of electrons (increase in oxidation state). Reduction is the gain of electrons (decrease in oxidation state). Together they form redox reactions.
氧化 是失去电子（氧化态升高）的过程；还原 是得到电子（氧化态降低）的过程，两者共同构成氧化还原反应。
Galvanic (voltaic) cell uses a spontaneous redox reaction to generate an electric current. The oxidation half-reaction occurs at the anode, and the reduction half-reaction occurs at the cathode.
原电池（伏打电池） 利用自发的氧化还原反应产生电流，氧化半反应发生在阳极，还原半反应发生在阴极。
Electrolytic cell uses an external power source to drive a non-spontaneous redox reaction. Here the anode is positive and the cathode is negative, opposite to a galvanic cell.
电解池 利用外部电源驱动非自发的氧化还原反应，其中阳极为正极，阴极为负极，与原电池正负极恰好相反。
Standard reduction potential (E°) measures the tendency of a half-cell to gain electrons under standard conditions. The cell potential E°cell = E°cathode – E°anode.
标准还原电势 (E°) 衡量半电池在标准条件下获得电子的倾向。电池电动势 E°cell = E°cathode – E°anode.
Nernst equation adjusts the cell potential for non-standard concentrations: E = E° – (RT/nF) ln Q. At 298 K, it simplifies to E = E° – (0.0592/n) log Q.
能斯特方程 修正了非标准浓度下的电池电动势：E = E° – (RT/nF) ln Q。在 298 K 时可简化为 E = E° – (0.0592/n) log Q。
9. Nuclear Chemistry Essentials | 核化学精要
Radioactive decay is the spontaneous disintegration of an unstable nucleus with the emission of particles or electromagnetic radiation. Common modes include alpha (α), beta (β), and gamma (γ) decay.
放射性衰变 是不稳定原子核自发分裂，并放射出粒子或电磁辐射的过程。常见衰变方式有 α 衰变、β 衰变和 γ 衰变。
Alpha particle (α) is a helium-4 nucleus (⁴₂He). Beta-minus particle (β⁻) is a high-energy electron. Gamma ray (γ) is high-frequency electromagnetic radiation with no mass or charge.
α 粒子 是氦-4 核 (⁴₂He)；β⁻ 粒子是高速电子；γ 射线是高频电磁波，无静止质量、不带电荷。
Half-life (t½) is the time required for half of a radioactive sample to decay. It is a constant for a given isotope and is used in radiometric dating and nuclear medicine.
半衰期 (t½) 是指放射性样品中一半原子核发生衰变所需的时间，对于给定同位素是常数，广泛应用于放射性定年和核医学。
Nuclear fission is the splitting of a heavy nucleus into lighter nuclei, releasing a large amount of energy. Nuclear fusion combines light nuclei to form a heavier one, the process that powers the Sun.
核裂变 是重核分裂为轻核并释放巨大能量的过程；核聚变 则是轻核结合成较重核的过程，是太阳的能量来源。
10. Key Laboratory Terms | 基本实验术语
Meniscus is the curved surface of a liquid column inside a graduated cylinder or burette. For aqueous solutions, the bottom of the meniscus is read at eye level to ensure accurate volume measurement.
弯月面 是指量筒或滴定管中液柱的弯曲液面。对于水溶液，读数时应视线与弯月面最低点水平，以确保体积测量准确。
Burette is a long, precisely graduated glass tube with a stopcock, used to deliver variable, measured volumes of a liquid, especially in titrations.
滴定管 是一根带有旋塞的长刻度玻璃管，用于在滴定等实验中精确放出可变体积的液体。
Pipette is a calibrated glass tube used to transfer a fixed, accurate volume of liquid. A volumetric pipette delivers a single volume, while a graduated pipette can deliver multiple volumes.
移液管 是校准过的玻璃管，用于准确移取一定体积的液体；单标移液管移取固定体积，刻度移液管可移取多个不同体积。
Titration is an analytical technique where a solution of known concentration (titrant) is added to a solution of unknown concentration until the reaction is complete, enabling determination of the unknown concentration.
滴定 是一种将已知浓度的溶液（滴定剂）逐滴加入未知浓度溶液中直至反应完全的分析技术，据此可求得未知溶液的浓度。
Supernatant refers to the clear liquid lying above a solid residue after precipitation or centrifugation. Decanting carefully separates the supernatant from the precipitate.
上清液 指沉淀或离心后位于固体残渣上方的澄清液体，可通过小心倾析将其与沉淀分离。
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