📚 Year 7 CIE Science: Core Knowledge Review | Year 7 CIE 科学：核心知识点梳理
Welcome to your Year 7 CIE Science revision guide. This article brings together the most important ideas from biology, chemistry and physics that you will study this year. Read through the notes carefully and test your understanding as you go.
欢迎阅读 Year 7 CIE 科学复习指南。本文整理了你将在这一年学习的生物学、化学和物理学中最重要的概念。请仔细阅读这些笔记，并随时检验自己的理解。
1. Living Things and Their Characteristics | 生物及其特征
All living things carry out seven life processes. These are captured by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.
所有生物都进行着七大生命过程，其首字母缩写为 MRS GREN：运动、呼吸、感应、生长、繁殖、排泄和营养。
Movement can be internal (e.g. moving substances inside an organism) or external (e.g. walking). Respiration is the chemical process of releasing energy from food. Sensitivity means detecting changes in the environment and responding to them. Growth is a permanent increase in size, while reproduction is the production of offspring. Excretion is the removal of toxic waste products from metabolism, and nutrition is taking in materials for energy, growth and repair.
运动可以是内部的（如体内运输物质）或外部的（如行走）。呼吸是从食物中释放能量的化学过程。感应意味着探测环境变化并作出反应。生长是体积的永久增大，繁殖是产生后代。排泄是代谢产生的有毒废物的排出，营养则是获取用于能量、生长和修复的物质。
Living things are also organised into groups based on shared features. The five kingdoms are Animals, Plants, Fungi, Prokaryotes (bacteria) and Protoctists (e.g. algae, amoeba). Vertebrates are further divided into mammals, birds, reptiles, amphibians and fish.
生物也根据共同特征被分为不同的类群。五大界是动物界、植物界、真菌界、原核生物界（细菌）和原生生物界（如藻类、变形虫）。脊椎动物又进一步分为哺乳动物、鸟类、爬行类、两栖类和鱼类。
2. Cells: Structure and Function | 细胞的结构与功能
Cells are the basic building blocks of life. All living organisms are made up of one or more cells. Animal and plant cells share several structures: the cell membrane, cytoplasm, nucleus and mitochondria.
细胞是生命的基本结构单位。所有生物体都由一个或多个细胞组成。动物细胞和植物细胞共享若干结构：细胞膜、细胞质、细胞核和线粒体。
The nucleus contains genetic material (DNA) and controls the cell's activities. The cell membrane is a selectively permeable barrier that controls what enters and leaves the cell. Cytoplasm is a jelly-like substance where most chemical reactions take place. Mitochondria are the sites of respiration, releasing energy.
细胞核含有遗传物质（DNA）并控制细胞的活动。细胞膜是具有选择透过性的屏障，控制物质进出。细胞质是凝胶状物质，大多数化学反应在此发生。线粒体是呼吸的场所，释放能量。
l sap, and chloroplasts that contain chlorophyll for photosynthesis. The chemical word equation for photosynthesis is: carbon dioxide + water → glucose + oxygen, using light energy.
植物细胞还有三个动物细胞不具备的结构：由纤维素构成的坚硬细胞壁，充满细胞液的大中央液泡，以及含有叶绿素、进行光合作用的叶绿体。光合作用的文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气，需要光能。
3. Reproduction in Plants and Animals | 植物与动物的繁殖
Reproduction can be sexual or asexual. Sexual reproduction involves two parents and the joining of male and female gametes (sperm and egg) to produce offspring that are genetically different from the parents. Asexual reproduction requires only one parent and produces genetically identical offspring (clones).
繁殖可分为有性生殖和无性生殖。有性生殖涉及两个亲本，雄配子（精子）与雌配子（卵细胞）结合，产生的后代与亲本在遗传上不同。无性生殖只需一个亲本，产生遗传上完全相同的后代（克隆）。
In humans, puberty brings about physical changes that enable reproduction. Male sex cells (sperm) are produced in the testes, while female sex cells (eggs) are released from the ovaries. Fertilisation occurs when the sperm nucleus fuses with the egg nucleus, forming a zygote. The zygote implants in the uterus and develops into an embryo.
在人类中，青春期带来的身体变化使生殖成为可能。雄配子（精子）在睾丸中产生，雌配子（卵细胞）从卵巢中排出。当精子的细胞核与卵细胞的细胞核融合时，发生受精，形成合子。合子植入子宫并发育成胚胎。
Flowering plants reproduce sexually through pollination and fertilisation. Pollen grains (male gametes) land on the stigma of a flower, grow a pollen tube down the style, and reach the ovary where fertilisation of the ovule takes place. The fertilised ovule becomes a seed, and the ovary develops into a fruit.
开花植物通过传粉和受精进行有性繁殖。花粉粒（雄配子）落在花的柱头上，长出花粉管并沿花柱向下生长，到达子房，胚珠在此受精。受精后的胚珠发育成种子，子房发育成果实。
4. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem is a community of living organisms interacting with each other and with their non-living environment. Habitats provide the necessary resources for organisms to survive, including food, water, shelter and suitable temperature.
生态系统是生物群落与其非生物环境相互作用的整体。栖息地为生物提供生存所必需的资源，包括食物、水、庇护所和适宜的温度。
Energy flows through an ecosystem along food chains and food webs. A food chain always starts with a producer, typically a green plant that makes its own food through photosynthesis. Primary consumers (herbivores) eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers. Decomposers, such as bacteria and fungi, break down dead organic matter and recycle nutrients back into the soil.
能量通过食物链和食物网在生态系统中流动。食物链总是以生产者开始，通常是能通过光合作用制造食物的绿色植物。初级消费者（食草动物）吃掉生产者，次级消费者吃掉初级消费者，三级消费者吃掉次级消费者。分解者，如细菌和真菌，分解死去的有机物，将养分循环回土壤。
Changes in the environment, such as a decrease in rainfall or the introduction of a new predator, can affect population sizes. For example, if a disease reduces the number of rabbits (primary consumers), the number of foxes (secondary consumers) may also decline due to less food being available.
环境变化，例如降雨量减少或引入新的捕食者，会影响种群数量。例如，如果一种疾病导致兔子（初级消费者）数量减少，狐狸（次级消费者）的数量也可能因食物不足而下降。
5. States of Matter and the Particle Model | 物质的态与粒子模型
All matter is made up of tiny particles. The three common states of matter are solid, liquid and gas. The particle model helps explain the properties of solids, liquids and gases in terms of the arrangement, movement and energy of particles.
所有物质都由微小的粒子组成。物质常见的三种状态是固态、液态和气态。粒子模型有助于从粒子的排列、运动及能量的角度解释固体、液体和气体的性质。
In a solid, particles are packed closely together in a regular pattern. They vibrate about fixed positions and cannot move freely. This gives solids a fixed shape and a fixed volume. In a liquid, particles are still close together but are arranged irregularly. They can slide past each other, allowing liquids to flow and take the shape of their container, but they keep a fixed volume. In a gas, particles are far apart and move randomly at high speeds. Gases have no fixed shape or volume and can be compressed easily.
在固体中，粒子紧密排列，形成规则的图案。它们在固定位置上振动，不能自由移动。这使得固体具有固定的形状和体积。在液体中，粒子仍然紧密但排列不规则。它们可以相互滑动，使液体能够流动并呈现容器的形状，但体积保持不变。在气体中，粒子相距很远，以高速随机运动。气体没有固定的形状或体积，容易压缩。
Changes of state are physical changes: melting (solid to liquid), freezing (liquid to solid), boiling/evaporation (liquid to gas) and condensation (gas to liquid). The reverse of boiling is condensation. During a change of state, the temperature stays constant even though heating continues, because the energy is used to break or form forces between particles.
状态变化属于物理变化：熔化（固态到液态）、凝固（液态到固态）、沸腾/蒸发（液态到气态）和凝结（气态到液态）。沸腾的逆过程是凝结。在状态变化过程中，尽管持续加热，温度却保持不变，因为能量用于打破或形成粒子之间的作用力。
6. Atoms, Elements and Compounds | 原子、元素与化合物
All substances are made from atoms. An element is a pure substance made of only one type of atom. Elements are listed on the Periodic Table, each with its own chemical symbol, such as H for hydrogen, O for oxygen and Fe for iron.
所有物质都由原子构成。元素是由仅一种原子组成的纯净物。元素列于元素周期表中，每种元素都有自己的化学符号，如 H 代表氢，O 代表氧，Fe 代表铁。
A compound is a pure substance made of two or more different elements chemically bonded together. The properties of a compound are different from the properties of the elements that make it up. For example, sodium chloride (NaCl) is a white crystalline solid used as table salt, but sodium is a highly reactive metal and chlorine is a poisonous green gas.
化合物是由两种或两种以上不同元素通过化学键结合而成的纯净物。化合物的性质与其组成元素的性质不同。例如，氯化钠（NaCl）是一种白色晶状固体，用作食盐，但钠是一种高度活泼的金属，氯是一种有毒的黄绿色气体。
Chemical formulas show the type and ratio of atoms in a compound. For instance, H₂O means two hydrogen atoms bonded to one oxygen atom. A mixture consists of two or more substances (elements or compounds) that are not chemically combined and can be separated by physical methods such as filtration, evaporation or distillation.
化学式表示化合物中原子的种类和比例。例如，H₂O 表示两个氢原子与一个氧原子结合。混合物由两种或多种物质（元素或化合物）组成，它们没有通过化学方式结合，可以通过过滤、蒸发或蒸馏等物理方法分离。
7. Forces and Motion | 力与运动
A force is a push or a pull that can change the speed, direction or shape of an object. Forces are measured in newtons (N). Key types of forces include weight (gravity pulling downwards), friction (opposes motion between surfaces), air resistance, tension and upthrust.
力是能改变物体速度、方向或形状的推或拉。力的单位是牛顿（N）。常见的力类型包括重力（地球向下的引力）、摩擦力（阻碍表面之间的运动）、空气阻力、张力和浮力。
When forces on an object are balanced (equal in size and opposite in direction), the object's motion does not change – it either remains still or continues moving at a steady speed in a straight line. Unbalanced forces cause a change in speed (acceleration or deceleration) or direction.
当物体受到的力平衡（大小相等、方向相反）时，物体的运动状态不变——它要么保持静止，要么继续沿直线匀速运动。非平衡力会导致速度变化（加速或减速）或方向改变。
ndard unit for speed is metres per second (m/s). Distance-time graphs show how far an object has travelled over a period of time. A straight, sloping line indicates constant speed; a horizontal line indicates the object is stationary.
速度可用公式计算：速度 = 路程 ÷ 时间。速度的标准单位是米每秒（m/s）。路程-时间图显示物体在一段时间内移动的距离。一条倾斜的直线表示匀速运动；水平线表示物体静止。
8. Energy Types and Transfers | 能量类型与转化
Energy is the ability to do work. The main stores (or forms) of energy include kinetic (movement), thermal (heat), chemical, gravitational potential, elastic potential, light, sound and electrical. Energy is measured in joules (J).
能量是做功的能力。能量的主要储存形式（或类型）包括动能（运动）、热能、化学能、重力势能、弹性势能、光能、声能和电能。能量的单位是焦耳（J）。
Energy can be transferred from one store to another, but it cannot be created or destroyed. This is the principle of conservation of energy. In a simple pendulum, energy constantly shifts between gravitational potential energy (at the highest points) and kinetic energy (at the lowest point).
能量可以从一种储存形式转化为另一种，但既不能被创造也不能被消灭。这就是能量守恒原理。在单摆中，能量不断在重力势能（在最高点）和动能（在最低点）之间转换。
ly transferred to the thermal store of the surroundings, making energy transfers never 100% efficient. Efficiency = (useful energy output ÷ total energy input) × 100% e used to visualise energy transfers, with arrow widths representing the amount of energy.
浪费的能量通常转移到周围环境的热能储存中，因此能量转换效率永远达不到100%。效率 =（有用能量输出 ÷ 总能量输入）× 100%。桑基图可用来直观展示能量传递，箭头的宽度表示能量的大小。
9. Electricity Basics | 电学基础
An electric current is the flow of electric charge, usually electrons, around a complete circuit. For a current to flow, a circuit must be closed and contain a source of potential difference, such as a cell or battery.
电流是电荷（通常是电子）在闭合回路中的流动。要使电流流动，电路必须是闭合的，并且要有电势差源，如电池。
Conductors, such as metals, allow charge to pass through easily because they contain free electrons. Insulators, such as plastic and rubber, do not allow charge to flow readily. Common circuit components include cells, bulbs, switches, buzzers, motors and resistors. They are represented by standard circuit symbols in diagrams.
导体（如金属）容易让电荷通过，因为它们含有自由电子。绝缘体（如塑料和橡胶）则不允许电荷轻易流动。常见的电路元件包括电池、灯泡、开关、蜂鸣器、电动机和电阻。它们在电路图中用标准的电路符号表示。
In a series circuit, there is only one complete path for the current. If one component breaks, the whole circuit stops working. The current is the same everywhere in a series circuit. In a parallel circuit, components are connected in separate branches, each providing an independent path for current. If one branch breaks, current can still flow through the other branches. Adding more bulbs in series makes them dimmer as they share the voltage, whereas in parallel each bulb receives the full battery voltage.
在串联电路中，电流只有一条完整的路径。如果一个元件损坏，整个电路停止工作。串联电路各处的电流相等。在并联电路中，元件连接在分开的支路上，每条支路为电流提供独立的路径。如果一条支路断开，电流仍可通过其他支路。串联增加更多灯泡会使其变暗，因为它们分担电压；而在并联电路中，每个灯泡都获得电池的全部电压。
10. Light and Sound | 光与声
bjects because light from a source reflects off them and enters our eyes. The law of reflection states that the angle of incidence (i) equals the angle of reflection (r), measured from a line perpendicular to the surface (the normal).
光是一种能量形式，在真空中以大约 3 × 10⁸ 米/秒的速度沿直线传播。我们看见物体是因为光源发出的光从物体表面反射进入我们的眼睛。反射定律指出，入射角（i）等于反射角（r），这两个角都是相对于垂直于表面的线（法线）测量的。
Refraction occurs when light passes from one transparent medium to another, causing it to change speed and bend. For example, light slows down and bends towards the normal when entering glass from air. A convex lens can converge light rays to a focal point, forming images.
折射发生在光从一种透明介质进入另一种介质时，光速改变并发生弯曲。例如，光从空气进入玻璃时会减慢并弯向法线。凸透镜能将光线会聚到焦点，形成像。
Sound is produced by vibrating objects and travels as longitudinal waves. Sound needs a medium (solid, liquid or gas) to travel through; it cannot travel through a vacuum. The speed of sound in air is about 340 m/s. Pitch is determined by frequency (number of vibrations per second, measured in hertz, Hz): higher frequency gives a higher pitch. Loudness depends on the amplitude of the vibration: larger amplitude produces a louder sound.
声音由振动的物体产生，以纵波形式传播。声音需要介质（固体、液体或气体）传播，不能在真空中传播。声音在空气中的速度约为 340 米/秒。音调由频率（每秒振动次数，单位为赫兹 Hz）决定：频率越高，音调越高。响度取决于振幅：振幅越大，声音越响。
11. Earth Science: Rocks and the Solar System | 地球科学：岩石与太阳系
The Earth is made up of different types of rocks, classified by how they were formed. Igneous rocks, such as granite and basalt, form from cooled magma or lava. Sedimentary rocks, like sandstone and limestone, are formed from layers of sediment compacted and cemented together over millions of years; they often contain fossils. Metamorphic rocks, such as marble and slate, are formed when existing rocks are changed by heat and pressure.
地球由不同类型的岩石组成，按形成方式分类。岩浆岩（如花岗岩和玄武岩）由冷却的岩浆或熔岩形成。沉积岩（如砂岩和石灰岩）由沉积物层经过数百万年的压实和胶结而成；它们常含有化石。变质岩（如大理岩和板岩）由原有岩石在热和压力作用下变质而成。
The rock cycle describes how rocks can change from one type to another over geological time. Weathering breaks down rocks into smaller pieces; erosion transports these fragments; deposition lays them down. Heat and pressure can turn sedimentary rock into metamorphic rock, and melting followed by cooling creates igneous rock.
岩石循环描述了在地质时期中岩石如何从一种类型转变为另一种类型。风化将岩石分解成更小的碎屑；侵蚀搬运这些碎屑；沉积将它们堆积。热和压力可将沉积岩转变为变质岩，而熔融后再冷却则形成岩浆岩。
Our solar system consists of the Sun at the centre, with eight planets orbiting it. The inner planets (Mercury, Venus, Earth, Mars) are rocky, while the outer planets (Jupiter, Saturn, Uranus, Neptune) are gas giants. The Earth orbits the Sun once every 365¼ days, causing the seasons, and rotates on its axis once every 24 hours, causing day and night. The Moon is a natural satellite that orbits Earth, and its phases are caused by the changing relative positions of the Earth, Moon and Sun.
我们的太阳系以太阳为中心，有八大行星围绕它运行。内行星（水星、金星、地球、火星）是岩石行星，而外行星（木星、土星、天王星、海王星）是气态巨行星。地球绕太阳公转一周需 365¼ 天，产生四季；绕地轴自转一周需 24 小时，产生昼夜。月球是绕地球运转的天然卫星，其相位变化由地球、月球和太阳相对位置的改变引起。
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