📚 Year 7 CCEA Chemistry: Core Knowledge Overview | Year 7 CCEA 化学：核心知识点梳理
Welcome to your Year 7 CCEA Chemistry revision guide. This article brings together the essential topics you will study this year, from the particle model to acids and alkalis, and explains each concept in clear, bite-sized chunks. Mastering these building blocks will give you a strong foundation for your Key Stage 3 science journey.
欢迎阅读 Year 7 CCEA 化学复习指南。这篇文章梳理了你将在这一年学习的所有必学主题，从粒子模型到酸与碱，并用清晰易懂的小模块逐一解释每个概念。掌握这些基础知识将为你整个 Key Stage 3 科学学习打下坚实的基础。
1. States of Matter | 物质的状态
All substances around you exist as one of three states of matter: solid, liquid or gas. The state depends on how the particles are arranged and how much energy they have.
你周围的所有物质都以三种状态之一存在：固态、液态或气态。物质所处的状态取决于粒子如何排列以及它们拥有多少能量。
In solids, the particles are tightly packed in a regular pattern, held together by strong forces. They can only vibrate in fixed positions, which is why solids keep a definite shape and volume.
在固体中，粒子以规则的图案紧密排列，被强大的吸引力固定住。它们只能在固定的位置上振动，这就是固体能保持确定形状和体积的原因。
In liquids, the particles are still close together but can slide past each other. This allows a liquid to flow and take the shape of the bottom of its container, while keeping a constant volume.
在液体中，粒子仍然彼此靠近，但可以互相滑过。这使得液体能够流动，并呈现容器底部的形状，同时保持恒定的体积。
In gases, the particles are spread far apart and move rapidly in all directions. A gas will fill its entire container and has no fixed shape or volume.
在气体中，粒子相距很远，并向各个方向快速运动。气体将充满整个容器，没有固定的形状或体积。
2. The Particle Model | 粒子模型
The particle model is a simple way to explain the behaviour of solids, liquids and gases. It tells us that all matter is made of tiny, invisible particles that are constantly moving.
粒子模型是解释固体、液体和气体行为的一种简单方法。它告诉我们，所有物质都由微小、看不见且不断运动的粒子组成。
Heating a substance gives the particles more kinetic energy. When a solid is heated strongly enough, the particles vibrate faster and break free from their fixed positions — the solid melts into a liquid.
加热物质会给粒子提供更多的动能。当固体被充分加热时，粒子振动加快并摆脱固定位置——固体熔化为液体。
If heating continues, the particles gain enough energy to overcome the attractions holding them close together. The liquid then turns into a gas, a process called boiling or evaporation.
如果继续加热，粒子会获得足够的能量去克服使它们彼此靠近的吸引力。然后液体变为气体，这个过程称为沸腾或蒸发。
3. Diffusion | 扩散
Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration. It happens in liquids and gases because the particles are free to move.
扩散是粒子从高浓度区域向低浓度区域扩散的过程。它发生在液体和气体中，因为粒子可以自由移动。
You can observe diffusion when a teaspoon of food colouring is added to a beaker of water. The colour gradually spreads until the whole beaker is evenly coloured, even without stirring.
当一茶匙食用色素加入一烧杯水中时，你可以观察到扩散。颜色逐渐散开，直到整个烧杯均匀着色，即使没有搅拌也是如此。
Diffusion is faster in gases than in liquids because gas particles move much more quickly and have larger spaces between them. It is also faster at higher temperatures.
气体中的扩散比液体中快得多，因为气体粒子运动得更快，且它们之间的空间更大。温度较高时扩散也更快。
4. Elements, Compounds and Mixtures | 元素、化合物与混合物
An element is a substance made of only one type of atom. Examples include oxygen, iron and carbon. There are about 118 known elements, and each has its own symbol on the periodic table.
元素是由仅一种原子组成的物质。例子包括氧、铁和碳。已知元素大约有118种，每一种在周期表中都有自己的符号。
A compound is a substance formed when two or more different elements chemically join together. The atoms are held by chemical bonds, and the compound has completely different properties from the original elements.
化合物是由两种或多种不同元素通过化学方式结合在一起形成的物质。原子由化学键固定，化合物的性质与原本的元素完全不同。
A mixture contains two or more substances that are physically combined but not chemically joined. You can often separate mixtures using simple techniques like filtration or evaporation.
混合物包含两种或多种物理混合但未通过化学方式结合的物质。通常可以用过滤或蒸发等简单技术来分离混合物。
5. Chemical Symbols and Formulae | 化学符号与化学式
Each element is represented by a chemical symbol, usually one or two letters. The first letter is always a capital letter, and the second, if there is one, is lower case.
每种元素都用一个化学符号表示，通常是一个或两个字母。第一个字母总是大写，第二个字母（如果有）小写。
For example, C stands for carbon, O for oxygen and Fe for iron. The symbols come from the element’s English or Latin name.
例如，C 代表碳，O 代表氧，Fe 代表铁。符号来源于元素的英文或拉丁文名称。
A chemical formula shows the types and numbers of atoms in a compound. H₂O tells us that water has two hydrogen atoms and one oxygen atom. CO₂ means one carbon atom and two oxygen atoms.
化学式表示化合物中原子的种类和数目。H₂O 告诉我们水分子含有两个氢原子和一个氧原子。CO₂ 表示一个碳原子和两个氧原子。
6. Physical and Chemical Changes | 物理变化与化学变化
A physical change alters the appearance or state of a material but does not make a new substance. Melting ice, dissolving sugar in water and cutting paper are all physical changes.
物理变化改变物质的外观或状态，但不产生新物质。冰融化、糖溶于水以及剪纸都属于物理变化。
Physical changes are usually easy to reverse. For example, you can freeze liquid water back into ice and evaporate the water from sugar solution to get the sugar back.
物理变化通常容易逆转。例如，你可以将液态水重新冻结成冰，也可以通过蒸发糖水来回收糖。
A chemical change produces one or more new substances. Once a chemical reaction happens, it is often difficult or impossible to reverse using simple physical methods.
化学变化会产生一种或多种新物质。一旦发生化学反应，通常很难或者不可能用简单的物理方法逆转。
7. Signs of a Chemical Reaction | 化学反应的迹象
We can tell that a chemical reaction has taken place by looking for certain signs. A colour change is a common clue — for instance, a blue solution turning green.
我们可以通过观察某些迹象来判断是否发生了化学反应。颜色变化是一个常见的线索——例如，蓝色溶液变成绿色。
A gas may be produced, seen as fizzing or bubbling in a liquid. The formation of a solid from two clear solutions, called a precipitate, is another strong sign.
可能会产生气体，表现为液体中的嘶嘶声或冒泡。两种清澈溶液中形成固体（称为沉淀）是另一个明显的标志。
An energy change is also a sign of a chemical reaction. Some reactions release heat and feel hot to touch (exothermic), while others absorb heat and feel cold (endothermic).
能量变化也是化学反应的迹象。有些反应释放热量，摸起来很热（放热反应），而另一些吸收热量，摸起来很冷（吸热反应）。
8. Acids and Alkalis | 酸与碱
Acids and alkalis are chemical opposites found in many everyday substances. Acids have a sharp, sour taste and include vinegar, citrus fruit juice and fizzy drinks.
酸和碱是化学上的对立物，存在于许多日常物质中。酸有刺激性的酸味，包括醋、柑橘类果汁和汽水。
Common alkalis feel soapy to touch and include baking powder, soap and bleach. Strong acids and strong alkalis are corrosive and must be handled with care.
常见的碱摸起来有滑腻感，包括发酵粉、肥皂和漂白剂。强酸和强碱具有腐蚀性，必须小心处理。
We use indicators to test whether a substance is acidic or alkaline. Litmus is a simple indicator that turns red in acids and blue in alkalis.
我们使用指示剂来测试物质是酸性还是碱性。石蕊是一种简单的指示剂，在酸中变红，在碱中变蓝。
9. The pH Scale | pH标度
The pH scale is a number scale from 0 to 14 that tells us how acidic or alkaline a solution is. Universal indicator is a mixture of dyes that shows a range of colours depending on the pH.
pH标度是一个从0到14的数字标度，用来表示溶液的酸性或碱性强弱。通用指示剂是染料的混合物，根据pH值显示一系列颜色。
A pH of 7 is neutral, like pure water. Solutions with a pH less than 7 are acidic; the lower the number, the stronger the acid.
pH为7表示中性，如纯水。pH小于7的溶液呈酸性；数字越小，酸性越强。
Solutions with a pH greater than 7 are alkaline; the higher the number, the stronger the alkali. pH 0–2 indicates a strong acid, while pH 12–14 indicates a strong alkali.
pH大于7的溶液呈碱性；数字越大，碱性越强。pH 0–2表示强酸，pH 12–14表示强碱。
10. Neutralisation | 中和反应
Neutralisation is a chemical reaction between an acid and an alkali that makes a salt and water. The general word equation is: acid + alkali → salt + water.
中和反应是酸和碱之间发生的化学反应，生成盐和水。通用的文字方程式是：酸 + 碱 → 盐 + 水。
When an acid and an alkali are mixed in exactly the right proportions, the pH of the resulting solution becomes 7. The solution is neutral and no longer harmful.
当酸和碱以恰好正确的比例混合时，所得溶液的pH值变为7。该溶液为中性，不再有危害。
Neutralisation is useful in everyday life: farmers use lime (an alkali) to neutralise acidic soil, and toothpaste contains weak alkalis to neutralise acids in the mouth.
中和反应在日常生活中很有用：农民用石灰（一种碱）来中和酸性土壤，牙膏中含有弱碱以中和口腔中的酸。
11. Separating Mixtures | 混合物的分离
Because the substances in a mixture are not chemically joined, we can separate them using physical techniques. The choice of method depends on the properties of the substances present.
由于混合物中的物质不是通过化学方式结合的，我们可以用物理技术将它们分开。方法的选择取决于混合物中各组分的性质。
Filtration is used to separate an insoluble solid from a liquid. For example, filter paper can trap sand while letting water pass through.
过滤用于将不溶性固体从液体中分离出来。例如，滤纸可以截留沙子，同时让水通过。
Evaporation is used to collect a dissolved solid from a solution. Heating the solution causes the liquid to evaporate, leaving the solid behind as crystals.
蒸发用于从溶液中收集溶解的固体。加热溶液使液体蒸发，留下固体作为晶体。
Distillation separates a liquid from a solution by boiling and then condensing the vapour. Chromatography can separate coloured substances like the dyes in ink.
蒸馏通过沸腾再冷凝蒸气的方式从溶液中分离出液体。色谱法可以分离有色物质，比如墨水中的染料。
12. Key Practical Skills | 关键实验技能
Working safely in the laboratory is the first priority. Always wear safety goggles, tie back long hair, and stand up when handling chemicals.
在实验室安全操作是第一要务。始终佩戴护目镜，把长发扎起来，处理化学品时要站起来。
Learn the names of common apparatus: beaker, conical flask, test tube, Bunsen burner, tripod and gauze. Knowing how to use them safely helps you carry out experiments with confidence.
学会常见仪器的名称：烧杯、锥形瓶、试管、本生灯、三脚架和石棉网。知道如何安全使用它们可以帮助你自信地进行实验。
When heating a substance, use a blue flame on the Bunsen burner for gentle heating and move the apparatus smoothly through the flame to avoid hotspots.
加热物质时，使用本生灯的蓝色火焰进行温和加热，并让仪器均匀地穿过火焰，以避免局部过热。
Recording observations clearly is a vital skill. Always write down what you see, hear or measure, and use a results table where possible to keep your data organised.
清晰地记录观察是一项重要技能。始终记下你看到、听到或测量的内容，并尽可能使用结果表来让数据井井有条。
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