📚 Year 7 CCEA Chemistry: Quick Reference to Formulas and Principles | 七年级 CCEA 化学：公式定理速查手册
This article provides a clear and concise summary of the essential formulas, laws and concepts needed for the CCEA Year 7 Chemistry curriculum. Each section presents key ideas in paired English and Chinese paragraphs to help you learn, revise and check your understanding quickly.
本文清晰简明地总结了CCEA七年级化学课程中必备的核心公式、定律和概念。每个小节都以中英对照的段落呈现关键知识，帮助你快速学习、复习和检验理解。
1. The Particle Model | 粒子模型
All matter is made up of tiny particles that are constantly moving. The way these particles are arranged and how they move determines the state of the substance.
所有物质都由不断运动的微小粒子构成。这些粒子的排列方式和运动方式决定了物质的状态。
There are spaces between particles. In solids the particles are tightly packed, in liquids they are close but can slide past each other, and in gases they are far apart and move rapidly in all directions.
粒子之间存在空隙。固体中粒子紧密堆积，液体中粒子靠得很近但可以相互滑动，气体中粒子相隔很远并快速向各个方向运动。
When a substance is heated, its particles gain energy and move faster. This can cause a change of state as the forces holding the particles together are overcome.
物质受热时，粒子获得能量并运动加快。当维持粒子间结合的力被克服时，就可能发生状态变化。
2. States of Matter | 物质状态
There are three common states of matter: solid, liquid and gas. A solid has a fixed shape and volume, a liquid has a fixed volume but takes the shape of its container, and a gas has no fixed shape or volume.
物质常见有三态：固体、液体和气体。固体有固定的形状和体积，液体有固定的体积但取容器的形状，气体没有固定的形状或体积。
In terms of particle behaviour, solids vibrate in fixed positions, liquids move around each other, and gases move freely at high speed. This is why solids are rigid, liquids flow, and gases expand to fill a container.
就粒子行为而言，固体在固定位置上振动，液体相互围绕运动，气体高速自由运动。这就是固体坚硬、液体能流动、气体会膨胀充满容器的原因。
3. Changes of State | 物态变化
Melting is the change from solid to liquid at the melting point. Freezing is the reverse change from liquid to solid. Both processes involve heat energy being transferred.
熔化是固体在熔点转变为液体的过程。凝固是液体变为固体的逆过程。这两个过程都涉及热量的传递。
Boiling and evaporation are ways a liquid turns into a gas. Boiling happens throughout the liquid at the boiling point, while evaporation occurs only at the surface and can happen at temperatures below the boiling point. Condensation is the change from gas back to liquid.
沸腾和蒸发是液体变为气体的方式。沸腾在整个液体中发生，需要达到沸点；蒸发仅发生在液面，在低于沸点的温度下也能进行。冷凝是气体变回液体的过程。
Sublimation is the rare change from solid directly to gas, like dry ice (solid carbon dioxide) turning into carbon dioxide gas without first becoming a liquid.
升华是固体直接变为气体的少见变化，例如干冰（固态二氧化碳）不经过液态直接变为二氧化碳气体。
4. Elements, Compounds and Mixtures | 元素、化合物与混合物
An element is a pure substance made of only one type of atom. It cannot be broken down into simpler substances by chemical means. Examples include oxygen (O), iron (Fe) and gold (Au).
元素是一种只含一种原子的纯物质，不能通过化学方法分解成更简单的物质。例子有氧（O）、铁（Fe）和金（Au）。
A compound is a pure substance formed when two or more different elements are chemically combined. The atoms are held together by chemical bonds, giving the compound properties different from its original elements. Water (H₂O) is a compound made of hydrogen and oxygen.
化合物是由两种或多种不同元素通过化学结合形成的纯物质。原子通过化学键结合在一起，使化合物具有不同于原有元素的性质。水（H₂O）是由氢和氧组成的化合物。
A mixture contains two or more substances (elements and/or compounds) that are physically combined and not chemically bonded. Mixtures can be separated by physical methods such as filtration or distillation. Air is a mixture of gases.
混合物含有两种或多种物质（元素和/或化合物），它们只是物理混合，没有化学键合。混合物可以通过过滤或蒸馏等物理方法分离。空气是气体的混合物。
5. Atoms and Molecules | 原子与分子
An atom is the smallest particle of an element that still has the properties of that element. Atoms consist of a central nucleus containing protons and neutrons, surrounded by electrons moving in shells.
原子是元素最小的粒子，仍然保留该元素的性质。原子由中心的原子核（含质子和中子）以及核外分层运动的电子组成。
A molecule is a group of two or more atoms held together by covalent bonds. Molecules can be elements (e.g. O₂) or compounds (e.g. CO₂). The chemical formula tells us the number and type of atoms in a molecule.
分子是由两个或更多原子通过共价键结合而成的基团。分子可以是元素（如O₂），也可以是化合物（如CO₂）。化学式告诉我们分子中原子的种类和数量。
In chemical reactions, atoms are rearranged but not created or destroyed. This idea is expressed by the Law of Conservation of Mass.
在化学反应中，原子重新排列，但不会被创造或消灭。这一思想由质量守恒定律表达。
6. Chemical Reactions & Conservation of Mass | 化学反应与质量守恒
A chemical reaction occurs when substances (reactants) change into new substances (products). Signs of a reaction include colour change, gas production, temperature change, precipitate formation, or an odour being given off.
当物质（反应物）转变为新物质（生成物）时，就发生了化学反应。反应的迹象包括颜色变化、产生气体、温度变化、生成沉淀或发出气味。
The Law of Conservation of Mass states that in a chemical reaction, the total mass of the reactants equals the total mass of the products. Atoms are simply rearranged, so mass stays the same.
质量守恒定律指出，在化学反应中，反应物的总质量等于生成物的总质量。原子只是重新排列，因此质量保持不变。
A word equation describes a reaction using the names of reactants and products. For example: magnesium + oxygen → magnesium oxide. Symbol equations are more concise and use chemical symbols.
文字方程式用反应物和生成物的名称描述反应，例如：镁 + 氧气 → 氧化镁。符号方程式更简洁，使用化学符号。
7. Acids and Alkalis | 酸与碱
Acids are substances that release hydrogen ions (H⁺) when dissolved in water. They have a sour taste (though tasting is never done in the lab) and turn blue litmus paper red. Common laboratory acids include hydrochloric acid, sulfuric acid and nitric acid.
酸是溶于水时释放氢离子（H⁺）的物质。它们有酸味（但实验室内绝不可品尝），能使蓝色石蕊试纸变红。常见的实验室酸包括盐酸、硫酸和硝酸。
Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. They feel soapy and turn red litmus paper blue. Sodium hydroxide and potassium hydroxide are common alkalis.
碱是可溶的碱，能在水中释放氢氧根离子（OH⁻）。碱有滑腻感，能使红色石蕊试纸变蓝。氢氧化钠和氢氧化钾是常见的碱。
The pH scale measures how acidic or alkaline a solution is. Values below 7 are acidic, 7 is neutral, and above 7 are alkaline. Universal indicator shows a range of colours depending on pH.
pH标度用来衡量溶液的酸碱性。低于7为酸性，7为中性，高于7为碱性。通用指示剂根据pH值显示不同颜色。
When an acid and an alkali react, they neutralise each other, producing a salt and water. This is called a neutralisation reaction: acid + alkali → salt + water.
酸和碱反应时会彼此中和，生成盐和水。这称为中和反应：酸 + 碱 → 盐 + 水。
8. The Reactivity Series | 金属活动性顺序
The reactivity series lists metals in order of how vigorously they react with other substances such as water, acids and oxygen. A common mnemonic helps remember the order: Please Stop Calling My Aunt Zelda In The Library – Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Tin, Lead.
金属活动性顺序按金属与水、酸和氧气反应的剧烈程度排列。一个常见的记忆口诀帮助记住顺序：钾钠钙镁铝锌铁锡铅（对应英文首字母）。
More reactive metals can displace less reactive metals from their compounds. For example, magnesium + copper sulfate → magnesium sulfate + copper. This is a displacement reaction.
较活泼的金属可以从较不活泼金属的化合物中将其置换出来。例如：镁 + 硫酸铜 → 硫酸镁 + 铜。这是一个置换反应。
Metals react with oxygen to form metal oxides, a process called oxidation. Rusting is the oxidation of iron in the presence of water and oxygen. Less reactive metals like gold do not corrode easily.
金属与氧反应生成金属氧化物，这过程称为氧化。生锈是铁在水和氧气存在下的氧化。像金这样不活泼的金属不易腐蚀。
9. Separating Mixtures | 混合物分离方法
Filtration separates an insoluble solid from a liquid. A filter paper lets the liquid pass through (filtrate) while the solid (residue) stays behind. This is used to separate sand from water.
过滤用于将不溶性固体与液体分离。滤纸让液体通过（滤液），而固体（残渣）被截留。这常用于分离沙和水。
Evaporation removes a soluble solid from a solution by heating the solution until the liquid evaporates, leaving the solid behind. Distillation separates a solvent from a solution by boiling then condensing, collecting the pure liquid.
蒸发通过加热溶液使液体蒸发，留下固体，从而从溶液中分离出可溶性固体。蒸馏是先沸腾再冷凝，收集纯液体，将溶剂从溶液中分离出来。
Chromatography separates dissolved substances, such as the coloured dyes in ink. The mixture moves through a stationary phase (paper), and different substances travel at different speeds, creating separate spots.
色谱法用于分离溶解的物质，例如墨水中的有色染料。混合物在固定相（纸）上移动，不同物质以不同的速度迁移，形成分离的斑点。
10. Solutions and Solubility | 溶液与溶解度
A solution is formed when a solute dissolves in a solvent. The solute is the substance that dissolves, and the solvent is the liquid that does the dissolving. In salt water, salt is the solute and water is the solvent.
当溶质溶解在溶剂中时形成溶液。溶质是被溶解的物质，溶剂是进行溶解的液体。在盐水中，盐是溶质，水是溶剂。
Solubility is a measure of how much solute can dissolve in a given amount of solvent at a certain temperature. Usually, solubility of solids increases with temperature, while gases become less soluble as temperature rises.
溶解度是在特定温度下，一定量溶剂中最多能溶解多少溶质的量度。通常，固体溶解度随温度升高而增大，而气体溶解度随温度升高而减小。
A saturated solution is one in which no more solute can dissolve at that temperature. Any extra solute added will simply settle at the bottom.
饱和溶液是指在该温度下不能再溶解更多溶质的溶液。任何额外加入的溶质只会沉在底部。
11. Diffusion | 扩散
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient. It is a passive process that does not require energy.
扩散是粒子从高浓度区域向低浓度区域的净运动，顺着浓度梯度进行。这是一个被动过程，不需要能量。
Diffusion occurs in liquids and gases because the particles are constantly moving. It is faster at higher temperatures as particles have more kinetic energy. A smaller particle mass also leads to faster diffusion.
扩散在液体和气体中发生，因为粒子在不断运动。温度越高扩散越快，因为粒子动能更大。粒子质量越小，扩散也越快。
Real-life examples include the smell of perfume spreading in a room and the movement of oxygen from the air into our blood in the lungs. In chemistry labs, diffusion can be demonstrated by watching coloured solutes spread in water.
现实例子包括香水气味在房间里散开，以及氧气从空气进入肺部的血液。在化学实验中，可通过观察有色溶质在水中扩散来演示扩散。
12. Key Formulas & Equations | 关键公式与方程式
The following formulas and relationships are useful throughout Year 7 chemistry. Understanding these helps build a strong foundation for later topics.
以下公式和关系在七年级化学全过程中都很有用。理解它们有助于为后续课题打下坚实基础。
Density (ρ) = mass (m) ÷ volume (V)
Density tells us how much mass is packed into a unit volume. If density is greater than water (1 g/cm³), the object sinks.
密度告诉我们单位体积内有多少质量。如果密度大于水（1 g/cm³），物体会下沉。
Concentration = mass of solute (g) / volume of solution (dm³)
Often, concentration is measured in grams per cubic decimetre (g/dm³). This formula helps calculate how strong a solution is.
浓度常以克每立方分米（g/dm³）为单位。该公式用于计算溶液的浓淡程度。
Rate of reaction ≈ quantity of product formed ÷ time taken
While Year 7 students do not need to calculate exact rates, the idea that the rate depends on the speed at which reactants are used up or products appear is key. Temperature, surface area and concentration can all affect this rate.
虽然七年级学生不需要计算精确的速率，但反应速率取决于反应物消耗或生成物出现的快慢这一概念很重要。温度、表面积和浓度都能影响速率。
General word equations to remember:
- metal + oxygen → metal oxide
- metal + water → metal hydroxide + hydrogen (for reactive metals)
- metal + acid → salt + hydrogen
- acid + alkali → salt + water
- carbonate + acid → salt + water + carbon dioxide
需记住的通用文字方程式：
- 金属 + 氧气 → 金属氧化物
- 金属 + 水 → 金属氢氧化物 + 氢气（对于活泼金属）
- 金属 + 酸 → 盐 + 氢气
- 酸 + 碱 → 盐 + 水
- 碳酸盐 + 酸 → 盐 + 水 + 二氧化碳
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