📚 Introduction to the Particulate Nature of Matter and Chemical Change | 物质微粒性质与化学变化导论
Chemistry is the study of matter and the changes it undergoes. To understand why substances behave as they do, we must first explore the particulate nature of matter – the idea that all substances are made up of tiny, moving particles. This fundamental concept explains the states of matter, diffusion, and the difference between physical and chemical changes.
化学是研究物质及其变化的学科。要理解物质为何表现出特定的行为，我们必须首先探索物质的微粒性质——即所有物质都由微小的、不断运动的粒子构成的观念。这一基本概念能解释物质的状态、扩散现象，以及物理变化和化学变化之间的区别。
1. The Three States of Matter | 物质的三态
Matter typically exists in one of three physical states: solid, liquid or gas. In a solid, particles are packed closely in a regular pattern and can only vibrate in fixed positions. This gives solids a definite shape and volume. In a liquid, particles are still close together but are arranged randomly and can slide past one another, allowing liquids to flow and take the shape of their container while maintaining a fixed volume. In a gas, particles are far apart, move rapidly in all directions, and have no fixed shape or volume; they fill any container completely.
物质通常以三种物理状态之一存在：固态、液态或气态。固体中，粒子紧密排列成有规则的图案，只能在固定位置振动，因此固体具有固定的形状和体积。液体中，粒子仍然紧密聚集，但呈无序排列，可以相互滑动，因此液体能够流动，盛装时呈容器形状，但保持固定的体积。气体中，粒子相距较远，向各个方向快速运动，没有固定的形状或体积，会完全充满任何容器。
2. Kinetic Particle Theory | 粒子运动论
The kinetic particle theory states that all matter consists of small particles in constant motion. The energy of these particles is called kinetic energy, and the average kinetic energy increases with temperature. This theory explains the properties of solids, liquids and gases: the stronger the forces of attraction between particles relative to their kinetic energy, the more ordered the arrangement. Heating a substance increases the particles' kinetic energy, causing them to move faster and eventually overcome the attractive forces, resulting in a change of state.
粒子运动论指出，所有物质都由不断运动的小粒子组成。这些粒子的能量称为动能，平均动能随温度升高而增加。该理论解释了固体、液体和气体的性质：粒子间吸引力相对于动能越大，排列越有序。加热物质会增加粒子的动能，使它们运动得更快，最终克服吸引力，从而导致状态变化。
3. Changes of State | 状态变化
lso undergo sublimation (solid → gas directly, e.g. solid carbon dioxide) and deposition (gas → solid). During these changes, the particles themselves are not altered, only their arrangement and motion change.
物质三种状态之间的相互转化是物理过程。熔化（固→液）和沸腾或蒸发（液→气）发生在加热时。凝固（液→固）和凝结（气→液）发生在冷却时。某些物质还可以经历升华（固体直接变为气体，例如固体二氧化碳）和凝华（气体直接变为固体）。在这些变化过程中，粒子本身并未改变，只是它们的排列和运动方式发生了变化。
4. Diffusion: Evidence for Moving Particles | 扩散：粒子运动的证据
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration as a result of their random motion. The classic demonstration uses ammonia (NH₃) and hydrogen chloride (HCl) vapour: a white ring of ammonium chloride forms closer to the HCl source because ammonia particles diffuse faster (lower molar mass). Diffusion provides strong evidence for the kinetic particle theory and shows that there are spaces between particles, especially in gases.
扩散是粒子由于随机运动而从高浓度区域向低浓度区域净移动的现象。经典演示实验使用氨气（NH₃）和氯化氢（HCl）蒸气：在离HCl源较近处形成氯化铵的白色环，因为氨粒子扩散较快（摩尔质量较低）。扩散为粒子运动论提供了有力的证据，并表明粒子之间存在空隙，尤其是在气体中。
5. Atoms, Molecules and Ions | 原子、分子和离子
Atoms are the smallest particles of an element that can take part in chemical change. Molecules are groups of two or more atoms held together by covalent bonds; they can be elements (e.g. O₂, N₂) or compounds (e.g. H₂O, CO₂). Ions are charged particles formed when atoms or groups of atoms lose or gain electrons. Cations are positively charged (e.g. Na⁺, Mg²⁺) and anions are negatively charged (e.g. Cl⁻, SO₄²⁻). Ionic compounds consist of a regular lattice of positive and negative ions.
原子是能参与化学变化的元素的最小粒子。分子是由两个或多个原子通过共价键结合在一起组成的群体；它们可以是单质（如 O₂、N₂），也可以是化合物（如 H₂O、CO₂）。离子是原子或原子团失去或获得电子后形成的带电粒子。阳离子带正电（如 Na⁺、Mg²⁺），阴离子带负电（如 Cl⁻、SO₄²⁻）。离子化合物由正负离子规则排列的晶格构成。
6. Elements, Compounds and Mixtures | 单质、化合物和混合物
An element is a pure substance made of only one type of atom. A compound is a pure substance composed of two or more different elements chemically combined in fixed proportions. A mixture contains two or more substances (elements or compounds) physically mixed together, not chemically bonded. Mixtures can often be separated by physical techniques such as filtration, distillation or chromatography.
单质是由同一种原子组成的纯净物。化合物是由两种或多种不同元素按固定比例通过化学结合而成的纯净物。混合物包含两种或多种物质（单质或化合物）物理混合在一起，没有化学键合。混合物通常可以通过过滤、蒸馏或色谱法等物理技术进行分离。
7. Physical Change vs Chemical Change | 物理变化与化学变化
A physical change alters the appearance or state of a substance but no new substances are formed. Examples include melting ice, dissolving salt in water, and cutting paper. A chemical change (or chemical reaction) involves the rearrangement of atoms to form one or more new substances with different properties. Burning wood, rusting iron and cooking an egg are all chemical changes. The key difference is whether the chemical identity of the substance changes.
物理变化会改变物质的外观或状态，但没有新物质生成。例子包括冰融化、食盐溶于水、剪纸。化学变化（或化学反应）涉及原子的重新排列，生成一种或多种性质不同的新物质。木材燃烧、铁生锈和煮熟鸡蛋都属于化学变化。两者的关键区别在于物质的化学标识是否发生了变化。
8. Identifying Chemical Change | 化学变化的识别
Several observations can indicate a chemical change: a colour change (e.g. silver jewellery tarnishing), formation of a precipitate (solid formed when two solutions are mixed), evolution of a gas (bubbles in a mixture without heating), an energy change (heat or light released or absorbed), and occasionally a noticeable smell. These changes are often irreversible, though some reactions can be reversed under certain conditions.
多种观察现象可以表明发生了化学变化：颜色变化（例如银饰品变暗）、沉淀生成（两种溶液混合时生成固体）、气体产生（不加热时混合物中出现气泡）、能量变化（放出或吸收热量或光），偶尔还有明显的气味变化。这些变化通常是不可逆的，尽管某些反应在特定条件下可以逆转。
9. Representing Chemical Change: Word Equations | 表示化学变化：文字方程式
reactants and products. The general format is: reactants → products, where the arrow means 'yields' or 'produces' ive information, they are a useful first step in modelling what happens during a reaction.
文字方程式使用反应物和生成物的名称来描述化学反应。常见格式为：反应物 → 生成物，箭头表示“生成”。例如：镁 + 氧气 → 氧化镁。文字方程式虽然不提供定量信息，但它们是建模反应过程的有用第一步。
10. From Word to Symbol Equations | 从文字到符号方程式
the unbalanced equation Mg + O₂ → MgO becomes 2Mg + O₂ → 2MgO. State symbols (s), (l), (g) and (aq) indicate the physical states of the substances.
符号方程式使用化学式表示反应物和生成物，并且必须配平以遵守质量守恒定律。配平涉及在化学式前放置系数，使箭头两边每种元素的原子数目相等。例如，未配平的方程式 Mg + O₂ → MgO 经配平后成为 2Mg + O₂ → 2MgO。状态符号 (s)、(l)、(g) 和 (aq) 表示物质的物理状态。
11. The Law of Conservation of Mass | 质量守恒定律
The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. Therefore, the total mass of reactants always equals the total mass of products. In terms of particles, the atoms present before the reaction are simply rearranged; no atoms are lost or gained. Experimental verification, such as precipitating silver chloride and measuring the mass before and after mixing, confirms this fundamental law.
质量守恒定律指出，在化学反应中，物质既不能被创造也不能被消灭。因此，反应物的总质量总是等于生成物的总质量。从粒子角度来看，反应前的原子只是进行了重新排列；没有原子丢失或增加。通过实验验证，例如沉淀氯化银并测量混合前后的质量，能证实这一定律。
12. The Mole Concept – An Introduction | 物质的量的概念——导论
to count them. One mole of any substance contains exactly 6.022 × 10²³ particles (Avogadro' mula mass. The mole links the particle world to the macroscopic world, allowing us to calculate quantities in reactions. For example, 12 g of carbon-12 contains one mole of carbon atoms.
由于原子和分子极其微小，化学家使用摩尔（mol）来计量它们。一摩尔任何物质都恰好包含 6.022 × 10²³ 个粒子（阿伏伽德罗常数）。一摩尔元素或化合物的质量即为其以克每摩尔为单位的摩尔质量，数值上等于其相对原子质量或化学式量。摩尔将粒子世界与宏观世界联系起来，使我们能够计算反应中的各种量。例如，12 克碳-12 含有一摩尔碳原子。
Published by TutorHao | Chemistry Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图