📚 Year 9 WJEC Science: Core Knowledge Consolidation | WJEC九年级科学：核心知识点梳理
Welcome to your comprehensive revision guide for Year 9 WJEC Science. This article brings together the most important concepts across biology, chemistry and physics, presented in clear bilingual pairs to support your learning. By revisiting these core topics, you will strengthen your understanding of how living organisms function, how matter is structured and transformed, and how energy and forces shape the world around us. Use this resource to consolidate key knowledge, practise recall and build confidence for assessments.
欢迎来到九年级 WJEC 科学综合复习指南。本文汇总了生物、化学和物理学科中最重要的概念，以清晰的中英对照形式呈现，帮助您巩固学习。通过重温这些核心主题，您将加深对生物体功能、物质结构与变化以及能量和力如何塑造世界的理解。请利用这份资料梳理核心知识、练习回忆并为测评建立信心。
1. Cells and Microscopy | 细胞与显微技术
All living organisms are made of cells. Cells are classified as prokaryotic (lacking a nucleus, e.g. bacteria) or eukaryotic (with a nucleus, e.g. animal and plant cells).
所有生物体都由细胞构成。细胞分为原核细胞（无细胞核，如细菌）和真核细胞（有细胞核，如动物和植物细胞）。
Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells have these plus a rigid cell wall, chloroplasts and a large permanent vacuole.
动物细胞包含细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞除了这些，还有坚硬的细胞壁、叶绿体和一个大而永久的液泡。
Microscopes magnify tiny objects. Total magnification is calculated by multiplying the eyepiece lens power and the objective lens power.
显微镜可放大微小物体。总放大倍数是目镜放大倍数与物镜放大倍数的乘积。
Total Magnification = Eyepiece magnification × Objective magnification
总放大倍数 = 目镜放大倍数 × 物镜放大倍数
To view a specimen clearly under a light microscope, a thin sample is placed on a slide, often stained to make structures more visible.
为了在光学显微镜下清晰地观察标本，需将薄样品放在载玻片上，通常进行染色以使结构更明显。
Resolution is the ability to distinguish two close points as separate. Electron microscopes have much higher resolution than light microscopes.
分辨率是指区分两个相近点的能力。电子显微镜的分辨率远高于光学显微镜。
2. Digestive System and Enzymes | 消化系统与酶
The digestive system breaks down large food molecules into smaller, soluble ones that can be absorbed into the bloodstream. Organs include the mouth, oesophagus, stomach, small intestine, large intestine and liver.
消化系统将大食物分子分解成可被吸收进入血液的小而可溶的分子。器官包括口腔、食道、胃、小肠、大肠和肝脏。
Enzymes are biological catalysts that speed up chemical reactions without being used up. They have active sites with specific shapes that fit their substrates in the lock-and-key model.
酶是生物催化剂，能加速化学反应而自身不被消耗。酶具有活性位点，其特定形状与底物相匹配，遵循锁钥模型。
Amylase breaks down starch into maltose, protease digests proteins into amino acids, and lipase breaks lipids into fatty acids and glycerol.
淀粉酶将淀粉分解为麦芽糖，蛋白酶将蛋白质消化为氨基酸，脂肪酶将脂类分解为脂肪酸和甘油。
| Enzyme | Substrate | Products |
|---|---|---|
| Amylase | Starch | Maltose |
| Protease | Protein | Amino acids |
| Lipase | Lipids | Fatty acids & glycerol |
The optimum temperature for human enzymes is around 37°C, while pH optima vary: stomach proteases work best in acidic conditions, whereas intestinal enzymes prefer alkaline environments.
人体酶的最适温度约为37°C，而最适pH值各有不同：胃蛋白酶在酸性条件下作用最佳，而肠道酶则偏好碱性环境。
Bile, produced by the liver, emulsifies fats and neutralises stomach acid, creating ideal conditions for small-intestine enzymes.
胆汁由肝脏产生，能乳化脂肪并中和胃酸，为小肠酶创造理想条件。
3. Breathing and Circulation | 呼吸与循环系统
The respiratory system exchanges gases. Air enters through the trachea, bronchi and bronchioles before reaching the alveoli, where oxygen diffuses into the blood and carbon dioxide diffuses out.
呼吸系统进行气体交换。空气通过气管、支气管和细支气管进入，最终到达肺泡，在此氧气扩散入血，二氧化碳扩散出血液。
The heart is a double pump; the right side pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the body. The four chambers are the right atrium, right ventricle, left atrium and left ventricle.
心脏是双泵；右侧将缺氧血泵至肺部，左侧将富氧血泵至全身。四个腔室为右心房、右心室、左心房和左心室。
Arteries carry blood away from the heart under high pressure; veins return blood to the heart and contain valves; capillaries are tiny, thin-walled vessels where exchange takes place.
动脉将血液在高压下带离心脏；静脉将血液送回心脏并含有瓣膜；毛细血管是进行物质交换的微小薄壁血管。
Heart rate can increase during exercise to deliver more oxygen and glucose to muscles. Respiration releases energy: aerobic respiration requires oxygen, while anaerobic respiration does not.
运动时心率会增加，为肌肉输送更多氧气和葡萄糖。呼吸作用释放能量：有氧呼吸需要氧气，而无氧呼吸则不需要。
Aerobic: glucose + oxygen → carbon dioxide + water (+ energy)
有氧呼吸：葡萄糖 + 氧气 → 二氧化碳 + 水 （+ 能量）
4. Atoms, Elements and Compounds | 原子、元素与化合物
An atom is the smallest unit of an element that retains chemical properties. It consists of protons (+), neutrons (0) and electrons (–). The nucleus contains protons and neutrons.
原子是保留元素化学性质的最小单位。它由质子（+）、中子（0）和电子（–）组成。原子核包含质子和中子。
he mass number is the sum of protons and neutrons. In a neutral atom, electrons = protons.
原子序数是质子的数目；质量数是质子与中子之和。在电中性原子中，电子数等于质子数。
An element is made of one type of atom. A compound is two or more different elements chemically bonded together, such as H₂O or CO₂.
元素由一种原子组成。化合物是由两种或多种不同元素通过化学键结合而成，例如 H₂O 或 CO₂。
Chemical formulas show the types and numbers of atoms. A mixture contains different substances that are not chemically combined and can be separated by physical techniques.
化学式表示原子的种类和数目。混合物含有不同物质，它们未经过化学结合，可以通过物理方法分离。
Simple separation methods include filtration, evaporation, distillation and chromatography.
简单的分离方法包括过滤、蒸发、蒸馏和色谱法。
5. The Periodic Table | 元素周期表
The periodic table arranges elements in order of increasing atomic number. The horizontal rows are called periods; the vertical columns are called groups.
元素周期表按原子序数递增的顺序排列元素。横行称为周期；纵列称为族。
Group 1 metals (alkali metals) are soft, very reactive and react vigorously with water to produce hydrogen gas and alkaline hydroxides.
第1族金属（碱金属）质地软、非常活泼，与水剧烈反应生成氢气和碱性氢氧化物。
Group 7 elements (halogens) are toxic non-metals. Their reactivity decreases down the group: fluorine is the most reactive, iodine the least.
第7族元素（卤素）是有毒的非金属。它们的反应性沿族向下递减：氟最活泼，碘最不活泼。
Group 0 (noble gases) are inert, colourless gases because their outer electron shells are full, making them stable.
第0族（稀有气体）是惰性、无色气体，因为其最外电子层已满，结构稳定。
Metals are found on the left and centre; non-metals on the right. Transition metals in the central block are typical metals: hard, shiny and good conductors.
金属位于左侧和中部；非金属位于右侧。中间的过渡金属是典型金属：坚硬、有光泽且是优良导体。
6. Bonding and Structure | 化学键与结构
Ionic bonding involves the transfer of electrons from a metal to a non-metal, forming positive and negative ions that attract each other. Sodium chloride (NaCl) has a giant ionic lattice.
离子键涉及电子从金属转移到非金属，形成相互吸引的正负离子。氯化钠（NaCl）具有巨型离子晶格。
Covalent bonding occurs when non-metal atoms share pairs of electrons to achieve full outer shells. Simple molecular substances like H₂O and CO₂ have low melting points.
共价键发生在非金属原子共用电子对以达到满壳层时。像H₂O和CO₂这样的简单分子物质具有低熔点。
Metallic bonding consists of positive metal ions surrounded by a 'sea' of delocalised electrons. This explains why metals conduct electricity and can be bent.
金属键由正金属离子和周围的离域电子“海洋”构成。这解释了金属为何导电且可弯曲。
Diamond and graphite are both carbon allotropes. Diamond is very hard with each carbon bonded to four others; graphite has layers that can slide, making it slippery and conductive.
金刚石和石墨都是碳的同素异形体。金刚石非常坚硬，每个碳原子与周围四个碳原子键合；石墨具有可滑动的层状结构，使其润滑且导电。
7. Chemical Reactions and Acids & Alkalis | 化学反应与酸碱
A chemical change produces new substances, often showing signs such as fizzing, colour change or a temperature change. The total mass remains the same – the law of conservation of mass.
化学变化产生新物质，常有冒泡、颜色变化或温度变化等迹象。总质量保持不变——质量守恒定律。
Acids have a pH below 7; alkalis have a pH above 7. A neutral solution has a pH of 7. Universal indicator or pH meters can measure pH.
酸的pH值低于7；碱的pH值高于7。中性溶液的pH值为7。通用指示剂或pH计可用于测量pH。
Acids contain hydrogen ions (H⁺) in water; alkalis contain hydroxide ions (OH⁻). Neutralisation is the reaction between H⁺ and OH⁻ to form water.
酸在水中含有氢离子（H⁺）；碱含有氢氧根离子（OH⁻）。中和反应是H⁺与OH⁻反应生成水。
acid + alkali → salt + water
酸 + 碱 → 盐 + 水
Metal oxides and metal hydroxides are bases. Common salts include sodium chloride, copper sulfate and potassium nitrate. Crystallisation can be used to obtain pure salt crystals.
金属氧化物和金属氢氧化物是碱。常见的盐包括氯化钠、硫酸铜和硝酸钾。结晶法可用于获得纯盐晶体。
8. Energy and Energy Transfers | 能量与能量传递
Energy exists in different stores: kinetic, chemical, thermal, gravitational potential, elastic potential, nuclear and magnetic. Energy is conserved – it cannot be created or destroyed, only transferred.
能量以不同形式储存：动能、化学能、热能、重力势能、弹性势能、核能和磁能。能量守恒——它不能被创造或消灭，只能被转移。
Work is done when a force moves an object. The amount of work done equals the energy transferred.
力使物体移动时做功。做功的多少等于转移的能量。
Work done = force × distance (W = F × d)
做功 = 力 × 距离 （W = F × d）
Thermal energy can be transferred by conduction (through solids), convection (in fluids) or radiation (infrared waves through a vacuum). Insulators reduce unwanted heat transfer.
热能可以通过传导（固体）、对流（流体）或辐射（通过真空的红外波）传递。绝缘体可减少不必要热传递。
Power is the rate of energy transfer. A more powerful appliance transfers more energy each second.
Power = energy transferred ÷ time (P = E ÷ t)
功率 = 转移的能量 ÷ 时间 （P = E ÷ t）
9. Forces and Motion | 力与运动
Forces are pushes or pulls, measured in newtons (N). They can change an object's speed, shape or direction. Common forces include weight, friction, tension, air resistance and upthrust.
力是推或拉，以牛顿（N）为单位。力可以改变物体的速度、形状或方向。常见力包括重力、摩擦力、张力、空气阻力和浮力。
here g = 10 N/kg on Earth. Mass is the amount of matter and does not change with location.
重量是重力作用下的力：W = m × g，地球上g = 10 N/kg。质量是物质的量，不随位置改变。
Balanced forces keep an object at rest or at constant speed; unbalanced forces cause acceleration or deceleration.
平衡力使物体保持静止或匀速运动；不平衡力导致加速或减速。
Speed can be calculated from distance–time graphs. The gradient of a distance–time graph represents speed.
Average speed = total distance ÷ total time
平均速度 = 总距离 ÷ 总时间
Friction opposes motion and can turn kinetic energy into thermal energy. Lubrication reduces friction.
摩擦力阻碍运动，可将动能转化为热能。润滑可减少摩擦。
10. Electricity and Circuits | 电与电路
Current is the flow of electric charge, measured in amperes (A). In a single, closed loop, the current is the same everywhere. An ammeter is connected in series to measure current.
电流是电荷的流动，以安培（A）为单位。在单一的闭合回路中，各处电流相同。电流表串联接入以测量电流。
Potential difference (voltage) is the energy transferred per coulomb of charge, measured in volts (V). It is measured with a voltmeter connected in parallel.
电势差（电压）是每库仑电荷转移的能量，以伏特（V）为单位。用电压表并联测量。
Resistance limits the flow of current. Ohm's law relates these three quantities:
V = I × R
电压 = 电流 × 电阻 （V = I × R）
In a series circuit, total resistance increases as more resistors are added: Rtotal . . In parallel circuits, total resistance decreases because multiple paths are available.
在串联电路中，增加电阻会导致总电阻增大：R_总 = R₁ + R₂ + …。在并联电路中，由于存在多条路径，总电阻减小。
Conductors (e.g. metals) have low resistance; insulators (e.g. plastic) have very high resistance. Components like diodes and LDRs have non-linear I–V characteristics.
导体（如金属）电阻低；绝缘体（如塑料）电阻非常高。二极管和光敏电阻等元件的电流-电压特性是非线性的。
Mains electricity is alternating current (a.c.) at 230 V in the UK. Safety features include fuses and earth wires.
市电在英国为230V交流电（a.c.）。安全装置包括保险丝和接地线。
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