📚 Exploring Science 740: Core Principles for IGCSE Edexcel | 探索科学740：IGCSE Edexcel核心原理
This article provides a comprehensive overview of the foundational concepts in IGCSE Edexcel Science, covering key ideas from biology, chemistry, and physics. We will explore the scientific method, the nature of living and non-living matter, and the fundamental laws that govern energy and motion. Mastering these core principles will build your confidence for the exams and deepen your appreciation of how science explains the world around us.
本文全面概述IGCSE Edexcel科学的基础概念，涵盖生物学、化学和物理学的核心思想。我们将探讨科学方法、生命与非生命物质的本质，以及支配能量与运动的基本定律。掌握这些核心原理将增强你应对考试的信心，并加深你对科学如何解释周围世界的理解。
1. The Scientific Method | 科学方法
Science is a systematic way of investigating natural phenomena. It begins with making observations and asking questions. From these, a hypothesis — a testable statement — is formed. A good hypothesis can be supported or refuted through controlled experiments, where variables are carefully managed.
科学是研究自然现象的系统方法。它始于观察和提出问题。由此形成假设——一个可验证的陈述。一个好的假设可以通过控制实验来支持或反驳，实验中的变量需小心管理。
In an experiment, the independent variable is the one you deliberately change, the dependent variable is what you measure, and control variables are kept constant to ensure a fair test. Repeated trials increase reliability, and presenting data in graphs often helps to identify trends or anomalies. Peer review is a vital step before results become accepted scientific knowledge.
在实验中，自变量是你有意改变的变量，因变量是你测量的变量，控制变量则保持不变以确保公平测试。重复实验可提高可靠性，用图表呈现数据往往有助于识别趋势或异常。在结果被接受为科学知识之前，同行评审是至关重要的一步。
2. Cells – The Building Blocks of Life | 细胞——生命的基石
All living organisms are composed of cells. The IGCSE syllabus distinguishes between prokaryotic cells (e.g., bacteria, which lack a nucleus) and eukaryotic cells (plants, animals, fungi), which have a distinct nucleus containing DNA. Key structures in animal cells include the cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes.
所有生物体都由细胞构成。IGCSE教学大纲区分原核细胞（如细菌，无细胞核）和真核细胞（植物、动物、真菌），后者含有储存DNA的明确细胞核。动物细胞的关键结构包括细胞膜、细胞质、细胞核、线粒体和核糖体。
Plant cells share these organelles but also contain a rigid cell wall made of cellulose, a large permanent vacuole for sap storage, and chloroplasts where photosynthesis occurs. Specialised cells, such as red blood cells (no nucleus, biconcave shape for more oxygen) and root hair cells (long extension for water absorption), are adapted to carry out specific functions efficiently.
植物细胞拥有这些细胞器，但还包含由纤维素构成的坚硬细胞壁、用于储存汁液的大液泡，以及进行光合作用的叶绿体。特化细胞，如红血细胞（无核、双凹形以携带更多氧气）和根毛细胞（长突起以吸收水分），其结构特化以高效执行特定功能。
3. Atoms, Elements and Compounds | 原子、元素与化合物
Everything is made of atoms. An element contains only one type of atom, classified in the Periodic Table. Each atom has a nucleus of protons (positive) and neutrons (neutral), surrounded by electrons (negative) arranged in shells. The atomic number is the number of protons, while the mass number is protons plus neutrons.
万物皆由原子构成。元素只含有一种原子，在周期表中分类排列。每个原子都有一个由质子（正电）和中子（中性）组成的原子核，周围电子（负电）按壳层排列。原子序数是质子数，质量数是质子数加中子数。
Compounds form when two or more elements chemically combine, such as water (H₂O) or carbon dioxide (CO₂). Chemical bonds include ionic bonding (transfer of electrons between metal and non-metal) and covalent bonding (sharing of electrons between non-metals). The formula of an ionic compound shows the simplest ratio of ions, e.g., NaCl, while molecular formulae show exact atom numbers.
当两种或多种元素通过化学方式结合时就形成化合物，如水(H₂O)或二氧化碳(CO₂)。化学键包括离子键（金属与非金属之间电子转移）和共价键（非金属之间电子共用）。离子化合物的化学式表示离子的最简比例，如NaCl；分子式则表示精确的原子数目。
4. States of Matter and the Particle Model | 物质状态与粒子模型
Matter exists in three main states: solid, liquid, and gas. The particle model explains the properties of each state. In solids, particles are tightly packed in fixed positions, vibrating slightly; they have a fixed shape and volume. In liquids, particles are close but can slide past each other, taking the shape of the container but maintaining a fixed volume.
物质存在三种主要状态：固态、液态和气态。粒子模型解释了每种状态的性质。固体中粒子紧密排列在固定位置上，轻微振动；它们有固定的形状和体积。液体中粒子靠近但可互相滑过，呈容器形状但保持固定体积。
In gases, particles are far apart, moving rapidly in random directions; gases have no fixed shape or volume and can be compressed. Changes of state — melting, freezing, boiling, condensing, sublimation — involve energy transfer without altering chemical composition. The temperature remains constant during a state change, as energy is used to overcome interparticle forces.
气体中粒子相距很远，快速随机运动；气体没有固定的形状或体积，可被压缩。状态变化——熔化、凝固、沸腾、冷凝、升华——涉及能量转移但不改变化学组成。状态变化期间温度保持不变，因为能量用于克服粒子间作用力。
5. Energy Forms and Transfers | 能量形式与能量传递
Energy is the capacity to do work. It exists in various forms: kinetic, thermal, chemical, gravitational potential, elastic potential, electrical, magnetic, nuclear, and light. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred, stored, or dissipated.
能量是做功的能力。它以多种形式存在：动能、热能、化学能、重力势能、弹性势能、电能、磁能、核能和光能。能量守恒定律指出，能量不能被创造或消灭，只能被转移、储存或耗散。
Heat transfer occurs via conduction (mainly in solids through particle vibration and electron movement), convection (in fluids, where heated regions expand and become less dense, rising), and radiation (infrared waves that travel through a vacuum). The efficiency of an energy transfer is calculated as useful output energy divided by total input energy, often expressed as a percentage.
热传递通过传导（主要在固体中通过粒子振动和电子运动）、对流（流体中，受热区域膨胀密度变小而上升）和辐射（在真空中传播的红外波）发生。能量传递效率的计算为有用输出能量除以总输入能量，常以百分比表示。
6. Forces and Motion | 力与运动
A force is a push or pull that can change an object's shape, speed, or direction. Forces are vector quantities, having both magnitude and direction. The resultant force is the single force that has the same effect as all the forces acting on an object. When resultant force is zero, the object remains at rest or moves at constant velocity (Newton's First Law).
力是能改变物体形状、速度或方向的推或拉。力是矢量，既有大小又有方向。合力是一个单独力，其效果与作用在物体上所有力相同。当合力为零时，物体保持静止或匀速直线运动（牛顿第一定律）。
Newton's Second Law relates force, mass, and acceleration:
F = m × a
(Force = mass × acceleration). The acceleration due to gravity near Earth's surface is approximately 10 m/s². Motion can be described using graphs, such as distance–time graphs (gradient = speed) and velocity–me graphs (gradient = acceleration, area under graph = distance). Equations of motion like v = u + at are essential for calculations.牛顿第二定律关联了力、质量和加速度：
F = m × a
（力 = 质量 × 加速度）。地球表面附近的重力加速度约为10 m/s²。运动可以用图表描述，如距离-时间图（斜率=速度）和速度-时间图（斜率=加速度，图下面积=距离）。运动方程如 v = u + at 对计算至关重要。7. Chemical Reactions and Equations | 化学反应与方程式
A chemical reaction involves the rearrangement of atoms to form new substances. Reactants are transformed into products. The total mass is conserved, so chemical equations must be balanced. Word equations give the names of reactants and products, while symbol equations use chemical symbols and state symbols (s, l, g, aq).
化学反应涉及原子重新排列形成新物质。反应物转变为生成物。总质量守恒，因此化学方程式必须配平。文字方程式给出反应物和生成物的名称，而符号方程式使用化学符号和状态符号（s, l, g, aq）。
r). The reactivity series helps predict displacement: potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead, (hydrogen), copper, silver, gold.
反应类型包括燃烧（与氧气快速反应释放热和光）、热分解（通过加热分解）、置换（更活泼元素将较不活泼元素替换出来）和中和（酸+碱→盐+水）。活动性顺序有助于预测置换反应：钾、钠、钙、镁、铝、碳、锌、铁、锡、铅、（氢）、铜、银、金。
8. Photosynthesis and Plant Transport | 光合作用与植物运输
Photosynthesis is the process by which plants convert light energy into chemical energy, stored as glucose. The word equation is:
carbon dioxide + water → glucose + oxygen
in the presence of light and chlorophyll. The balanced symbol equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. This reaction takes place in the chloroplasts.光合作用是植物将光能转化为化学能并以葡萄糖形式储存的过程。文字方程式为：
二氧化碳 + 水 → 葡萄糖 + 氧气
在光和叶绿素存在下。配平的符号方程式为 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。该反应发生在叶绿体中。Water and minerals are transported in plants via xylem vessels, while sucrose and amino acids are transported in phloem sieve tubes (translocation). Transpiration, the evaporation of water from leaves, creates a tension that pulls water up the plant. Factors affecting transpiration include light intensity, temperature, humidity, and wind speed.
水分和矿物质通过木质部导管在植物体内运输，而蔗糖和氨基酸则在韧皮部筛管中运输（转运）。蒸腾作用，即水分从叶片蒸发，产生拉力将水分沿植物体拉上来。影响蒸腾作用的因素包括光照强度、温度、湿度和风速。
9. Electricity and Circuits | 电与电路
Electric current is the flow of charge. In metallic conductors, it is the flow of free electrons. For a current to flow, a circuit must be complete and there must be a source of potential difference (voltage). Current (I) is measured in amperes (A), potential difference (V) in volts (V), and resistance (R) in ohms (Ω).
电流是电荷的流动。在金属导体中，它是自由电子的流动。要产生电流，电路必须完整且必须有电势差（电压）源。电流(I)以安培(A)为单位，电势差(V)以伏特(V)为单位，电阻(R)以欧姆(Ω)为单位。
Ohm's Law states that:
V = I × R
provided temperature remains constant. In series circuits, current is the same everywhere, but the total resistance is the sum of individual resistances. In parallel circuits, voltage is the same across each branch, while current is divided. Electrical power can be calculated using P = I × V or P = I² × R.欧姆定律指出：
V = I × R
前提是温度保持不变。在串联电路中，各处电流相同，但总电阻为各电阻之和。在并联电路中，各支路电压相同，而电流分流。电功率可用 P = I × V 或 P = I² × R 计算。10. Periodic Table and Chemical Families | 周期表与化学族
The Periodic Table arranges elements in order of increasing atomic number. Vertical columns are called groups; elements in the same group have similar chemical properties because they have the same number of outer-shell electrons. Group 1 (alkali metals) are soft, reactive metals that react vigorously with water. Group 7 (halogens) are reactive non-metals; reactivity decreases down the group.
周期表按原子序数递增的顺序排列元素。纵列称为族；同一族元素具有相似的化学性质，因为它们最外层电子数相同。第1族（碱金属）是质地柔软、反应性强的金属，与水剧烈反应。第7族（卤素）是反应性强的非金属；反应性沿族向下减弱。
Group 0 (noble gases) are inert and monatomic due to full outer shells. The transition metals, located in the centre of the table, form coloured compounds, often act as catalysts, and have variable oxidation states. Trends across a period include changes in metallic character: from metallic on the left to non-metallic on the right.
第0族（惰性气体）因外层电子已满而呈惰性、单原子状态。位于周期表中央的过渡金属，能形成有色化合物，常用作催化剂，并具有可变的氧化态。周期中的变化趋势包括金属性的变化：从左边的金属递变为右边的非金属。
11. Waves and the Electromagnetic Spectrum | 波与电磁波谱
Waves transfer energy without transferring matter. Transverse waves (e.g., light, water ripples) oscillate perpendicular to the direction of energy transfer. Longitudinal waves (e.g., sound) oscillate parallel to the direction of energy transfer, consisting of compressions and rarefactions. Key wave properties are amplitude, wavelength, frequency, and wave speed.
波传递能量而不传递物质。横波（例如光、水波）的振动方向与能量传递方向垂直。纵波（例如声波）的振动方向与能量传递方向平行，由压缩和稀疏构成。波的关键性质有振幅、波长、频率和波速。
The wave equation is:
v = f × λ
vel at the speed of light in a vacuum (3.0 × 10⁸ m/s) and have different uses and dangers.波的方程是：
v = f × λ
其中 v 为波速(m/s)，f 为频率(Hz)，λ 为波长(m)。电磁波谱从长波到短波依次为：无线电波、微波、红外线、可见光、紫外线、X射线和伽马射线。所有波在真空中均以光速(3.0 × 10⁸ m/s)传播，并各有不同用途和危害。12. Inheritance and Evolution | 遗传与进化
Heredity is the passing of genetic information from parents to offspring. DNA, a double-helix polymer, contains genes that code for proteins. A gene is a section of DNA, and alleles are different versions of a gene. The genotype describes the genetic makeup, while the phenotype is the observable characteristic resulting from the genotype and the environment.
遗传是亲代将遗传信息传递给后代的过程。DNA是双螺旋聚合物，含有编码蛋白质的基因。基因是DNA的一个片段，等位基因是基因的不同版本。基因型描述基因组成，而表现型是基因型和环境共同作用下可观察到的特征。
for tall, where T is dominant), the expected phenotype ratio is 3:1. Natural selection, proposed by Charles Darwin, explains evolution: organisms with advantageous traits are more likely to survive, reproduce, and pass on those alleles, leading to gradual changes in the population.
单基因杂交可用庞纳特方格表示。在杂合亲本杂交中（如高茎Tt × Tt，T为显性），预期表现型比例为3:1。查尔斯·达尔文提出的自然选择学说解释了进化：具有有利特征的生物更可能存活、繁殖并传递这些等位基因，导致种群逐渐发生变化。
Published by TutorHao | Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图