📚 Year 9 Edexcel Science: Core Knowledge Review | 九年级爱德思科学：核心知识点梳理
Year 9 Edexcel Science consolidates the key concepts across biology, chemistry and physics, preparing you for IGCSE and beyond. This article revisits the essential knowledge you need to master: from cells and atoms to forces and energy transfers. A solid grasp of these fundamentals will strengthen your scientific thinking and practical skills.
九年级爱德思科学课程整合了生物、化学与物理的核心概念，为 IGCSE 及后续学习奠定基础。本文梳理你必须掌握的关键知识：从细胞和原子到力与能量转移。牢固掌握这些基础内容将强化你的科学思维和实验技能。
1. Cells, Tissues and Organs | 细胞、组织与器官
All living things are made of cells. Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria, while plant cells also have a cell wall, chloroplasts and a permanent vacuole.
所有生物都由细胞构成。动物细胞含有细胞核、细胞质、细胞膜和线粒体，植物细胞则还有细胞壁、叶绿体和一个永久液泡。
Specialised cells are adapted to perform specific functions. For example, red blood cells have no nucleus to carry more haemoglobin, and root hair cells have a large surface area for absorbing water.
特化细胞经适应后可执行特定功能。例如，红细胞没有细胞核以便携带更多血红蛋白，根毛细胞具有很大的表面积以吸收水分。
Tissues are groups of similar cells working together. Organs are made of different tissues, and organ systems consist of several organs that cooperate, such as the digestive system.
组织是由相似细胞组成的群体。器官由不同的组织构成，器官系统则由多个协同工作的器官组成，如消化系统。
2. Respiration and Photosynthesis | 呼吸作用与光合作用
Aerobic respiration releases energy from glucose using oxygen. The word equation is:
有氧呼吸利用氧气从葡萄糖中释放能量。其文字方程式为：
glucose + oxygen → carbon dioxide + water (+ energy)
葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）
This process occurs in the mitochondria of cells and is essential for all life processes including movement, growth and repair.
该过程发生在细胞的线粒体中，对于运动、生长和修复等所有生命过程至关重要。
Photosynthesis is how plants make their own food using light energy. The overall word equation is:
光合作用是植物利用光能制造自身养分的方式。总文字方程式为：
carbon dioxide + water → glucose + oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
Photosynthesis takes place in chloroplasts and requires chlorophyll. Light intensity, carbon dioxide concentration and temperature all affect the rate.
光合作用在叶绿体中进行，需要叶绿素。光照强度、二氧化碳浓度和温度都会影响光合速率。
3. Ecological Relationships | 生态关系
Food chains show the transfer of energy from producers to consumers. Producers (e.g. green plants) capture sunlight, primary consumers eat producers, and secondary consumers eat primary consumers.
食物链显示能量从生产者向消费者的转移。生产者（如绿色植物）捕获阳光，初级消费者吃生产者，次级消费者吃初级消费者。
Food webs are made of interconnected food chains. Predators kill and eat prey, and the populations of each species depend on one another.
食物网由相互连接的食物链组成。捕食者杀死并吃掉猎物，各物种的种群数量相互依赖。
All organisms compete for resources such as food, water and space. Adaptations – structural, behavioural or physiological – help organisms survive in their habitats.
所有生物都为食物、水和空间等资源而竞争。适应——结构上的、行为上的或生理上的——帮助生物在其栖息地生存。
4. States of Matter and Particle Theory | 物质状态与粒子理论
The three states of matter are solid, liquid and gas. In solids, particles vibrate in fixed positions; in liquids, they move past each other; in gases, they move rapidly in all directions.
物质的三态为固态、液态和气态。固体中粒子在固定位置振动；液体中粒子相互滑动；气体中粒子向各个方向快速运动。
Changes of state include melting, freezing, boiling, evaporation, condensation and sublimation. These are physical changes because no new substances are formed.
物态变化包括熔化、凝固、沸腾、蒸发、凝结和升华。这些属于物理变化，因为没有新物质生成。
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It happens faster in hotter conditions because particles have more kinetic energy.
扩散是粒子从高浓度区域向低浓度区域的运动。在更热的条件下扩散更快，因为粒子具有更多动能。
The particle model explains properties such as density: solids are usually denser than liquids and gases because their particles are packed more closely together.
粒子模型可以解释密度等性质：固体通常比液体和气体密度大，因为其粒子排列得更紧密。
5. Atoms, Elements and Compounds | 原子、元素与化合物
All substances are made of atoms. An element contains only one type of atom and is listed on the Periodic Table. Examples include oxygen (O), iron (Fe) and carbon (C).
所有物质都由原子构成。元素仅含一种原子，并列入周期表中。例如氧（O）、铁（Fe）和碳（C）。
A compound is formed when two or more elements chemically combine in fixed proportions. For instance, water (H₂O) always contains two hydrogen atoms for every oxygen atom.
当两种或多种元素以固定比例化合时，形成化合物。例如，水（H₂O）总是每1个氧原子对应2个氢原子。
The Periodic Table arranges elements in order of increasing atomic number. Vertical groups contain elements with similar chemical properties.
周期表按原子序数递增的顺序排列元素。同一竖列（族）的元素具有相似的化学性质。
Atoms of Group 1 are very reactive metals, while Group 7 contains highly reactive non-metals. Group 0, the noble gases, are unreactive because they have a full outer shell.
第1族为极活泼的金属，第7族为高度活泼的非金属。第0族是稀有气体，因其最外层电子已满而性质不活泼。
6. 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 change into products. Signs of a reaction include colour change, gas production and temperature change.
化学反应涉及原子重新排列以形成新物质。反应物转变为生成物。反应迹象包括颜色变化、气体产生和温度改变。
Combustion reactions require oxygen and release heat and light. The complete combustion of a hydrocarbon fuel yields carbon dioxide and water:
燃烧反应需要氧气并释放热和光。碳氢燃料的完全燃烧产生二氧化碳和水：
fuel + oxygen → carbon dioxide + water
燃料 + 氧气 → 二氧化碳 + 水
In a thermal decomposition reaction, a single compound breaks down into simpler substances when heated. For example, calcium carbonate decomposes to calcium oxide and carbon dioxide.
在热分解反应中，单一化合物受热分解为更简单的物质。例如，碳酸钙分解生成氧化钙和二氧化碳。
Word equations represent reactions simply, while symbol equations show the chemical symbols and must be balanced so that the number of atoms is the same on both sides.
文字方程式简单表示反应，而符号方程式展示化学符号，必须配平使两侧原子数相等。
7. Forces and Motion | 力与运动
A force is a push or a pull, measured in newtons (N). Forces can change an object’s speed, direction or shape. Contact forces include friction and air resistance; non-contact forces include gravity and magnetism.
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。接触力包括摩擦力和空气阻力；非接触力包括重力和磁力。
Speed is the distance travelled per unit time. Average speed can be calculated using:
速度是单位时间内通过的路程。平均速度可通过下式计算：
speed = distance ÷ time
速度 = 路程 ÷ 时间
Distance–time graphs show motion. A straight, sloping line indicates constant speed; a horizontal line means the object is stationary. The steeper the line, the faster the speed.
距离–时间图展示运动状态。一条倾斜直线表示匀速；水平线意味着物体静止。直线越陡，速度越快。
Balanced forces result in no change in motion (constant velocity or stationary). Unbalanced forces cause acceleration or deceleration.
平衡力作用不会改变运动状态（匀速或静止）。非平衡力会导致加速或减速。
8. Energy Forms and Transfers | 能量形式与转移
Energy exists in many forms, such as kinetic, thermal, light, sound, chemical, elastic potential and gravitational potential. The unit of energy is the joule (J).
能量存在多种形式，如动能、热能、光能、声能、化学能、弹性势能和重力势能。能量的单位是焦耳（J）。
Energy can be transferred between stores. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted from one form to another.
能量可以在存储库之间转移。能量守恒定律指出，能量既不能创生也不能消灭，只能转移或从一种形式转换为另一种形式。
Sankey diagrams show how much energy is usefully transferred and how much is wasted. Wasted energy is often dissipated as heat to the surroundings.
桑基图显示多少能量被有效转移，多少被浪费。浪费的能量通常以热的形式散失到周围环境中。
Efficiency is calculated as: efficiency = (useful output energy ÷ total input energy) × 100%. High efficiency reduces energy waste.
效率计算公式为：效率 = （有用输出能量 ÷ 总输入能量）× 100%。高效率可以减少能量浪费。
9. Electricity and Circuits | 电与电路
An electric current is the flow of electric charge, usually carried by electrons in metals. Current (I) is measured in amperes (A) and flows from the positive to the negative terminal in conventional terms.
电流是电荷的流动，在金属中通常由电子携带。电流（I）以安培（A）为单位，根据常规方向从正极流向负极。
Voltage (potential difference) is the push that drives the current around a circuit, measured in volts (V). Resistance, measured in ohms (Ω), opposes the current.
电压（电势差）是驱动电流在电路中流动的推力，以伏特（V）为单位。电阻以欧姆（Ω）为单位，阻碍电流。
Series circuits have a single loop; the current is the same everywhere, but the voltage is shared across components. In parallel circuits, the current splits, but each component gets the full source voltage.
串联电路为单一回路；各处电流相同，但各元件分担电压。在并联电路中，电流分流，但每个元件获得全部电源电压。
Circuit diagrams use standard symbols for components like cells, switches, bulbs and resistors. Ammeters are connected in series to measure current; voltmeters are connected in parallel to measure voltage.
电路图使用标准符号表示元件，如电池、开关、灯泡和电阻。安培表串联接入以测量电流；伏特表并联接入以测量电压。
10. Waves: Sound and Light | 波：声与光
Waves transfer energy without transferring matter. Transverse waves (like light) have oscillations perpendicular to the energy direction; longitudinal waves (like sound) have oscillations parallel to it.
波传递能量而不传递物质。横波（如光）的振动方向与能量传播方向垂直；纵波（如声）的振动方向与能量传播方向平行。
The amplitude of a wave is the height from the rest position, which determines loudness in sound or brightness in light. Frequency is the number of complete waves per second, measured in hertz (Hz), and determines pitch.
波的振幅是从平衡位置起的最大位移，决定声音的响度或光的亮度。频率是每秒完整波的数目，以赫兹（Hz）为单位，决定声音音调。
Sound travels fastest in solids and slowest in gases. It cannot travel through a vacuum. The speed of sound in air is approximately 340 m/s.
声音在固体中传播最快，在气体中最慢。声音不能在真空中传播。空气中的声速约为340 m/s。
Light travels in straight lines and at about 300,000 km/s in a vacuum. Reflection obeys the law: angle of incidence equals angle of reflection. Refraction is the bending of light as it passes from one medium to another.
光沿直线传播，在真空中速度约为300000 km/s。反射遵循定律：入射角等于反射角。折射是光从一种介质进入另一种介质时发生的弯曲现象。
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