📚 KS3 Edexcel Science: Core Knowledge Essentials | KS3 Edexcel 科学：核心知识点梳理
This article provides a comprehensive summary of the core knowledge required for the Edexcel Key Stage 3 Science curriculum. Covering biology, chemistry and physics, each section presents key concepts in paired English and Chinese explanations, helping bilingual learners strengthen their scientific understanding and revision.
本文全面梳理了 Edexcel 英国中学关键阶段三（KS3）科学课程的核心知识要点。内容涵盖生物、化学和物理，每个部分均以中英文配对讲解，帮助双语学习者夯实科学基础，高效备考。
1. Scientific Enquiry and Skills | 科学探究与技能
In KS3 Science, all investigations follow a structured approach. You must identify the independent variable (the one you change), the dependent variable (the one you measure) and the control variables (the ones you keep the same) to ensure a fair test.
在 KS3 科学中，所有探究都遵循结构化方法。你必须识别自变量（你改变的变量）、因变量（你测量的变量）以及控制变量（你保持不变的变量），以确保公平测试。
Data is recorded in tables with headings that include units, and results are often displayed using bar charts, line graphs or scatter graphs. When drawing a line graph, remember SLAP: Scale, Line, Axes, Plot.
数据记录在包含单位的表格中，结果通常用条形图、折线图或散点图呈现。绘制折线图时请记住 SLAP 原则：尺度、线条、坐标轴和描点。
Safety is paramount in the laboratory. Always wear goggles when heating substances or using chemicals, tie back long hair, and report any breakages immediately.
实验室安全至关重要。加热物质或使用化学品时务必佩戴护目镜，将长发束起，任何损坏应立即报告。
2. Cells and Life Processes | 细胞与生命过程
All living organisms carry out seven life processes, often remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.
所有生物都执行七大生命过程，常用首字母缩略词 MRS GREN 来记忆：运动、呼吸、感应、生长、繁殖、排泄和营养。
Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria. Plant cells have the same parts plus a rigid cell wall, a large permanent vacuole and chloroplasts for photosynthesis.
动物细胞含有细胞核、细胞质、细胞膜和线粒体。植物细胞除了含有这些部分外，还具有坚硬的细胞壁、大型永久液泡以及进行光合作用的叶绿体。
Substances move into and out of cells by diffusion, which is the net movement of particles from a region of high concentration to a region of low concentration. Osmosis is the diffusion of water across a partially permeable membrane.
物质通过扩散进出细胞，即微粒从高浓度区域净移动到低浓度区域。渗透是水通过部分透膜的扩散过程。
3. Human Organ Systems | 人体器官系统
The digestive system breaks down large insoluble food molecules into small soluble ones that can be absorbed into the blood. Digestion begins in the mouth and continues in the stomach and small intestine, with enzymes speeding up the process.
消化系统将大块不溶性食物分子分解为可溶性小分子，以便被血液吸收。消化从口腔开始，在胃和小肠中继续进行，酶加速了这一过程。
The respiratory system brings oxygen into the body and removes carbon dioxide. Gas exchange happens in the alveoli, tiny air sacs in the lungs with a large surface area and thin walls.
呼吸系统将氧气带入体内并排出二氧化碳。气体交换发生在肺泡中，肺泡是肺内的微小气囊，具有较大的表面积和薄壁。
The circulatory system transports oxygen, nutrients and waste products around the body. The heart pumps blood through arteries, capillaries and veins. Red blood cells contain haemoglobin, which binds to oxygen.
循环系统将氧气、营养物质和废物输送到全身。心脏将血液泵送入动脉、毛细血管和静脉。红细胞含有能与氧气结合的血红蛋白。
The skeleton provides support, protection and enables movement. Muscles work in antagonistic pairs, such as biceps and triceps, to move bones at joints.
骨骼提供支撑、保护作用并使运动成为可能。肌肉以拮抗成对的形式工作，如肱二头肌和肱三头肌，使骨骼在关节处运动。
4. Reproduction and Inheritance | 繁殖与遗传
Sexual reproduction involves the fusion of a male gamete (sperm) and a female gamete (egg) to form a zygote, which develops into an embryo. This produces offspring that are genetically different from the parents.
有性繁殖涉及雄性配子（精子）与雌性配子（卵子）融合形成受精卵，受精卵进一步发育为胚胎。这样产生的后代在遗传上不同于父母。
Asexual reproduction requires only one parent and produces identical offspring (clones). Examples include binary fission in bacteria and runners in strawberry plants.
无性繁殖只需要一个亲本，产生相同的后代（克隆）。例如细菌的分裂生殖和草莓的匍匐茎繁殖。
The nucleus of a cell contains chromosomes made of DNA. Genes are small sections of DNA that determine inherited characteristics. Humans have 23 pairs of chromosomes in most body cells.
细胞核含有由 DNA 构成的染色体。基因是决定遗传性状的 DNA 小片段。人类大部分体细胞含有 23 对染色体。
Variation among individuals can be caused by genetic factors, environmental factors, or a combination of both. Both continuous variation (e.g. height) and discontinuous variation (e.g. blood group) exist in populations.
个体间的变异可由遗传因素、环境因素或两者共同导致。种群中存在连续变异（如身高）和不连续变异（如血型）。
5. Particles and States of Matter | 粒子与物质状态
All substances are made of tiny particles. In solids, particles are closely packed in a regular arrangement and vibrate in fixed positions. In liquids, particles are close together but can move past each other. In gases, particles are far apart and move randomly at high speed.
所有物质都由微小粒子构成。固体中粒子紧密有规则地排列，并在固定位置上振动。液体中粒子紧密但能相互滑动。气体中粒子间隔很远并高速随机运动。
The particle model explains changes of state: melting, freezing, boiling, condensation and sublimation. During a state change, the temperature remains constant even though energy is still being transferred.
粒子模型解释了状态变化：熔化、凝固、沸腾、凝华和升华。在状态变化过程中，即使持续传递能量，温度也保持恒定。
Diffusion occurs fastest in gases because the particles have the most kinetic energy and move rapidly. An increase in temperature increases the rate of diffusion as particles gain more kinetic energy.
气体中扩散最快，因为其粒子动能最大且快速运动。温度升高会增加扩散速率，因为粒子获得了更多动能。
Gas pressure is caused by particles colliding with the walls of a container. Increasing the temperature or reducing the volume of the gas increases the pressure.
气体压强由粒子与容器壁碰撞产生。升高温度或减小气体体积会使压强增大。
6. Chemical Reactions and Acids/Bases | 化学反应与酸碱
In a chemical reaction, new substances are formed and the change is usually irreversible. Signs of a chemical change include a colour change, temperature change, gas production or precipitate formation.
在化学反应中，新物质生成且变化通常是不可逆的。化学变化的标志包括颜色变化、温度变化、产生气体或生成沉淀。
Chemical reactions can be represented by word equations or symbol equations. The total mass of reactants always equals the total mass of products; this is the law of conservation of mass.
化学反应可用文字方程式或符号方程式表示。反应物的总质量总是等于生成物的总质量，这就是质量守恒定律。
Acids have a pH value below 7 and release hydrogen ions (H⁺) in water. Alkalis have a pH above 7 and release hydroxide ions (OH⁻). The pH scale ranges from 0 to 14, with 7 being neutral.
酸的 pH 值小于 7，在水中释放氢离子（H⁺）。碱的 pH 值大于 7，释放氢氧根离子（OH⁻）。pH 值范围从 0 到 14，7 为中性。
In a neutralisation reaction, an acid reacts with an alkali to form a salt and water:
acid + alkali → salt + water
中和反应中，酸与碱反应生成盐和水：
酸 + 碱 → 盐 + 水
Common examples include hydrochloric acid with sodium hydroxide producing sodium chloride and water.
常见例子包括盐酸与氢氧化钠生成氯化钠和水。
7. Forces and Motion | 力与运动
A force is a push or a pull, measured in newtons (N). Forces can cause objects to start moving, speed up, slow down, change direction or change shape. Friction, gravity, air resistance and tension are examples of contact and non‑contact forces.
力是推或拉，以牛顿（N）为单位。力可以使物体开始运动、加速、减速、改变方向或改变形状。摩擦力、重力、空气阻力和张力都是接触力或非接触力的例子。
When forces on an object are balanced, its motion remains unchanged (steady speed or stationary). If the forces are unbalanced, the object will accelerate or decelerate in the direction of the resultant force.
当作用在物体上的力平衡时，其运动状态保持不变（匀速或静止）。如果力不平衡，物体将在合力方向上加速或减速。
Speed can be calculated using the relationship:
speed (m/s) = distance (m) ÷ time (s)
速度可以用以下关系式计算：
速度 (米/秒) = 距离 (米) ÷ 时间 (秒)
A distance–time graph can show an object’s motion. A straight, sloping line indicates constant speed; a horizontal line shows the object is stationary; a steeper gradient means greater speed.
距离‑时间图能展示物体的运动情况。倾斜直线表示恒定速度；水平线表示物体静止；斜率越大说明速度越快。
Gravity is a force that pulls objects towards the centre of the Earth. An object’s weight is the force due to gravity acting on its mass: weight (N) = mass (kg) × gravitational field strength (N/kg).
重力是将物体拉向地心的力。物体的重量是作用在其质量上的重力：重量 (N) = 质量 (kg) × 重力场强 (N/kg)。地球上重力场强约为 10 N/kg。
8. Energy and Electricity | 能量与电
Energy exists in many forms: thermal, kinetic, gravitational potential, chemical, elastic potential, nuclear and electromagnetic. Energy can be stored or transferred between stores, but it cannot be created or destroyed (conservation of energy).
能量有多种形式：热能、动能、重力势能、化学能、弹性势能、核能和电磁能。能量可以储存或在各能量库之间转移，但无法被创造或消灭（能量守恒定律）。
An electrical circuit requires a complete loop for current to flow. Current is the flow of electric charge, measured in amperes (A). Voltage (potential difference) is the push driving the current, measured in volts (V).
电路需要一个完整回路才能使电流流动。电流是电荷的流动，单位为安培（A）。电压（电势差）是驱动电流的推力，单位为伏特（V）。
Resistance opposes the flow of current and is measured in ohms (Ω). The relationship between voltage, current and resistance is given by Ohm’s law:
Voltage (V) = Current (A) × Resistance (Ω)
电阻阻碍电流流动，单位为欧姆（Ω）。电压、电流和电阻之间的关系由欧姆定律给出：
电压 (V) = 电流 (A) × 电阻 (Ω)
In a series circuit, components are connected end to end and the current is the same everywhere. In a parallel circuit, components are connected on separate branches and the current divides at junctions.
在串联电路中，元件首尾相连，各处电流相同。在并联电路中，元件连接在独立支路上，电流在节点处分流。
9. Waves and Radiation | 波及辐射
Waves transfer energy from one place to another without transferring matter. There are two main types: transverse waves (e.g. light, water waves) where the vibration is perpendicular to the direction of travel, and longitudinal waves (e.g. sound) where the vibration is parallel.
波将能量从一处传递到另一处而不传递物质。波主要有两类：横波（如光波、水波）的振动方向与传播方向垂直，纵波（如声波）的振动方向与传播方向平行。
Sound is produced by vibrating objects and travels as a longitudinal wave. It requires a medium (solid, liquid or gas) to travel and cannot travel through a vacuum. Loudness depends on amplitude, and pitch depends on frequency.
声音由振动物体产生，以纵波形式传播。声音需要介质（固体、液体或气体）才能传播，无法在真空中传播。响度取决于振幅，音调取决于频率。
Light travels in straight lines as a transverse wave at a speed of 300 000 occurs when light bounces off a smooth surface: angle of incidence = angle of reflection.
光在真空中以横波形式沿直线传播，速度为 300 000 000 米/秒。当光从光滑表面弹回时发生反射：入射角等于反射角。
Refraction happens when light passes from one transparent medium to another and changes speed, causing a change in direction. White light can be dispersed by a prism into the visible spectrum: red, orange, yellow, green, blue, indigo and violet.
当光从一种透明介质进入另一种介质时，速度改变导致方向改变，发生折射。白光可通过棱镜色散成可见光谱：红、橙、黄、绿、蓝、靛、紫。
10. Earth and Space | 地球与宇宙
The Earth consists of three main layers: the crust (thin, solid outer layer), the mantle (thick layer of semi‑molten rock) and the core (made of iron and nickel, with a solid inner core and liquid outer core).
地球由三个主要层构成：地壳（薄而坚实的外层）、地幔（半熔融岩石的厚层）和地核（由铁和镍组成，内核为固态，外核为液态）。
Rocks are classified into three types: igneous (formed from cooled magma or lava), sedimentary (formed from compressed layers of sediment) and metamorphic (formed when existing rocks are changed by heat and pressure). The rock cycle shows how rocks change over time.
岩石分为三类：火成岩（由岩浆或熔岩冷却形成）、沉积岩（由沉积物被压缩成层形成）和变质岩（原有岩石在热和压力下改变形成）。岩石循环展示了岩石如何随时间变化。
The Earth orbits the Sun, which is the centre of our solar system. The eight planets in order from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Gravity keeps planets in their orbits.
地球绕太阳公转，太阳是太阳系的中心。八大行星距太阳由近到远依次为：水星、金星、地球、火星、木星、土星、天王星和海王星。引力使行星保持在轨道上运行。
The Moon orbits the Earth roughly every 28 days. The phases of the Moon—new, crescent, quarter, gibbous and full—occur because we see different amounts of the lit half of the Moon as it orbits.
月球大约每 28 天绕地球一周。月相（新月、蛾眉月、上／下弦月、凸月和满月）的变化是由于月球公转时我们看到的被照亮半面的面积不同。
Stars form from clouds of gas and dust and undergo a life cycle. Our Sun is a main sequence star. Understanding the seasons, eclipses and the role of the Earth’s tilted axis completes the picture of KS3 Space science.
恒星由气体和尘埃云形成，并经历生命周期。我们的太阳是一颗主序星。理解季节、日食和月食以及地球倾斜轴的作用，构成了 KS3 太空科学的完整图景。
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