📚 Year 7 Edexcel Science: Core Knowledge Summary | Year 7 Edexcel 科学：核心知识点梳理
Welcome to your comprehensive guide to Year 7 Edexcel Science. This article brings together the essential knowledge you need across biology, chemistry and physics, covering everything from the building blocks of life to the principles that govern forces and electricity. Whether you are revising for an end-of-topic test or building a strong foundation for Key Stage 3, these core ideas will help you explain the world around you with confidence.
欢迎阅读 Year 7 Edexcel 科学核心知识点全面梳理。本文汇总了你在生物、化学和物理学科中必须掌握的关键知识，从生命的构成单元到支配力与电学的原理。无论你是在准备单元测验，还是在为 KS3 打下扎实基础，这些核心概念都能帮助你自信地解释身边的世界。
1. Cells and Microscopes | 细胞与显微镜
All living things are made of cells, which are the basic structural and functional units of life. Some organisms, like bacteria and amoeba, are unicellular (made of a single cell), while plants and animals are multicellular and contain many different types of cells that work together.
所有生物都由细胞构成，细胞是生命的基本结构和功能单位。一些生物，如细菌和变形虫，是单细胞的（只由一个细胞构成），而植物和动物是多细胞的，包含许多不同类型的细胞协同工作。
We use light microscopes to magnify cells and see their internal structures. A typical school microscope has an eyepiece lens (usually ×10) and several objective lenses (e.g., ×4, ×10, ×40). The total magnification is calculated by multiplying the magnification of the eyepiece lens by that of the objective lens in use.
我们使用光学显微镜来放大细胞并观察其内部结构。一台典型的学校显微镜有一个目镜（通常为 ×10）和几个物镜（例如 ×4、×10、×40）。总放大倍数的计算方法是目镜放大倍数乘以正在使用的物镜放大倍数。
Total magnification = Eyepiece magnification × Objective magnification
Most animal cells share three common parts: a nucleus that controls the cell’s activities and contains genetic material, cytoplasm where chemical reactions occur, and a cell membrane that controls what enters and leaves the cell. Plant cells have the same three parts plus a rigid cell wall made of cellulose, chloroplasts that absorb light for photosynthesis, and a large permanent vacuole filled with cell sap.
大多数动物细胞都有三个共同部分：控制细胞活动并含有遗传物质的细胞核，进行化学反应的细胞质，以及控制物质进出的细胞膜。植物细胞除了这三者外，还有由纤维素构成的坚硬细胞壁、吸收光能进行光合作用的叶绿体，以及充满细胞液的大液泡。
Many cells are specialised to carry out particular functions. For example, red blood cells have no nucleus to make more room for haemoglobin and are shaped like biconcave discs, nerve cells are long to transmit electrical impulses quickly, and root hair cells have a large surface area to absorb water and minerals from the soil.
许多细胞特化以执行特定功能。例如，红细胞没有细胞核，以便为血红蛋白腾出更多空间，并呈双凹圆盘状；神经细胞很长，可以快速传递电信号；根毛细胞具有较大的表面积，可以从土壤中吸收水分和矿物质。
2. Levels of Organisation | 组织层次
In multicellular organisms, cells do not work in isolation. They are organised into levels of increasing complexity. A group of similar cells working together forms a tissue. Different tissues combine to make an organ, and organs work together in organ systems.
在多细胞生物中，细胞不是孤立工作的。它们按照复杂度递增的层次组织起来。一群相似的细胞共同工作形成组织。不同的组织组合形成器官，多个器官协同工作构成器官系统。
For example, in the human digestive system, muscle cells make up muscle tissue in the stomach wall, which contracts to churn food. The stomach is an organ made of muscle tissue, glandular tissue and epithelial tissue. The stomach, intestines, liver and pancreas together form the digestive system, which breaks down food and absorbs nutrients. The whole living individual is the organism.
例如，在人体消化系统中，肌肉细胞构成胃壁的肌肉组织，通过收缩搅拌食物。胃是一个器官，由肌肉组织、腺体组织和上皮组织构成。胃、肠、肝脏和胰腺共同构成消化系统，负责分解食物并吸收营养。整个生命体就是生物个体。
This hierarchy – cells, tissues, organs, organ systems, organism – applies not only to humans but to all complex animals and plants. Recognising these levels helps scientists understand how structures relate to functions.
这个层次结构——细胞、组织、器官、器官系统、生物体——不仅适用于人类，也适用于所有复杂的动植物。认识这些层次有助于科学家理解结构与功能之间的关系。
3. Skeleton and Muscles | 骨骼与肌肉
The human skeleton provides several vital functions. It supports the body, protects delicate organs (the skull protects the brain and the ribcage protects the heart and lungs), allows movement by providing attachment points for muscles, and produces blood cells in the bone marrow.
人体骨骼具有多项重要功能。它支撑身体，保护脆弱的器官（颅骨保护大脑，胸廓保护心脏和肺），通过提供肌肉附着点来实现运动，并在骨髓中制造血细胞。
Joints are places where two or more bones meet. Movable joints are classified by the type of movement they allow. A hinge joint, such as the elbow or knee, allows movement in one plane (like the opening and closing of a door). A ball and socket joint, such as the shoulder or hip, allows movement in many directions and rotation.
关节是两块或多块骨头连接的地方。可动关节根据其允许的运动类型进行分类。铰链关节，如肘关节或膝关节，允许在一个平面上运动（像门的开合）。球窝关节，如肩关节或髋关节，允许多个方向的运动和旋转。
Muscles can only pull; they cannot push. Therefore, they work in antagonistic pairs across a joint. To bend the arm at the elbow, the biceps muscle contracts and pulls on the radius bone, while the triceps muscle relaxes. To straighten the arm, the triceps contracts and the biceps relaxes. This coordinated contraction and relaxation produces smooth movement.
肌肉只能拉，不能推。因此，它们跨关节成对拮抗工作。要弯曲手臂，肱二头肌收缩并拉动桡骨，同时肱三头肌舒张。要伸直手臂，肱三头肌收缩，肱二头肌舒张。这种协调的收缩与舒张产生了流畅的运动。
4. Reproduction in Animals | 动物生殖
Sexual reproduction involves the fusion of male and female gametes. In animals, the male gamete is the sperm cell and the female gamete is the egg cell (ovum). Both are specialised cells: the sperm has a tail to swim, and the egg contains a store of nutrients.
有性生殖涉及雄性和雌性配子的融合。在动物中，雄性配子是精子，雌性配子是卵细胞。两者都是特化细胞：精子有尾巴用于游动，卵子含有营养储备。
Fertilisation happens when the nucleus of a sperm cell fuses with the nucleus of an egg cell, forming a single new cell called a zygote. This zygote then divides many times to form an embryo, which implants in the uterus wall and develops during gestation. In humans, the developing baby receives oxygen and nutrients from the mother through the placenta and is protected inside the amniotic sac.
当精子细胞核与卵细胞核融合时，受精便发生，形成一个称为受精卵的新细胞。受精卵随后多次分裂形成胚胎，胚胎在子宫壁着床并在妊娠期间发育。在人体内，发育中的胎儿通过胎盘从母体获得氧气和营养，并受羊膜囊的保护。
Puberty is the stage of development when the reproductive organs mature and secondary sexual characteristics develop. In boys, the testes start producing sperm and the voice deepens; in girls, the ovaries start releasing eggs and menstruation begins. These changes are controlled by hormones.
青春期是生殖器官成熟且第二性征发育的阶段。男孩的睾丸开始产生精子，声音变得低沉；女孩的卵巢开始排卵，月经来潮。这些变化由激素控制。
5. Particles and States of Matter | 粒子与物质状态
The particle model describes how all substances are made up of tiny, moving particles. The arrangement and movement of these particles determine whether a substance is a solid, liquid or gas. The particles themselves do not change; it is their spacing and motion that vary.
粒子模型描述了所有物质都由微小的、运动的粒子构成。这些粒子的排列和运动方式决定了物质是固体、液体还是气体。粒子本身不会改变，变化的是它们的间距和运动。
In solids, particles are packed closely in a fixed, regular arrangement. They vibrate in place but cannot move around, which gives solids a definite shape and volume. In liquids, particles are still close together but are arranged randomly and can slide past each other, allowing liquids to flow and take the shape of their container. In gases, particles are far apart with no regular arrangement, moving rapidly in all directions; gases have no fixed shape or volume and can be compressed easily.
在固体中，粒子紧密堆积成固定、规则的排列。它们只能在原位振动，无法自由移动，因此固体有固定的形状和体积。在液体中，粒子仍然紧靠在一起，但排列随机，并且可以相互滑动，这使得液体能够流动并取容器的形状。在气体中，粒子相距很远，没有规则排列，向各个方向快速运动；气体没有固定的形状或体积，且容易被压缩。
Changes of state are physical changes where energy is transferred to or from the particles. Melting (solid to liquid) and boiling (liquid to gas) require energy input, while freezing and condensing release energy. The mass of a substance stays the same during changes of state because the number of particles does not change – this is conservation of mass.
状态变化是物理变化，涉及粒子获得或失去能量。熔化（固变液）和沸腾（液变气）需要输入能量，而凝固和冷凝释放能量。状态变化时物质的质量保持不变，因为粒子数量没有改变——这就是质量守恒。
6. Atoms, Elements and Compounds | 原子、元素与化合物
All substances are made from atoms, which are the smallest particles of an element that can take part in chemical reactions. An element is a pure substance made up of only one type of atom, and each element has its own chemical symbol. For example, oxygen is represented by O, carbon by C, and sodium by Na.
所有物质都由原子构成，原子是能参与化学反应的元素最小粒子。元素是由同一种原子组成的纯净物，每种元素都有自己的化学符号。例如，氧用 O 表示，碳用 C 表示，钠用 Na 表示。
Elements are listed on the periodic table, which organises them according to their properties. Some elements exist as individual atoms (like helium), but many exist as molecules of two or more atoms joined together, such as oxygen gas (O₂) and hydrogen gas (H₂).
元素列在元素周期表中，该表根据其性质进行编排。有些元素以单个原子的形式存在（如氦），但许多元素以两个或多个原子结合而成的分子形式存在，如氧气 (O₂) 和氢气 (H₂)。
When atoms of different elements join together chemically, they form compounds. A compound always contains two or more elements combined in a fixed proportion. For example, water (H₂O) is a compound made from hydrogen and oxygen atoms in a 2:1 ratio. The properties of a compound are usually very different from those of the elements that make it up.
当不同元素的原子以化学方式结合时，就形成了化合物。化合物总是由两种或多种元素以固定比例组成。例如，水 (H₂O) 是由氢原子和氧原子按 2:1 比例组成的化合物。化合物的性质通常与其构成元素的性质截然不同。
Chemical formulas use element symbols and subscript numbers to show the types and numbers of atoms in a substance. Carbon dioxide is CO₂, meaning one carbon atom and two oxygen atoms. A chemical reaction can be summarised with a word equation or a symbol equation, using an arrow (→) to mean ‘react to form’.
化学式使用元素符号和下角标数字来表示物质中原子的种类和数量。二氧化碳写作 CO₂，表示一个碳原子和两个氧原子。化学反应可以用文字方程式或符号方程式来总结，使用箭头 (→) 表示“反应生成”。
7. Mixtures and Separation Techniques | 混合物与分离技术
A mixture contains two or more different substances that are not chemically joined together. Because the substances keep their own properties, they can often be separated by physical methods. Air, seawater and sandy water are all examples of mixtures.
混合物含有两种或多种没有以化学方式结合的不同物质。由于各成分保持各自的性质，通常可以通过物理方法将它们分离。空气、海水和含沙的水都是混合物的例子。
Filtration is used to separate an insoluble solid from a liquid. The mixture is poured through filter paper in a funnel; the solid stays on the paper (residue) while the liquid passes through (filtrate). Evaporation and crystallisation can be used to obtain a soluble solid from a solution by removing the liquid, leaving the solid behind.
过滤用于将不溶性固体从液体中分离。混合物通过漏斗中的滤纸倒入；固体留在纸上（残渣），而液体透过滤纸（滤液）。蒸发和结晶可用于从溶液中获取可溶性固体，通过去除液体留下固体。
Simple distillation separates a solvent from a solution by boiling the mixture and then condensing the vapour back into a liquid. This is useful for obtaining pure water from salt water. Chromatography separates dissolved substances based on how they spread across a stationary phase, such as paper, and can be used to separate the colours in ink.
简单蒸馏通过将混合物煮沸，再将蒸气冷凝回液体，从而将溶剂从溶液中分离。这对于从盐水中获取纯水很有用。色谱法根据溶解的物质在固定相（如纸）上扩散的速度差异来分离它们，可用于分离墨水中的色素。
The ease of separation depends on the physical properties of the substances, such as boiling point, solubility and particle size. No new chemical substances are made during these separation processes; they are physical changes.
分离的难易取决于物质的物理性质，如沸点、溶解度和颗粒大小。在这些分离过程中没有产生新的化学物质；它们属于物理变化。
8. Acids and Alkalis | 酸与碱
Acids and alkalis are chemical opposites. An acid is a substance that releases hydrogen ions (H⁺) in water and has a pH less than 7. Common laboratory acids include hydrochloric acid, sulfuric acid and nitric acid. An alkali is a soluble base that releases hydroxide ions (OH⁻) in water and has a pH greater than 7. Examples include sodium hydroxide and potassium hydroxide.
酸和碱是化学上的对立物。酸是在水中释放氢离子 (H⁺) 且 pH 小于 7 的物质。常见的实验室酸包括盐酸、硫酸和硝酸。碱是可溶性碱，在水中释放氢氧根离子 (OH⁻) 且 pH 大于 7。例子包括氢氧化钠和氢氧化钾。
Indicators change colour depending on the pH of a solution. Litmus turns red in acid and blue in alkali. Universal indicator shows a range of colours from red (strong acid) to green (neutral, pH 7) to purple (strong alkali). The pH scale helps us compare the strengths of acids and alkalis.
指示剂根据溶液的 pH 改变颜色。石蕊在酸中变红，在碱中变蓝。通用指示剂显示从红色（强酸）到绿色（中性，pH 7）再到紫色（强碱）的颜色范围。pH 标度帮助我们比较酸碱的强度。
| Indicator | Colour in acid | Colour in neutral | Colour in alkali |
|---|---|---|---|
| Litmus | Red | Purple | Blue |
| Universal indicator | Red / orange / yellow | Green | Blue / purple |
When an acid reacts with an alkali, a neutralisation reaction occurs. The H⁺ ions from the acid react with the OH⁻ ions from the alkali to form water (H₂O). A salt is also produced; for example, hydrochloric acid + sodium hydroxide → sodium chloride + water. Neutralisation has many everyday uses, such as treating acidic soil with lime (an alkali) and using antacid tablets to relieve indigestion.
当酸与碱反应时，发生中和反应。酸中的 H⁺ 离子与碱中的 OH⁻ 离子反应生成水 (H₂O)。同时也生成一种盐；例如，盐酸 + 氢氧化钠 → 氯化钠 + 水。中和反应有许多日常用途，如用石灰（一种碱）处理酸性土壤，以及使用抗酸药片缓解消化不良。
9. Energy Transfers and Stores | 能量转移与储存
Energy is the ability to do work and is measured in joules (J). Energy can be stored in different ways. Common energy stores include kinetic energy (moving objects), thermal energy (hot objects), chemical energy (in food, fuels and batteries), gravitational potential energy (objects raised high), elastic potential energy (stretched or squashed objects) and nuclear energy (inside atoms).
能量是做功的能力，以焦耳 (J) 为单位。能量可以以不同方式储存。常见的能量储存包括动能（运动的物体）、热能（热的物体）、化学能（在食物、燃料和电池中）、重力势能（被举高的物体）、弹性势能（被拉伸或压缩的物体）和核能（原子内部）。
Energy can be transferred from one store to another, but it can never be created or destroyed. This is the principle of conservation of energy. Transfers can happen by heating, by forces doing work, by electric currents, or by radiation such as light and sound.
能量可以从一个储存转移到另一个储存，但绝不会被创造或消灭。这就是能量守恒原理。能量转移可以通过加热、力做功、电流或辐射（如光和声）等方式发生。
When we describe energy changes, we often use a simple energy transfer diagram. For example, when a battery-powered torch is switched on, chemical energy in the battery is transferred electrically to the bulb, where it is transferred into light and thermal energy. In a stretched rubber band, chemical energy in muscles is transferred mechanically into elastic potential energy; when released, that energy is transferred kinetically as the band flies through the air.
在描述能量变化时，我们经常使用简单的能量转移示意图。例如，当电池供电的手电筒打开时，电池中的化学能通过电流转移到灯泡，并在那里转化为光能和热能。在拉伸的橡皮筋中，肌肉中的化学能通过机械方式转移为弹性势能；释放时，该能量转化为动能，使橡皮筋飞过空中。
10. Forces and Motion | 力与运动
A force is a push or a pull, measured in newtons (N). Forces can change the speed, direction or shape of an object. When forces act on an object, they are often represented by arrows; the length of the arrow shows the magnitude (size) of the force, and the direction shows which way the force acts.
力是推或拉，以牛顿 (N) 为单位。力可以改变物体的速度、方向或形状。当力作用于物体上时，通常用箭头表示；箭头的长度表示力的大小，方向则表示力作用的方向。
When all forces on an object are balanced (equal and opposite), the object remains at rest or moves at a constant speed in a straight line. When forces are unbalanced, there is a resultant force that causes the object to accelerate (speed up), decelerate (slow down) or change direction.
当物体上的所有力平衡（大小相等方向相反）时，物体会保持静止或沿直线匀速运动。当力不平衡时，会产生一个合力，导致物体加速、减速或改变方向。
Speed is a measure of how fast an object moves and can be calculated using the relationship:
Speed = Distance ÷ Time
For instance, if a car travels 100 metres in 5 seconds, its speed is 20 m/s. Friction and air resistance are forces that oppose motion. They can be useful (allowing us to walk without slipping) but also unwanted, as they can waste energy and slow things down. Lubrication and streamlining reduce these opposing forces.
例如，如果一辆汽车在 5 秒内行驶了 100 米，其速度为 20 m/s。摩擦力和空气阻力是阻碍运动的力。它们可能是有益的（使我们行走时不滑倒），但也可能是有害的，因为它们浪费能量并使物体变慢。润滑和流线型设计可以减少这些阻力。
11. Electricity and Circuits | 电与电路
For an electrical current to flow, we need a circuit – a complete loop of conducting material. A simple circuit consists of a cell or battery (energy source), wires (conductors) and components such as bulbs, buzzers or motors. If there is a break in the circuit (an open switch or a gap), current stops flowing.
要使电流流动，我们需要一个电路——一个由导电材料构成的完整回路。一个简单电路由电池（能量源）、导线（导体）以及灯泡、蜂鸣器或电动机等元件组成。如果电路中有断点（断开的开关或间隙），电流就会停止流动。
Electric current is the flow of electric charge, usually carried by moving electrons in a metal wire. Components such as bulbs resist the flow and convert electrical energy into other forms. Conductors are materials that allow charge to flow easily (e.g., copper, silver), while insulators stop the flow (e.g., plastic, rubber, glass).
电流是电荷的流动，通常由金属导线中移动的电子携带。像灯泡这样的元件会阻碍流动，并将电能转化为其他形式的能量。导体是容易让电荷流动的材料（如铜、银），而绝缘体则阻碍流动（如塑料、橡胶、玻璃）。
In a series circuit, all the components are connected one after another in a single loop, so the same current flows through all of them. If one bulb breaks, the circuit is broken and all bulbs go out. In a parallel circuit, components are connected on separate branches, so each component gets the full battery voltage and if one branch fails, the others can still work. Understanding circuits helps us design safe and useful electrical devices.
在串联电路中，所有元件依次连接在一个回路中，因此流过各元件的电流相同。如果一个灯泡损坏，电路断开，所有灯泡都熄灭。在并联电路中，元件连接在独立的支路上，因此每个元件都获得电池的全电压，如果一条支路发生故障，其他支路仍可工作。理解电路有助于我们设计安全实用的电气设备。
12. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem is made up of all the living organisms in a particular area, interacting with each other and with their non-living environment. Key terms include habitat (the place where an organism lives), population (all the organisms of one species in that area) and community (all the populations of different species living together).
生态系统由特定区域内的所有生物体以及它们之间、与非生物环境之间的相互作用构成。关键术语包括栖息地（生物生活的地方）、种群（该区域内同一物种的所有个体）和群落（生活在一起的所有不同物种种群）。
Food chains show the feeding relationships between organisms. Arrows represent the direction of energy flow, from the food source to the eater. A simple food chain might start with a producer (a plant that makes its own food by photosynthesis), followed by a primary consumer (a herbivore that eats the plant), then a secondary consumer (a
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