Year 7 CAIE Science: Core Knowledge Summary | Year 7 CAIE 科学：核心知识点梳理

📚 Year 7 CAIE Science: Core Knowledge Summary | Year 7 CAIE 科学：核心知识点梳理

Year 7 CAIE Science introduces students to the fundamentals of Biology, Chemistry, and Physics, while building essential skills in scientific enquiry. This article provides a structured summary of the core knowledge students are expected to master, from the building blocks of life to the principles of energy and forces. Use this guide to consolidate your learning, identify key concepts, and prepare effectively for assessments.

Year 7 CAIE 科学带领学生进入生物、化学和物理的基础世界，同时培养重要的科学探究能力。本文系统地梳理了学生需要掌握的核心知识点，从构成生命的基本单元到能量与力的原理。你可以通过这份梳理巩固所学内容、锁定关键概念，并有针对性地准备考试。

1. Scientific Enquiry Skills | 科学探究技能

All scientific work begins with careful observation and questioning. In Year 7, you learn to formulate a testable hypothesis, identify variables (independent, dependent, and control), and design fair experiments. Recording data accurately in tables and representing it with graphs are fundamental skills. You also develop the ability to evaluate results, spot anomalous data, and draw evidence‑based conclusions.

所有科学研究都始于细致的观察和提问。在 Year 7，你需要学习提出可验证的假设，识别变量（自变量、因变量和控制变量），并设计公平的实验。准确地在表格中记录数据并用图表呈现是基本技能。你还需要培养评估结果、识别异常数据并得出基于证据的结论的能力。

Variables: Independent variable is the one you change; dependent variable is what you measure; control variables keep the test fair. / 变量：自变量是你改变的量；因变量是你测量的量；控制变量保持测试公平。
Graphs: Line graphs show continuous data, bar charts show discrete categories. / 图表：线形图展示连续数据，条形图展示离散类别。
Safety: Always wear goggles, tie back long hair, and follow your teacher’s instructions. / 安全：务必佩戴护目镜，束好长发，并听从老师的指导。

2. Cells and Organisation | 细胞与组织结构

Living things are made of cells. Animal and plant cells share common structures such as a nucleus, cytoplasm, cell membrane, and mitochondria. Plant cells also have a rigid cell wall, a large permanent vacuole, and chloroplasts for photosynthesis. Cells group together to form tissues, tissues work together in organs, and organs form organ systems such as the digestive system.

生物体由细胞构成。动物细胞和植物细胞有共同的结构，如细胞核、细胞质、细胞膜和线粒体。植物细胞还有坚硬的细胞壁、一个大的中央液泡以及进行光合作用的叶绿体。细胞聚集形成组织，组织协同工作构成器官，器官则组成器官系统，比如消化系统。

Part	Function	部件	功能
Nucleus	Controls the cell and contains DNA	细胞核	控制细胞活动，含有遗传物质
Cytoplasm	Jelly‑like substance where chemical reactions occur	细胞质	胶状物质，进行化学反应
Mitochondria	Release energy through respiration	线粒体	通过呼吸作用释放能量
Chloroplasts	Absorb light for photosynthesis (plant only)	叶绿体	吸收光能进行光合作用（仅植物）

Specialised cells are adapted to perform specific functions. For example, red blood cells have no nucleus to carry more oxygen; root hair cells have a large surface area to absorb water. Understanding these adaptations helps explain how organisms survive.

特化细胞经过适应以执行特定功能。例如，红细胞没有细胞核以便携带更多氧气；根毛细胞具有很大的表面积来吸收水分。理解这些适应有助于解释生物体如何生存。

3. States of Matter | 物质的状态

Matter exists as solid, liquid, or gas. The particle model explains the properties of each state: solids have particles tightly packed in a fixed arrangement, liquids have particles close together but able to move past each other, and gases have particles far apart moving rapidly in all directions. Changes of state—melting, freezing, boiling, evaporation, condensation, and sublimation—occur when energy is added or removed.

物质以固态、液态或气态存在。粒子模型解释了每种状态的性质：固体的粒子紧密排列在固定位置上；液体的粒子紧挨着，但能够相互滑动；气体的粒子相距很远，朝各个方向快速运动。当加入或移除能量时，状态会发生变化——熔化、凝固、沸腾、蒸发、凝结和升华。

The temperature stays constant during a change of state even though heating continues; the energy is used to break inter‑particle forces rather than raise the temperature. Diffusion is faster in gases than in liquids because particles move more freely. This key idea is tested frequently.

在状态变化期间，即使持续加热温度也保持不变；此时能量用于打破粒子间的作用力，而不是提升温度。气体中的扩散比液体中更快，因为粒子运动更自由。这个核心概念经常被考查。

Melting point: temperature at which solid becomes liquid. / 熔点：固体变为液体的温度。
Boiling point: temperature at which liquid becomes gas throughout. / 沸点：液体整体变为气体的温度。

4. Atoms, Elements and Compounds | 原子、元素与化合物

All substances are made of tiny particles called atoms. An element is made from only one type of atom, and each element is represented by a chemical symbol, such as O for oxygen and Fe for iron. The Periodic Table arranges elements in order of increasing atomic number. A compound is formed when two or more different elements are chemically bonded, for example water (H₂O) and carbon dioxide (CO₂).

所有物质都由叫做原子的微小粒子组成。元素仅由一种原子构成，每种元素都用化学符号表示，如氧的符号是 O，铁的符号是 Fe。元素周期表按原子序数递增排列元素。当两种或两种以上不同元素通过化学键结合时，就形成化合物，例如水（H₂O）和二氧化碳（CO₂）。

Chemical reactions involve the rearrangement of atoms; no atoms are created or destroyed. This is the law of conservation of mass. Common signs of a chemical reaction include a colour change, temperature change, formation of a gas (bubbles), or a precipitate forming. Word equations summarise reactants → products.

化学反应涉及原子的重新排列；原子不会被创造或消灭，这就是质量守恒定律。化学反应的常见标志包括颜色变化、温度变化、产生气体（气泡）或生成沉淀。文字方程式归纳了：反应物 → 生成物。

Term	Definition	术语	定义
Element	Substance made from one type of atom	元素	由一种原子组成的物质
Compound	Two or more elements chemically combined in fixed proportions	化合物	两种或多种元素按固定比例化合而成
Mixture	Different substances not chemically joined, easily separated	混合物	不同物质没有化学结合，容易分离

5. Forces and Motion | 力与运动

A force is a push or a pull that can change an object’s speed, direction, or shape. Forces are measured in newtons (N). We represent forces with arrows in free‑body diagrams; the length of the arrow shows the size of the force. When forces are balanced, an object stays stationary or moves at a constant speed. Unbalanced forces cause acceleration or deceleration.

力是一种推或拉，可以改变物体的速度、方向或形状。力以牛顿（N）为单位。我们用力学示意图中的箭头表示力；箭头的长度表示力的大小。当力平衡时，物体保持静止或匀速运动。不平衡的力则引起加速或减速。

Key forces you must know include weight (the pull of gravity on a mass), friction (resistance between surfaces), air resistance, upthrust, and tension. Weight is calculated using the equation:

你必须掌握的关键力包括：重力（地球对质量的吸引）、摩擦力（表面间的阻力）、空气阻力、浮力和张力。重力的计算使用以下公式：

Weight (N) = mass (kg) × gravitational field strength (N/kg)

On Earth, gravitational field strength is approximately 10 N/kg. Speed is another fundamental concept:

在地球上，重力场强度约为 10 N/kg。速度是另一个基本概念：

Average speed = distance ÷ time

Hooke’s Law applies to elastic objects: the extension of a spring is directly proportional to the applied force, until the elastic limit is reached. Understanding force and motion is essential for explaining everything from falling objects to braking cars.

胡克定律适用于弹性物体：弹簧的伸长量与施加的力成正比，直到达到弹性极限。理解力与运动对于解释从落体到汽车制动的各种现象至关重要。

6. Energy | 能量

Energy is the ability to do work. It is measured in joules (J). Energy can be transferred, stored, or dissipated, but it is never created or destroyed (conservation of energy). In Year 7 you learn about different energy stores: kinetic, gravitational potential, elastic potential, thermal (internal), chemical, and electrostatic. Energy is transferred between stores through pathways such as heating, mechanical work, electrical work, and radiation.

能量是做功的能力，单位为焦耳（J）。能量可以转移、储存或耗散，但绝不能被创造或消灭（能量守恒定律）。在 Year 7，你会学习不同的能量储存方式：动能、重力势能、弹性势能、热能（内能）、化学能和静电能量。能量通过加热、机械做功、电力做功和辐射等途径在储存库之间转移。

Fossil fuels (coal, oil, natural gas) are non‑renewable because they take millions of years to form. Renewable energy resources—solar, wind, wave, hydroelectric, geothermal—can be replenished. They are important for a sustainable future but may have disadvantages such as high initial cost or unreliability.

化石燃料（煤、石油、天然气）是不可再生的，因为它们需要数百万年才能形成。可再生能源——太阳能、风能、波浪能、水力发电、地热能——可以补充。它们对可持续的未来至关重要，但也可能有初始成本高或不够可靠等缺点。

Conduction, convection, and radiation are the three methods of thermal energy transfer. Conduction occurs mainly in solids, convection in fluids (liquids and gases), and radiation can travel through a vacuum. Good insulators like air reduce unwanted energy transfers.

传导、对流和辐射是热能传递的三种方式。传导主要发生在固体中，对流发生在流体（液体和气体）中，而辐射可以在真空中传播。像空气这样的优良绝热体可以减少不必要的能量转移。

7. Electricity | 电学

An electric circuit needs a complete loop for current to flow. Current is the flow of electric charge, measured in amperes (A). Voltage (potential difference) is the push that drives the charge around, measured in volts (V). Components such as bulbs, motors, and buzzers convert electrical energy into other forms.

电路需要一个完整的回路才能有电流流过。电流是电荷的流动，单位为安培（A）。电压（电势差）是推动电荷运动的“推力”，单位为伏特（V）。灯泡、马达和蜂鸣器等元器件将电能转化为其他形式的能量。

There are two basic circuit types: series and parallel. In a series circuit, all components are connected end‑to‑end; if one bulb breaks, the circuit is open and all bulbs go out. Current is the same everywhere. In a parallel circuit, each component has its own branch; a break in one branch does not affect the others. Current is shared between branches, but voltage across each branch is the same.

基本电路有两种类型：串联和并联。在串联电路中，所有元器件首尾相连；如果一个灯泡损坏，电路断开，所有灯泡都熄灭。串联电路中各处电流相同。在并联电路中，每个元器件有自己的支路；一条支路断开不会影响其他支路。各支路分享总电流，但每条支路的电压相同。

Conductors (metals like copper) allow charge to flow easily; insulators (plastic, rubber) do not. Resistance is a measure of how difficult it is for current to flow; it is measured in ohms (Ω). Adding more bulbs in series increases total resistance, reducing current. Always draw circuit diagrams with standard symbols: straight lines for wires, a circle with a cross for a bulb, etc.

导体（如铜等金属）允许电荷轻松通过；绝缘体（塑料、橡胶）则不能。电阻是衡量电流流通难易程度的量，单位是欧姆（Ω）。在串联电路中增加更多灯泡会增大总电阻，从而减小电流。绘制电路图时务必使用标准符号：直线表示导线，带叉的圆圈表示灯泡等。

8. Waves: Sound and Light | 波：声音与光

Sound travels as longitudinal waves caused by vibrating particles. It needs a medium (solid, liquid, or gas) to travel; it cannot move through a vacuum. The speed of sound is about 340 m/s in air. Sound waves reflect to produce echoes. Changing the amplitude of a sound wave changes its loudness; changing the frequency changes its pitch.

声音以纵波形式传播，由粒子的振动引起。声音传播需要介质（固体、液体或气体）；不能在真空中传播。声音在空气中的速度约为 340 m/s。声波反射会产生回声。改变声波的振幅会改变响度；改变频率则会改变音调。

Light travels as transverse waves at a much higher speed—about 300,000 km/s in a vacuum. Light can travel through a vacuum, which is why we receive sunlight. When light hits a surface, it can be absorbed, reflected, or transmitted. The law of reflection states that the angle of incidence equals the angle of reflection. Refraction occurs when light passes from one transparent medium to another and changes speed, bending the ray.

光以横波形式传播，速度极快——真空中约为 300,000 km/s。光可以在真空中传播，这就是我们能接收到太阳光的原因。当光照射到表面时，会被吸收、反射或透射。反射定律指出，入射角等于反射角。当光从一种透明介质进入另一种介质时，速度发生变化，光线弯曲，这就是折射。

White light can be dispersed by a prism into the colours of the visible spectrum: red, orange, yellow, green, blue, indigo, violet. Coloured filters transmit only certain colours of light. Understanding wave behaviour helps explain how we see objects and hear sounds.

白光束穿过棱镜可以色散出可见光谱的颜色：红、橙、黄、绿、蓝、靛、紫。彩色滤光片只透过特定颜色的光。理解波的行为有助于解释我们是如何看到物体和听到声音的。

9. Earth and the Atmosphere | 地球与大气层

Earth’s structure consists of the inner core, outer core, mantle, and crust. The crust is broken into tectonic plates that move slowly, causing earthquakes and volcanic activity. The rock cycle describes how igneous, sedimentary, and metamorphic rocks are formed and changed over geological time. Weathering and erosion break rocks down into sediments that are transported and deposited.

地球的内部结构包括内核、外核、地幔和地壳。地壳破碎成许多构造板块，缓慢移动，引发地震和火山活动。岩石循环描述了火成岩、沉积岩和变质岩如何在地质时间尺度上形成和转化。风化和侵蚀将岩石分解成沉积物，这些沉积物被搬运并沉积。

The atmosphere is a mixture of gases: about 78% nitrogen, 21% oxygen, and 0.04% carbon dioxide, with variable water vapour. The ozone layer in the stratosphere absorbs harmful ultraviolet radiation from the Sun. Human activities, such as burning fossil fuels, increase carbon dioxide levels, contributing to the greenhouse effect and global warming. The carbon cycle shows how carbon moves between the atmosphere, living organisms, and the oceans.

大气层是一种混合气体：约 78% 的氮气、21% 的氧气以及 0.04% 的二氧化碳，还有含量变化的水蒸气。平流层中的臭氧层吸收太阳有害的紫外线辐射。燃烧化石燃料等人类活动增加了二氧化碳的浓度，加剧了温室效应和全球变暖。碳循环展示了碳如何在大气、生物体和海洋之间流动。

Igneous rock: forms from cooled magma or lava (e.g. granite, basalt). / 火成岩：由岩浆或熔岩冷却形成（如花岗岩、玄武岩）。
Sedimentary rock: forms from compressed layers of sediment (e.g. sandstone, limestone). / 沉积岩：由沉积物层层压实形成（如砂岩、石灰岩）。
Metamorphic rock: forms when existing rocks are changed by heat and pressure (e.g. marble, slate). / 变质岩：原有岩石在高温高压下变质形成（如大理岩、板岩）。

10. Nutrition, Digestion and Reproduction | 营养、消化与生殖

A balanced diet provides the nutrients needed for energy, growth, and repair. The major food groups are carbohydrates (energy), proteins (growth and repair), lipids (insulation and energy store), vitamins and minerals (body processes), fibre (keeps the digestive system healthy), and water. Food tests help identify these nutrients: iodine turns blue‑black with starch; Benedict’s solution turns orange‑red with simple sugars when heated; Biuret reagent turns purple with protein.

均衡的膳食提供能量、生长和修复所需的营养素。主要的食物类别有：碳水化合物（提供能量）、蛋白质（生长与修复）、脂类（隔热和能量储存）、维生素和矿物质（身体机能）、纤维（保持消化系统健康）以及水。食物检测有助于识别这些营养素：碘液遇淀粉变蓝黑色；本尼迪克特溶液加热后遇单糖呈橙红色；双缩脲试剂遇蛋白质变紫色。

The digestive system breaks large insoluble food molecules into small soluble ones that can be absorbed into the blood. Enzymes in the mouth, stomach, and small intestine speed up this breakdown. Villi in the small intestine provide a large surface area for absorption. Peristalsis moves food along the gut by muscle contractions.

消化系统将大而不溶的食物分子分解为可溶解并吸收进入血液的小分子。口腔、胃和小肠中的酶加速了这一分解过程。小肠壁上的绒毛提供了巨大的吸收表面积。蠕动通过肌肉收缩推动食物沿消化道移动。

Living things reproduce to ensure survival of the species. In Year 7 you study the human reproductive systems, fertilisation, and the development of a foetus. The placenta allows exchange of nutrients and waste between mother and baby, but no mixing of blood. Puberty is the stage when the body becomes capable of reproduction, involving physical and emotional changes triggered by hormones.

生物通过繁殖确保物种的延续。在 Year 7 你将学习人类生殖系统、受精以及胎儿的发育。胎盘允许母体与胎儿之间营养物质和废物的交换，但血液不会混合。青春期是身体具备生殖能力的阶段，伴随着由激素引发的身体和情感变化。

Plants also reproduce, both sexually (flowering plants with pollination and fertilisation) and asexually (runners, bulbs, cuttings). Pollination is the transfer of pollen from an anther to a stigma; fertilisation leads to seed formation. Seeds are dispersed by wind, water, animals, or explosion to reduce competition.

植物也进行繁殖，包括有性繁殖（开花植物的传粉和受精）和无性繁殖（匍匐茎、鳞茎、扦插）。传粉是花粉从花药传到柱头的过程；受精导致种子形成。种子通过风、水、动物或爆炸力传播，以减少竞争。

11. Interdependence and Ecology | 相互依赖与生态

Ecology studies how living organisms interact with each other and their environment. A habitat is the place where an organism lives. A population is a group of the same species living in a habitat. All the populations together form a community. An ecosystem includes the community and the non‑living (abiotic) factors such as temperature, light, and water.

生态学研究生物体如何彼此相互作用并与环境互动。栖息地是生物生存的地方。种群是生活在同一栖息地的同种生物群体。所有种群共同构成一个群落。生态系统包括了群落以及温度、光照、水等非生物（无生命）因子。

Food chains and food webs show feeding relationships. Every chain starts with a producer (usually a green plant that photosynthesises). Primary consumers eat producers, secondary consumers eat primary consumers, and so on. Decomposers (bacteria and fungi) break down dead matter, returning nutrients to the soil. Energy is transferred along the chain, but much is lost at each stage as heat or movement.

食物链和食物网展示了摄食关系。每条链都以生产者（通常是进行光合作用的绿色植物）开始。初级消费者吃生产者，次级消费者吃初级消费者，依此类推。分解者（细菌和真菌）分解死亡物质，将养分归还土壤。能量沿食物链传递，但在每一级都有大量以热量或运动形式散失。

Photosynthesis is the process by which plants make their own food using sunlight. The word equation is:

光合作用是植物利用阳光制造自身养料的过程。其文字方程式为：

Carbon dioxide + water → glucose + oxygen

（carbon dioxide + water → glucose + oxygen）

Chlorophyll in chloroplasts captures light energy. This reaction takes place only in the light. Plants then store glucose as starch or use it for energy in respiration. Human activities like deforestation and pollution can disrupt ecosystems; conservation helps protect biodiversity.

叶绿体中的叶绿素捕获光能。这个反应只在光下进行。植物随后将葡萄糖以淀粉形式储存，或用于呼吸作用释放能量。毁林和污染等人类活动会破坏生态系统；保护自然有助于保护生物多样性。

12. Gravity, Space and the Solar System | 引力、太空与太阳系

Gravity is the force of attraction between all masses. The Sun’s huge gravitational pull keeps the Earth and other planets in orbit. Our Solar System consists of the Sun (a star), eight planets, their moons, dwarf planets, asteroids, and comets. The planets in order from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. You should know that Earth’s rotation on its axis takes 24 hours, causing day and night, while its orbit around the Sun takes 365.25 days, causing the seasons.

引力是存在于任何两个有质量的物体之间的吸引力。太阳的巨大引力使地球和其他行星保持在轨道上运行。我们的太阳系由太阳（一颗恒星）、八大行星、它们的卫星、矮行星、小行星和彗星组成。行星按照离太阳由近及远的顺序是：水星、金星、地球、火星、木星、土星、天王星、海王星。你需要知道，地球绕地轴自转一圈需要 24 小时，产生了昼夜交替；绕太阳公转一圈需要 365.25 天，产生了季节变化。

The Moon is Earth’s natural satellite. Its phases change in a regular cycle of about 29.5 days because we see different amounts of its sunlit half. Eclipses occur when Earth, Moon, and Sun align: a solar eclipse happens when the Moon casts a shadow on Earth; a lunar eclipse occurs when Earth blocks sunlight from reaching the Moon. Artificial satellites serve purposes such as communication, weather monitoring, and navigation.

月球是地球的天然卫星。它的月相以大约 29.5 天的周期有规律地变化，因为我们看到月球被照亮半球的不同部分。当地球、月球和太阳排成一线时会发生食：月食是地球挡住照向月球的阳光；日食是月球在地球上投下阴影。人造卫星用于通信、气象监测和导航等目的。

Scientists use telescopes and space probes to explore the Universe. The Earth is part of a Galaxy called the Milky Way. A light‑year is the distance light travels in one year, used to measure vast astronomical distances. Understanding our place in space helps us appreciate the scale of the cosmos and the conditions that have made life on Earth possible.

科学家利用望远镜和太空探测器探索宇宙。地球所在的星系叫做银河系。光年是光在一年中行进的距离，用于量度极大的天文距离。了解我们在太空中的位置有助于我们体会宇宙的尺度，以及造就地球生命的条件。

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Year 7 CAIE Science: Core Knowledge Summary | Year 7 CAIE 科学：核心知识点梳理