📚 Year 8 Edexcel Science: Core Knowledge Summary | 核心知识点梳理
Welcome to your Year 8 Edexcel Science revision guide. This article pulls together the essential knowledge across Biology, Chemistry and Physics that you will need for your assessments. From the building blocks of life to the forces that shape motion, each section is broken down into clear, paired explanations in English and Chinese. Use this resource to check your understanding, fill gaps, and build confidence before your tests.
欢迎来到 Year 8 Edexcel 科学复习指南。本文汇集了生物学、化学和物理学中你将要评估的核心知识。从生命的组成单元到塑造运动的力，每个部分都用清晰的中英双语解释进行拆解。利用这份资料来检查你的理解、填补知识空白，并在考试前建立信心。
1. Cells and Organisation | 细胞与组织
All living organisms are made of cells. Animal and plant cells share common structures: a nucleus that controls the cell's activities, cytoplasm where chemical reactions occur, a cell membrane that controls what enters and leaves, mitochondria for energy release through respiration, and ribosomes for protein synthesis. However, plant cells have three additional features: a rigid cell wall made of cellulose for support, chloroplasts containing chlorophyll for photosynthesis, and a large permanent vacuole filled with cell sap that helps maintain turgor pressure.
所有生物体都由细胞构成。动物和植物细胞具有共同的结构：控制细胞活动的细胞核、发生化学反应的细胞质、控制物质进出的细胞膜、通过呼吸作用释放能量的线粒体，以及合成蛋白质的核糖体。但植物细胞还有三个额外的特征：由纤维素构成的坚硬细胞壁起支撑作用，含有叶绿素的叶绿体用于光合作用，还有一个充满细胞液的大液泡帮助维持膨压。
Cells are organised into tissues, organs and organ systems. A tissue is a group of similar cells working together, such as muscle tissue. An organ is made of different tissues working together, like the heart or a leaf. Organ systems are groups of organs that perform a major function; for example, the digestive system includes the stomach, intestines and liver. This hierarchical organisation allows multicellular organisms to carry out complex life processes efficiently.
细胞组织成组织、器官和器官系统。组织是一群相似细胞协同工作的集合，例如肌肉组织。器官由不同组织协同工作构成，如心脏或叶片。器官系统是执行主要功能的器官群；例如，消化系统包括胃、肠和肝脏。这种层级化的组织使得多细胞生物能够高效地执行复杂的生命过程。
2. Nutrition and Digestion | 营养与消化
A balanced diet provides seven essential nutrients. Carbohydrates and fats supply energy; proteins are needed for growth and repair; vitamins and minerals keep the body functioning in small amounts; water acts as a solvent and transport medium; and dietary fibre aids digestion by preventing constipation. Starchy foods like bread are rich in carbohydrates, while meat and beans are good protein sources. Not consuming enough of a nutrient can lead to deficiency diseases, such as scurvy from a lack of vitamin C.
均衡的膳食提供七种必需的营养素。碳水化合物和脂肪提供能量；蛋白质是生长和修复所需；维生素和矿物质少量即可维持身体机能；水作为溶剂和运输介质；膳食纤维通过预防便秘帮助消化。像面包这类淀粉食物富含碳水化合物，而肉类和豆类则是良好的蛋白质来源。摄入某种营养素不足会导致缺乏症，例如缺少维生素C会引起坏血病。
Digestion breaks down large, insoluble food molecules into small, soluble molecules that can be absorbed into the blood. The journey begins in the mouth, where chewing increases surface area and salivary amylase starts breaking down starch. In the stomach, acid kills bacteria and protease enzymes begin protein digestion. In the small intestine, enzymes from the pancreas and bile from the liver complete digestion; the small intestine also absorbs the soluble products through its large surface area created by villi.
消化将大的、不可溶的食物分子分解成小的、可溶的分子从而被血液吸收。这一旅程从口腔开始，咀嚼增加表面积，唾液淀粉酶开始分解淀粉。在胃中，胃酸杀灭细菌，蛋白酶开始消化蛋白质。在小肠中，来自胰腺的酶和来自肝脏的胆汁完成消化；小肠还通过绒毛形成的大面积表面吸吸收可溶性产物。
3. Breathing and Respiration | 呼吸与呼吸作用
Breathing is the physical process of moving air into and out of the lungs. Air travels through the trachea, bronchi and bronchioles before reaching the alveoli—tiny air sacs surrounded by capillaries. Oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli to be exhaled. The diaphragm and intercostal muscles change the chest cavity volume, causing inhalation and exhalation.
呼吸是空气进出肺的物理过程。空气经过气管、支气管和细支气管，最终到达肺泡——被毛细血管包围的微小气囊。氧气从肺泡扩散到血液中，同时二氧化碳从血液扩散到肺泡中被呼出。膈肌和肋间肌改变胸腔容积，引起吸气和呼气。
Cellular respiration is a chemical process that releases energy from glucose. Aerobic respiration uses oxygen and produces carbon dioxide and water, along with a large amount of energy. The summary is often written as: glucose + oxygen → carbon dioxide + water (+ energy). Anaerobic respiration occurs without oxygen and releases much less energy, producing lactic acid in animals or ethanol and carbon dioxide in yeast. Understanding the difference between breathing and respiration is crucial: one is ventilation, the other is a cellular reaction.
细胞呼吸是从葡萄糖中释放能量的化学过程。有氧呼吸使用氧气，产生二氧化碳、水和大量能量。其总结常写作：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。无氧呼吸在无氧时发生，释放的能量少得多，在动物体内产生乳酸，在酵母中产生乙醇和二氧化碳。理解呼吸（换气）与呼吸作用（细胞反应）的区别至关重要。
4. Reproduction | 生殖
In humans, reproduction involves the fusion of a sperm and an egg. The male reproductive system produces sperm in the testes and delivers it through the sperm duct; the female system releases eggs from ovaries and nurtures a developing embryo in the uterus. Fertilisation occurs when a sperm nucleus fuses with an egg nucleus in the oviduct, forming a zygote that implants into the uterus lining and develops into an embryo, protected by amniotic fluid and receiving nutrients via the placenta.
在人类中，生殖涉及精子和卵子的融合。男性生殖系统在睾丸中产生精子并通过输精管输送；女性系统从卵巢释放卵子，并在子宫中孕育发育中的胚胎。当精子核与卵子核在输卵管中融合时发生受精，形成受精卵，将其植入子宫内膜并发育成胚胎，胚胎受羊水保护并通过胎盘获取营养。
Flowering plants also reproduce sexually. The stamen (male part) produces pollen grains containing male gametes, while the carpel (female part) contains ovules. Pollination transfers pollen from an anther to a stigma; pollen tubes then grow down the style to deliver male nuclei to the ovules. After fertilisation, the ovule develops into a seed and the ovary becomes a fruit. Seed dispersal methods—wind, water, animals or explosion—help plants colonise new areas.
开花植物也进行有性生殖。雄蕊（雄性部分）产生含有雄配子的花粉粒，而雌蕊（雌性部分）含有胚珠。传粉将花粉从花药转移到柱头；随后花粉管沿花柱向下生长，将雄核送入胚珠。受精后，胚珠发育成种子，子房发育成果实。种子传播方式——风、水、动物或弹射——帮助植物拓殖新的区域。
5. Atoms, Elements and Compounds | 原子、元素与化合物
Everything is made of atoms, each consisting of a nucleus containing protons and neutrons, surrounded by electrons arranged in shells. The atomic number tells you the number of protons, and the mass number is the sum of protons and neutrons. Atoms are neutral because the number of electrons equals the number of protons. Isotopes are atoms of the same element with different numbers of neutrons.
万物由原子构成，每个原子包含一个由质子和中子组成的原子核，核外电子按壳层排列。原子序数表示质子数，质量数是质子数与中子数之和。原子是电中性的，因为电子数等于质子数。同位素是同一元素中中子数不同的原子。
An element is a substance made of only one type of atom; the periodic table organises elements by increasing atomic number. Metals are on the left, non-metals on the right. Compounds form when elements chemically combine in fixed ratios. Ionic compounds involve transfer of electrons, such as sodium chloride (NaCl), while covalent compounds involve sharing of electron pairs, like water (H₂O) and carbon dioxide (CO₂). Simple chemical formulae show the types and ratios of atoms.
元素是只由一种原子组成的物质；元素周期表按原子序数递增排列。金属在左侧，非金属在右侧。当元素以固定比例化学结合时形成化合物。离子化合物涉及电子转移，如氯化钠 (NaCl)，而共价化合物涉及电子对共用，如水 (H₂O) 和二氧化碳 (CO₂)。简单的化学式表示原子的种类和比例。
6. Chemical Reactions | 化学反应
temperature change (exothermic or endothermic), gas production (bubbles or effervescence), and formation of a precipitate in a solution. Combustion reactions with oxygen usually release heat and light, while thermal decomposition breaks down a compound using heat, such as calcium carbonate → calcium oxide + carbon dioxide.
化学反应生成新物质，涉及反应物转变为产物。发生反应的迹象包括颜色变化、温度变化（放热或吸热）、气体产生（气泡或冒泡），以及溶液中生成沉淀。与氧气的燃烧反应通常释放热和光，而热分解利用热量将化合物分解，例如碳酸钙 → 氧化钙 + 二氧化碳。
ds contain hydrogen ions (H⁺) and alkalis contain hydroxide ions (OH⁻). A neutralisation reaction between an acid and an alkali produces a salt and water: hydrochloric acid + sodium hydroxide → sodium chloride + water. Indicators like litmus change colour in acids and alkalis, helping identify them.
酸和碱是重要的化学类别。pH标度从0（强酸性）到14（强碱性），7为中性。酸含有氢离子 (H⁺)，碱含有氢氧根离子 (OH⁻)。酸与碱之间的中和反应生成盐和水：盐酸 + 氢氧化钠 → 氯化钠 + 水。石蕊等指示剂在酸和碱中改变颜色，帮助鉴别它们。
7. Forces and Motion | 力与运动
Forces are pushes or pulls that can change an object' e.g. gravity, magnetism, electrostatic force). Balanced forces produce no change in motion— ue to gravity, calculated as mass × gravitational field strength (about 10 N/kg on Earth).
力是推或拉，可以改变物体的速度、方向或形状。接触力需要触碰（如摩擦力、张力），而非接触力可隔空作用（如重力、磁力、静电力）。平衡的力不改变运动状态——物体保持静止或匀速运动。不平衡的力会导致加速或减速。重量是由于重力产生的力，计算公式为质量 × 重力场强（地球约 10 牛/千克）。
Speed can be calculated using the relationship: speed = distance ÷ time. A distance-time graph shows how far an object has travelled over time; a straight diagonal line represents constant speed, a horizontal line indicates the object is stationary, and a steeper slope means a higher speed. Friction and air resistance often oppose motion, causing objects to slow down unless a driving force overcomes them.
速度可使用关系式计算：速度 = 距离 ÷ 时间。距离 - 时间图显示物体随时间移动的距离；倾斜直线代表匀速，水平线表示物体静止，斜率越陡代表速度越快。摩擦力和空气阻力常会阻碍运动，除非驱动力克服了它们，否则物体会变慢。
8. Energy | 能量
Energy exists in many forms: kinetic (movement), thermal (heat), light, sound, electrical, chemical, gravitational potential, elastic potential and nuclear. Energy cannot be created or destroyed—only transferred, stored or dissipated. Energy stores include kinetic energy, thermal energy and chemical energy. During an event like a ball rolling down a ramp, gravitational potential energy is transferred to kinetic energy, and some energy is dissipated as thermal energy due to friction.
能量以许多形式存在：动能（运动）、热能（热）、光能、声能、电能、化学能、重力势能、弹性势能和核能。能量既不能创造也不能消灭——只能转移、储存或耗散。能量储存包括动能、热能和化学能。在球沿斜坡滚下的事件中，重力势能转化为动能，由于摩擦，部分能量以热能形式耗散。
Energy resources are classified as renewable and non-renewable. Fossil fuels (coal, oil, natural gas) and nuclear fuels are non-renewable; they will run out and often produce carbon dioxide or radioactive waste. Renewable resources include solar, wind, wave, tidal, hydroelectric power, geothermal and biomass. Heat can be transferred by conduction (mainly in solids), convection (in fluids), and radiation (via infrared waves, which can travel through a vacuum). Insulation reduces unwanted energy transfers.
能源分为可再生与不可再生。化石燃料（煤、石油、天然气）和核燃料是不可再生的；它们终将耗尽，且常产生二氧化碳或放射性废物。可再生资源包括太阳能、风能、波浪能、潮汐能、水力发电、地热和生物质。热能可通过传导（主要在固体中）、对流（在流体中）和辐射（通过红外波，可在真空中传播）传递。隔热可以减少不必要的能量转移。
9. Electricity | 电
An electric current is a flow of electrical charge, usually carried by electrons in a metal wire. For current to flow, a complete circuit is needed with a source of potential difference, such as a cell or battery. Current is measured in amperes (A) using an ammeter connected in series. Potential difference (voltage) is measured in volts (V) using a voltmeter connected in parallel across a component; it indicates the energy transferred per unit charge.
电流是电荷的流动，通常由金属线中的电子携带。要使电流动，需要一个完整的电路以及电势差的来源，例如电池。电流用安培 (A) 为单位，使用串联在电路中的安培表测量。电势差（电压）以伏特 (V) 为单位，使用并联在元件两端的伏特表测量；它表示每单位电荷转移的能量。
Circuit components behave differently. A resistor limits the flow of current; the more resistance, the smaller the current for a given potential difference. In a series circuit, the current is the same everywhere, but the potential difference is shared across components. In a parallel circuit, the current splits and recombines at junctions, while each branch has the same potential difference as the battery. Switches, lamps, buzzers and motors are common components drawn with standard circuit symbols.
电路元件的行为各不相同。电阻器限制电流流动；在给定电势差下，电阻越大，电流越小。在串联电路中，各处电流相同，但电势差在各元件间分配。在并联电路中，电流在节点处分流并重新汇合，而每条支路的电势差与电池相同。开关、灯泡、蜂鸣器和马达是常见元件，用标准电路符号绘制。
10. Waves: Sound and Light | 波：声与光
Sound is produced by vibrations and travels as longitudinal waves through a medium (solid, liquid or gas) by causing compressions and rarefactions. Sound cannot travel through a vacuum. The frequency of a sound wave determines its pitch—higher frequency gives a higher pitch. The amplitude relates to the loudness; a larger amplitude produces a louder sound. The human ear collects sound waves, causing the eardrum to vibrate, which transmits vibrations through small bones to the cochlea.
声音由振动产生，以纵波形式通过介质（固体、液体或气体）传播，引起压缩和稀疏。声音不能在真空中传播。声波的频率决定音高——频率越高，音调越高。振幅与响度相关；振幅越大，声音越响。人耳收集声波，引起鼓膜振动，振动通过小骨传至耳蜗。
Light travels as transverse waves and can move through a vacuum. The law of reflection states that the angle of incidence equals the angle of reflection, measured from the normal. Refraction occurs when light passes between media of different densities, changing speed and direction unless entering along the normal. White light can be dispersed by a prism into the colours of the visible spectrum: red, orange, yellow, green, blue, indigo and violet. Coloured objects reflect only certain wavelengths, absorbing the rest.
光以横波传播，可以在真空中行进。反射定律指出，入射角等于反射角，均从法线量起。折射发生在光在不同密度的介质间穿过时，除非沿法线入射，否则速度和方向均会改变。白光可通过棱镜色散为可见光谱的颜色：红、橙、黄、绿、蓝、靛、紫。有色物体只反射特定波长，吸收其余部分。
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