什么是配位键？
What is a coordinate bond?
配位键是一种特殊的共价键，成键的一对电子完全由同一个原子（配体）提供，另一原子提供空轨道接受。它常见于配合物和铵离子（NH4+）中。配位键形成后与其他共价键在性质上没有本质区别。
A coordinate bond is a special covalent bond in which both electrons of the shared pair are donated entirely by one atom (the ligand) while the other supplies an empty orbital. It is common in complexes and the ammonium ion (NH4+). Once formed, it is essentially no different from other covalent bonds.
难度 专业 · 适合 高中(15-18)
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Housecroft 与 Sharpe《无机化学》（第5版，Pearson）配位键（dative bond）章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (coordinate/dative bonds)
#配位键 #孤对电子 #配合物
什么是螯合作用？
What is chelation?
螯合是多齿配体通过两个或更多配位原子与同一中心金属离子形成环状结构的配位方式，生成的配合物称为螯合物。由于环状结构稳定（螯合效应），螯合物通常比单齿配合物更难解离。EDTA是常见的强螯合剂，用于净水与解毒。
Chelation is when a polydentate ligand binds the same central metal ion through two or more donor atoms, forming a ring-like complex called a chelate. Thanks to ring stability (the chelate effect), chelates are usually harder to dissociate than monodentate complexes. EDTA is a common strong chelator used in water treatment and detoxification.
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Housecroft 与 Sharpe《无机化学》（第5版，Pearson）螯合效应章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (chelate effect)
#螯合 #多齿配体 #EDTA
什么是杂化轨道？
What are hybrid orbitals?
杂化轨道理论把中心原子能量相近的原子轨道线性组合成数目相等、方向更利于成键的新轨道，如sp、sp2、sp3杂化。它解释了分子的几何构型与键角。杂化不改变电子总数，只重新分配空间取向。
Hybrid orbital theory linearly combines atomic orbitals of similar energy on a central atom into the same number of new orbitals better oriented for bonding, such as sp, sp2 and sp3 hybridization. It explains molecular geometry and bond angles. Hybridization keeps the total electron count and only redistributes spatial orientation.
难度 专业 · 适合 高中(15-18)
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Brown、LeMay、Bursten 等《化学：中心科学》（第14版，Pearson）杂化轨道理论章节
Brown, T. L.; LeMay, H. E.; Bursten, B. E.; et al. Chemistry: The Central Science, 14th ed., Pearson (hybrid orbital theory)
独立核验依据 · Independent verification: 核验依据 1 ARCHIVE 标识 studentlectureno00theo：Chemistry, the central
#杂化轨道 #sp3 #分子构型
什么是手性分子？
What is a chiral molecule?
手性分子是指与其镜像不能重合的分子，如同左手与右手。通常分子中存在一个连有四个不同基团的碳原子（手性中心）时即具有手性。手性分子常成对出现为对映异构体，其旋光性和生物活性可能完全不同。
A chiral molecule is one that cannot be superimposed on its mirror image, like a left and right hand. Chirality usually arises when a carbon atom is bonded to four different groups (a chiral center). Chiral molecules commonly appear as enantiomers whose optical activity and biological behavior can differ completely.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
McMurry, J. 《有机化学》（第9版，Cengage）立体化学与手性章节
McMurry, J. Organic Chemistry, 9th ed., Cengage (stereochemistry; chirality)
#手性 #对映异构 #旋光性
超临界二氧化碳为什么常被用作绿色溶剂？
Why is supercritical CO2 widely used as a green solvent?
当温度和压强超过二氧化碳的临界点（31.1摄氏度、7.38兆帕）时，CO2进入超临界态：密度接近液体，而黏度和扩散系数接近气体，溶解能力可通过温度和压强连续调节，能溶解多种非极性物质。反应或萃取后减压即可让CO2气化分离，无溶剂残留，因此广泛用于咖啡因萃取、天然产物提取和绿色清洗。
Beyond the critical point of CO2 (31.1 degrees Celsius, 7.38 MPa), the fluid becomes supercritical: density near that of a liquid while viscosity and diffusivity approach those of a gas, with solvating power tunable continuously by temperature and pressure and able to dissolve many nonpolar substances. Releasing pressure vaporizes the CO2 with no solvent residue, so it is used for caffeine decaffeination, natural-product extraction and green cleaning.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-03
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《无机化学》相平衡章节
Inorganic Chemistry (phase equilibrium); IUPAC (supercritical fluid)
#超临界流体 #相图 #绿色溶剂
为什么有的四配位配合物是四面体形，有的是平面正方形？
Why are some four-coordinate complexes tetrahedral while others are square planar?
中心离子的d电子数和配体场共同决定几何构型。d8构型的Pt2+、Au3+以及强场下的Ni2+等常形成平面正方形，因为此时晶体场稳定化能最高，顺铂是典型代表；而大多数d0到d5离子以及弱场下的高自旋d7到d10离子（如[CoCl4]2-（d7）、Zn2+（d10））则倾向于四面体。配体体积大时也因空间排斥而偏好四面体。
The d-electron count of the central ion and the ligand field together set the geometry. d8 ions such as Pt2+ and Au3+, and Ni2+ in strong fields, often form square-planar complexes because crystal-field stabilization energy is greatest there; cisplatin is the classic example. Most d0-d5 ions, and high-spin d7-d10 ions in weak fields such as [CoCl4]2- (d7) and Zn2+ (d10), prefer tetrahedral geometry, and bulky ligands also favor tetrahedral to reduce steric repulsion.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-03
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《无机化学》配位化学章节
Inorganic Chemistry (coordination chemistry); IUPAC (coordination nomenclature)
#配位几何 #晶体场理论 #顺铂
为什么半导体（如硅）的导电性随温度升高而增强，而金属却相反？
Why does a semiconductor's conductivity increase as temperature rises, while a metal's does the opposite?
金属的导带已充满可动电子，升温只加剧晶格振动（散射），使电阻增大、导电性下降。半导体在接近绝对零度时价带满、导带空，升温把电子激发越过禁带进入导带，载流子数量指数增加，导电性随之增强。
Metals already have a filled band of mobile electrons, so heating mainly increases lattice scattering, raising resistance and lowering conductivity. A semiconductor's valence band is full and conduction band empty near 0 K; heating excites electrons across the band gap, exponentially increasing carriers and thus conductivity.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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Atkins & de Paula《物理化学》（第10版），第21章固体电子
Atkins & de Paula, "Physical Chemistry" (10th ed.), Ch.21
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1907523W：Physical chemistry（首版 1
#半导体 #能带理论 #禁带 #金属导电
什么是芳香性？
What is aromaticity?
芳香性指环状、平面且含有4n+2个离域π电子（休克尔规则）的分子所表现出的异常稳定性。苯是最典型的芳香化合物，其π电子离域使键长均等、不易发生加成而倾向取代。芳香性显著影响其化学行为与光谱。
Aromaticity is the exceptional stability shown by cyclic, planar molecules with 4n+2 delocalized pi electrons (Hückel's rule). Benzene is the classic aromatic compound; its delocalized pi electrons equalize bond lengths and favor substitution over addition. Aromaticity strongly influences chemical behavior and spectra.
难度 专业 · 适合 大众
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
McMurry, J. 《有机化学》（第9版，Cengage）芳香性与休克尔规则章节
McMurry, J. Organic Chemistry, 9th ed., Cengage (aromaticity; Hückel's rule)
#芳香性 #苯 #休克尔规则
什么是共振结构？
What are resonance structures?
共振结构指同一分子可用多种路易斯结构来表示，实际分子是这些结构的杂化体，没有一个单独结构能完整描述。例如碳酸根的三个C-O键等长，是三种共振式的平均。共振降低了分子能量，使其更稳定。
Resonance structures are multiple Lewis representations of the same molecule; the real molecule is a hybrid of them, and no single structure fully describes it. For example, the three C-O bonds in carbonate are equal in length, the average of three resonance forms. Resonance lowers the molecule's energy and stabilizes it.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
McMurry, J. 《有机化学》（第9版，Cengage）共振结构章节
McMurry, J. Organic Chemistry, 9th ed., Cengage (resonance structures)
#共振 #路易斯结构 #杂化
EDTA为什么能与多种金属离子配位？螯合效应如何解释？
Why does EDTA coordinate with many metal ions, and how is the chelate effect explained?
EDTA含两个氨基和四个羧基，共六个配位原子，能与金属离子形成1比1的六齿螯合物。螯合效应的热力学根源主要是熵增：配体结合时释放出多个原先独立结合的水分子，体系混乱度增大，使吉布斯自由能变化更负，配合物因而更稳定。这也是EDTA用于水软化、重金属解毒和定量分析的原因。
EDTA has two amino and four carboxyl groups - six donor atoms - and forms 1:1 hexadentate chelates with metal ions. The chelate effect is largely entropic: binding releases several water molecules that were independently coordinated, increasing the disorder of the system, making the Gibbs free energy change more negative and the complex more stable. This is why EDTA softens water, treats heavy-metal toxicity and serves in quantitative analysis.
难度 专业 · 适合 高中(15-18)
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《无机化学》配位化合物章节
Inorganic Chemistry (coordination compounds); IUPAC (chelate effect)
#螯合效应 #熵增 #EDTA
为什么液氮能用于冷冻？
Why can liquid nitrogen be used for freezing?
液氮在标准大气压下沸点约为零下196摄氏度，气化时吸收大量热且本身化学性质极其稳定、不助燃。因此它能快速带走热量实现深度冷冻，广泛用于生物样本保存和食品速冻。
Liquid nitrogen boils at about minus 196 degrees Celsius at standard pressure and absorbs large amounts of heat as it vaporizes, while being chemically inert and non-flammable. It therefore rapidly removes heat for deep freezing, used in preserving biological samples and quick-freezing food.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#液氮 #低温 #冷冻
为什么食盐晶体呈立方体？
Why do table salt crystals form cubes?
氯化钠中钠离子与氯离子按1:1交替排列成立方最密堆积的晶格，空间结构本身具有立方对称性。在自由生长且环境均匀时，晶面按对称方式发育，宏观上就呈现立方体外形。晶体的外形是内部点阵结构的反映。
In sodium chloride, sodium and chloride ions alternate 1:1 in a cubic closest-packed lattice with inherent cubic symmetry. Growing freely in a uniform environment, the crystal faces develop symmetrically and appear cubic macroscopically. A crystal's shape reflects its internal lattice structure.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Housecroft 与 Sharpe《无机化学》（第5版，Pearson）离子晶体（氯化钠）章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (ionic crystals; sodium chloride structure)
#食盐 #晶体 #立方
什么是饱和溶液？如何判断一杯溶液是否饱和？
What is a saturated solution, and how can you tell whether a solution is saturated?
在给定温度和压强下，当溶质溶解的速率与从溶液中结晶析出的速率相等时，溶液达到饱和，此时的浓度就是该条件下的溶解度。判断办法：再投入一些溶质不再溶解，或者晃动时已有晶体始终不消失，通常就说明溶液已饱和。
At a given temperature and pressure, a solution is saturated when solute dissolves at the same rate as it crystallizes back out; that concentration is the solubility under those conditions. To test it, add a little more solute and see whether it refuses to dissolve, or check whether existing crystals never disappear when shaken - both indicate saturation.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#饱和溶液 #溶解度 #动态平衡
金属通常都是固体，为什么汞在常温下却是唯一的液态金属？
Metals are usually solid at room temperature - why is mercury the only liquid metal under normal conditions?
金属的熔点与原子间金属键的强弱有关。汞的6s电子被相对论效应锁紧在原子核附近，6s轨道收缩、能量降低，难以参与金属键的形成，汞原子之间只能形成很弱的结合，因此熔点只有零下39摄氏度，常温下呈液态。这种相对论效应还让金呈现金黄色。汞虽然漂亮，但常温下会缓慢挥发，其蒸气有毒，含汞体温计打碎后要及时通风处理。
A metal's melting point reflects the strength of its metallic bonding. In mercury, relativistic effects pull the 6s electrons close to the nucleus, shrinking and stabilizing that orbital so it barely takes part in metallic bonding; the weak bonds between mercury atoms give it a melting point of only -39 °C, so it is a liquid at room temperature. The same relativistic effects tint gold yellow. Mercury looks pretty, but it evaporates slowly even at room temperature and its vapour is toxic, so a broken mercury thermometer must be ventilated and cleaned up promptly.
难度 进阶 · 适合 大众
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出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
《普通化学》（元素周期表）
General Chemistry (periodic table)
#汞 #液态金属 #相对论效应
什么是配位化合物？
What is a coordination compound?
配位化合物由中心原子（常为金属离子）与围绕它的若干配体通过配位键结合而成。配体提供孤对电子，中心原子提供空轨道接受电子。配合物广泛存在于生物（如血红素）和工业催化中。
A coordination compound consists of a central atom (often a metal ion) surrounded by ligands bonded through coordinate bonds. The ligand donates a lone pair and the central atom provides empty orbitals to accept it. Complexes are widespread in biology (e.g. heme) and industrial catalysis.
难度 进阶 · 适合 大众
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Housecroft 与 Sharpe《无机化学》（第5版，Pearson）配位化学章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (coordination chemistry)
#配合物 #配位键 #配体
煮汤时加盐，为什么水的沸点会略微升高？
Why does adding salt slightly raise the boiling point of cooking water?
这属于依数性中的沸点升高。加入不挥发的溶质后，溶液的蒸气压比纯水低，必须加热到更高温度才能让蒸气压等于外界大气压而沸腾。沸点升高量只取决于溶质的质量摩尔浓度，与溶质种类无关。日常烹饪加盐量少，升高幅度很小，主要作用是调味。
This is boiling-point elevation, a colligative property. A nonvolatile solute lowers the vapor pressure, so the solution must be heated to a higher temperature before its vapor pressure matches the external pressure. The elevation depends only on the molality, not on what the solute is. In everyday cooking the salt amount is small, so the effect is slight and mostly for flavor.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#依数性 #沸点升高 #蒸气压
同一种物质为什么会形成不同的晶体形态（多晶型）？这为什么对药物特别重要？
Why can the same substance form different crystal shapes (polymorphism), and why does this matter for medicines?
多晶型指同一化学组成因分子排列或构象不同而形成多种晶型，各晶型的稳定性、熔点和溶解度都不同。药物的不同晶型溶出速率可能差很多，直接影响药效与安全性，因此药典对关键药物的晶型有严格规定。
Polymorphism is when one composition adopts several crystal forms differing in molecular packing or conformation, each with distinct stability, melting point, and solubility. Different polymorphs of a drug can dissolve at very different rates, directly affecting efficacy and safety, so pharmacopeias strictly control crystal forms of key medicines.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Bernstein《多晶型：分子晶体的稳定形式》（Polymorphism in Molecular Crystals）
Bernstein, "Polymorphism in Molecular Crystals" (Cambridge Univ. Press)
#多晶型 #晶型 #药物 #溶解度
什么是键能？
What is bond energy?
键能指气态下断开1摩尔某化学键所需的能量，或形成该键释放的能量，通常取平均值。键能越大，化学键越牢固、分子越稳定。比较不同分子的键能有助于判断反应放热还是吸热。
Bond energy is the energy needed to break one mole of a given bond in the gas phase, or released when it forms, usually taken as an average. The larger the bond energy, the stronger the bond and the more stable the molecule. Comparing bond energies helps judge whether a reaction is exothermic or endothermic.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#键能 #化学键 #稳定性
SF₆ 中硫原子采用什么杂化方式？分子几何是什么？
What hybridization does sulfur use in SF₆, and what is its molecular geometry?
硫采用 sp³d² 杂化，由 6 对成键电子形成八面体构型，键角均为 90° 和 180°。六氟化硫因对称且无可极化的孤对电子而化学惰性强。
Sulfur uses sp³d² hybridization, forming an octahedral geometry with 90° and 180° bond angles from six bonding pairs. SF₆ is chemically inert due to its symmetric, non-polarizable structure.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
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大连理工大学无机化学教研室 编,《无机化学》第6版,高等教育出版社
Dalian University of Technology Inorganic Chemistry Group, Inorganic Chemistry, 6th ed., Higher Education Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040492750（豆瓣书目条目: 无机化学）
#杂化 #分子几何 #价层电子
为什么牛奶是白色浑浊的乳液，而不是清亮的液体？
Why does milk look like a white turbid emulsion rather than a clear liquid?
牛奶是胶体，属于水包油型乳浊液：酪蛋白等包裹着微小的脂肪球分散在水中，粒子直径约0.1到10微米，与可见光波长相当，对光产生强烈散射，所以整体呈白色。若均质化不充分，脂肪球会上浮分层，这就是放置后出现奶油层的原因。
Milk is a colloid, specifically an oil-in-water emulsion: casein coats tiny fat globules dispersed in water, forming particles about 0.1 to 10 micrometers across. Being comparable to visible wavelengths, these particles scatter light strongly, so the milk looks white. If homogenization is incomplete, the globules rise and cream separates on top.
难度 进阶 · 适合 初中(12-15)
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《普通化学》(Atkins) 胶体章节
General Chemistry (Atkins), colloids; Royal Society of Chemistry
#胶体 #乳浊液 #光散射
金刚石和石墨都由碳原子组成，为什么一个硬得能划玻璃，另一个软得能写字？
Diamond and graphite are both made of carbon atoms, so why is one hard enough to cut glass while the other is soft enough to write?
差别在于碳原子的连接方式。金刚石中每个碳以四个共价键与相邻碳形成三维网状结构，四面体骨架非常坚固，所以最硬；石墨中碳在平面内以三个键连成六角形层片，层与层之间只靠微弱的范德华力结合，容易滑动，因此又软又能导电。这两种由同种元素形成的不同单质叫同素异形体，碳纳米管、石墨烯也是碳的其他形态。
It all comes down to how the carbon atoms are linked. In diamond each carbon forms four covalent bonds in a three-dimensional tetrahedral network that is extremely rigid, making it the hardest natural material; in graphite each carbon bonds to three neighbours in flat hexagonal sheets, and the sheets are held together only by weak van der Waals forces, so they slide easily - graphite is soft, and the mobile electrons make it conductive. Different forms of the same element are allotropes; carbon nanotubes and graphene are further members of carbon's family.
难度 进阶 · 适合 大众
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出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
《普通化学》（同素异形体）
General Chemistry (allotropy)
#同素异形体 #金刚石 #石墨
为什么一束光穿过胶体能看见光路，穿过真溶液却看不见？
Why does a light beam leave a visible path in a colloid but not in a true solution?
这是丁达尔效应。胶体粒子直径在1到1000纳米之间，尺寸接近可见光波长，对光产生明显散射，使光束在胶体中显出光路；真溶液中溶质是分子或离子，远小于波长，散射极弱，光路不可见。因此丁达尔效应常用来区分胶体和真溶液。
This is the Tyndall effect. Colloid particles, 1 to 1000 nanometers across, are close to the wavelength of visible light and scatter it strongly, leaving a visible beam path; true solutions contain molecules or ions far smaller than the wavelength, so scattering is negligible and no path appears. The Tyndall effect is thus a quick test for distinguishing a colloid from a true solution.
难度 进阶 · 适合 大众
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《普通化学》(Atkins) 胶体章节
General Chemistry (Atkins), colloids; Encyclopaedia Britannica (Tyndall effect)
#丁达尔效应 #胶体 #散射
为什么天气炎热时鱼塘里的鱼容易缺氧？
Why do fish in ponds easily run short of oxygen in hot weather?
气体在水中的溶解度随温度升高而降低。溶解是放热过程，升温使溶解平衡向气体逸出方向移动，热天水中溶氧明显减少；加上微生物活动加剧、耗氧加快，鱼更容易浮头缺氧。冷水中溶氧量高，这就是夏天要给鱼缸降温增氧的原因。
Gas solubility in water falls as temperature rises. Dissolution is exothermic, so warming shifts the equilibrium toward gas escaping; hot water therefore holds much less dissolved oxygen. With microbial activity also consuming oxygen faster, fish are more likely to gasp at the surface. Cold water holds more oxygen, which is why aquariums are cooled and aerated in summer.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#溶解度 #气体 #温度
稀有气体化合物是否存在？
Do compounds of noble gases exist?
虽然稀有气体极不活泼，但较重的氪、氙、氡能与强电负性的氟、氧形成化合物，如六氟化氙（XeF6）。最轻的氦和氖至今几乎未形成稳定化合物。稀有气体化合物的合成打破了惰性的传统观念。
Although noble gases are very unreactive, the heavier krypton, xenon and radon can form compounds with highly electronegative fluorine or oxygen, such as xenon hexafluoride (XeF6). The lightest, helium and neon, have almost no stable compounds known. Their synthesis overturned the traditional idea of inertness.
难度 进阶 · 适合 大众
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出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
Housecroft 与 Sharpe《无机化学》（第5版，Pearson）稀有气体化合物章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (noble-gas compounds)
#稀有气体化合物 #氙 #氟化
晶体里的"配位数"是什么意思？为什么 NaCl 是 6 配位而 CsCl 是 8 配位？
What does "coordination number" mean in a crystal, and why is NaCl 6-coordinate while CsCl is 8-coordinate?
配位数指一个离子（或原子）周围最近邻、等距的异号离子（或原子）的数目。NaCl 中每个 Na⁺ 被 6 个 Cl⁻ 包围（6:6），对应面心立方堆积；CsCl 的离子半径比更大，每个 Cs⁺ 可容纳 8 个 Cl⁻（8:8），呈简单立方结构。
Coordination number is the count of nearest equidistant oppositely charged ions (or atoms) around a given ion. In NaCl each Na⁺ is surrounded by six Cl⁻ (6:6) in a face-centered cubic arrangement; CsCl's larger radius ratio lets each Cs⁺ fit eight Cl⁻ (8:8) in a simple cubic structure.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Housecroft & Sharpe,《Inorganic Chemistry》第5版,Pearson,2018
C. E. Housecroft and A. G. Sharpe, Inorganic Chemistry, 5th ed., Pearson, 2018
#配位数 #晶体结构 #NaCl #CsCl
为什么冰会浮在水面上？这与水分子的什么结构有关？
Why does ice float on liquid water, and which structural feature is responsible?
液态水中分子热运动较强，氢键不断断裂和重建，分子排列较紧密；结冰时每个水分子通过氢键与周围四个水分子结合，形成开放的四面体网络，使冰的密度（约0.92克/立方厘米）小于液态水。因此冰浮在水面，湖泊也从上往下结冰，水底的水生生物得以存活。
In liquid water, thermal motion keeps breaking and reforming hydrogen bonds, so molecules pack more closely. On freezing, each molecule hydrogen-bonds to four neighbors, building an open tetrahedral network that makes ice less dense (~0.92 g/cm3) than liquid water. Ice therefore floats, lakes freeze top-down, and aquatic life survives below.
难度 进阶 · 适合 初中(12-15)
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出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
《普通化学》(Atkins) 分子间作用力章节
General Chemistry (Atkins), intermolecular forces
独立核验依据 · Independent verification: 核验依据 1 ARCHIVE 标识 intermolecularfo0000jeru：Intermolecular force
#氢键 #冰 #密度
什么是同素异形体？
What are allotropes?
同素异形体指同一种元素组成的不同单质，因原子排列或成键方式不同而有不同性质。碳的同素异形体包括金刚石、石墨、富勒烯和石墨烯。氧气与臭氧也是氧元素的同素异形体。
Allotropes are different forms of the same element as a pure substance, differing in atomic arrangement or bonding and thus in properties. Carbon allotropes include diamond, graphite, fullerenes and graphene. Oxygen and ozone are allotropes of oxygen.
难度 进阶 · 适合 初中(12-15)
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Housecroft 与 Sharpe《无机化学》（第5版，Pearson）同素异形体章节
Housecroft, C. E.; Sharpe, A. G. Inorganic Chemistry, 5th ed., Pearson (allotropes)
#同素异形体 #碳 #氧
水的相图上的三相点是什么意思？它和冰点是同一回事吗？
What is the triple point on the phase diagram of water, and is it the same as the freezing point?
三相点是液态水、冰和水蒸气三相共存的唯一温度和压强点，即0.01摄氏度和611.7帕，此时三相相互平衡。它与常说的大气压下冰点（0摄氏度）不同：冰点随压强改变，而三相点是热力学上固定的参考点。历史上开尔文温标曾以水的三相点（273.16 K）为基准定义，2019年国际单位制改版后改用玻尔兹曼常数定义，但三相点仍是重要的温度固定点。
The triple point is the unique temperature and pressure at which liquid water, ice and water vapor coexist in equilibrium - 0.01 degrees Celsius and 611.7 pascals. It differs from the familiar freezing point at 1 atmosphere (0 degrees Celsius), which shifts with pressure, while the triple point is a fixed thermodynamic reference. Historically the kelvin scale was defined via the water triple point (273.16 K); since the 2019 SI redefinition the kelvin is fixed through the Boltzmann constant, though the triple point remains an important temperature fixed point.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
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Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#相图 #三相点 #相平衡
为什么食盐溶于水却不溶于汽油？
Why does table salt dissolve in water but not in gasoline?
这是相似相溶规律。水是强极性分子，能通过离子-偶极作用把Na+和Cl-从晶格中拆散并包围起来；汽油是非极性碳氢化合物，几乎无法削弱氯化钠的离子键，所以盐在汽油中基本不溶解。极性溶剂溶解离子化合物或极性溶质，非极性溶剂溶解非极性溶质。
This is the like-dissolves-like rule. Water is strongly polar and pulls Na+ and Cl- apart from the lattice through ion-dipole interactions; gasoline is a nonpolar hydrocarbon that cannot weaken the ionic lattice, so salt hardly dissolves in it. Polar solvents dissolve ionic or polar solutes, while nonpolar solvents dissolve nonpolar solutes.
难度 进阶 · 适合 初中(12-15)
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《普通化学》(Atkins) 溶液章节
General Chemistry (Atkins), solutions
#溶解 #极性 #相似相溶
什么是晶体？
What is a crystal?
晶体是内部原子、离子或分子按一定规则周期性排列的固体，因此具有规则的几何外形和固定的熔点。常见的食盐、石英、雪花都是晶体。与之相对，玻璃等非晶体没有长程有序结构。
A crystal is a solid in which atoms, ions or molecules are arranged periodically according to a regular pattern, giving it a definite geometric shape and a fixed melting point. Common examples are table salt, quartz and snowflakes. In contrast, non-crystals like glass lack long-range order.
难度 入门 · 适合 大众
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Atkins 与 de Paula《物理化学》（第10版，牛津大学出版社）固体（晶体）章节
Atkins, P. W.; de Paula, J. Physical Chemistry, 10th ed., Oxford University Press (crystalline solids)
#晶体 #有序结构 #熔点
XeF₄ 的分子形状为什么是平面正方形？
Why is XeF₄ square planar in shape?
氙有 8 个价电子，与 4 个氟成键后剩余 2 对孤对电子。VSEPR 预测 6 个电子域呈八面体排布，两对孤对占据相对位置以最小化排斥，使 4 个氟位于同一平面形成正方形。
Xenon has 8 valence electrons; after bonding to 4 fluorines it keeps 2 lone pairs. VSEPR predicts 6 electron domains in an octahedron, and the two lone pairs sit opposite each other to minimize repulsion, leaving the 4 fluorines coplanar in a square.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
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大连理工大学无机化学教研室 编,《无机化学》第6版,高等教育出版社
Dalian University of Technology Inorganic Chemistry Group, Inorganic Chemistry, 6th ed., Higher Education Press
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040492750（豆瓣书目条目: 无机化学）
#VSEPR #孤对电子 #分子形状
什么是相变？
What is a phase transition?
相变是物质从一种相态转变为另一种相态的过程，如熔化、凝固、蒸发、冷凝和升华。相变通常伴随能量吸收或释放，但温度保持不变。冰融化成水就是在常压下的固液相变。
A phase transition is the change of a substance from one phase to another, such as melting, freezing, evaporation, condensation and sublimation. It usually involves absorbing or releasing energy while the temperature stays constant. Ice melting into water is a solid-liquid phase transition at normal pressure.
难度 入门 · 适合 大众
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Atkins 与 de Paula《物理化学》（第10版，牛津大学出版社）相变与相平衡章节
Atkins, P. W.; de Paula, J. Physical Chemistry, 10th ed., Oxford University Press (phase transitions)
#相变 #熔化 #蒸发
为什么糖在热水里比在冷水里溶得更快、也更多？
Why does sugar dissolve faster and more in hot water than in cold water?
溶解是糖分子脱离晶体、被水分子拉散开的过程，需要打破糖分子之间的相互作用。温度升高时水分子运动更剧烈、能提供的能量更多，所以既溶得快，最终能容纳的糖也更多（溶解度更高）。
Dissolving means sugar molecules breaking away from the crystal and being pulled apart by water, which requires overcoming sugar–sugar interactions. Higher temperature makes water molecules move more vigorously and supply more energy, so sugar dissolves both faster and to a greater amount (higher solubility).
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-11-03
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Brown, LeMay & Bursten《化学：中心科学》（第14版），第13章
Brown, LeMay & Bursten, "Chemistry: The Central Science" (14th ed.), Ch.13
独立核验依据 · Independent verification: 核验依据 1 ARCHIVE 标识 studentlectureno00theo：Chemistry, the central
#溶解度 #温度 #溶解 #糖