📚 Year 8 WJEC Science: Core Knowledge Review | Year 8 WJEC 科学：核心知识点梳理
In Year 8 WJEC Science, you build on the foundations from Year 7 and explore key ideas across biology, chemistry and physics. This article brings together the most important core knowledge you need to understand, whether you're revising for a test or simply keeping your science sharp.
在 Year 8 WJEC 科学课程中，你在七年级的基础上进一步探索生物、化学和物理的核心概念。本文为你梳理了最需要掌握的核心知识点，无论你是在备考还是想巩固科学基础，都能派上用场。
1. Cells and Living Organisms | 细胞与生物体
All living organisms are composed of cells, the basic building blocks that carry out essential life processes.
所有生物体都由细胞构成，细胞是执行基本生命过程的基础单元。
Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria, which release energy through respiration.
动物细胞包含细胞核、细胞质、细胞膜和线粒体，线粒体通过呼吸作用释放能量。
Plant cells have the same parts plus a rigid cell wall, a large permanent vacuole and chloroplasts that trap light for photosynthesis.
植物细胞除了这些结构，还有坚硬的细胞壁、一个大型永久液泡以及捕获光能进行光合作用的叶绿体。
Cells group together to form tissues, tissues form organs, and organs work together in organ systems, such as the digestive system.
细胞聚集形成组织，组织构成器官，器官协同工作组成器官系统，比如消化系统。
2. Reproduction and Genetics | 生殖与遗传
Sexual reproduction involves the fusion of male and female gametes (sperm and egg) to produce a fertilised egg, which develops into a unique offspring.
有性生殖涉及雄性和雌性配子（精子和卵子）融合形成受精卵，受精卵发育成具有独特特征的后代。
Asexual reproduction produces genetically identical offspring, or clones, from a single parent, as seen in strawberry runners and potato tubers.
无性生殖由单一亲本产生基因相同的后代即克隆，例如草莓的匍匐茎和马铃薯的块茎繁殖。
DNA is the molecule that carries genetic information, organised into structures called chromosomes; a gene is a short section of DNA that codes for a characteristic.
DNA 是携带遗传信息的分子，组装成称为染色体的结构；基因是 DNA 上编码某个特征的一小段。
Inherited traits, such as eye colour, are passed from parents to offspring, while variation within a species can also be influenced by the environment.
眼睛颜色等遗传性状由亲代传给子代，而物种内的变异也可能受到环境的影响。
3. Ecosystems and Food Webs | 生态系统与食物网
An ecosystem is made up of a community of living organisms interacting with their non-living environment, including factors like temperature and light.
生态系统由生物群落与其非生物环境相互作用而构成，包括温度和光照等因素。
Food chains show the flow of energy from one organism to another; arrows always point from the food to the feeder.
食物链显示能量从一个生物体流向另一个生物体的方向；箭头总是从食物指向取食者。
Producers (plants and algae) make their own food by photosynthesis, primary consumers eat producers, and secondary consumers eat primary consumers.
生产者（植物和藻类）通过光合作用制造食物，初级消费者取食生产者，次级消费者取食初级消费者。
Food webs are networks of interconnected food chains, showing that most organisms eat more than one type of food.
食物网是相互连接的食物链组成的网络，表明大多数生物不止吃一种食物。
Decomposers such as bacteria and fungi break down dead material, recycling nutrients back into the soil.
分解者如细菌和真菌分解死去的生物，将营养物质循环回土壤中。
4. Atoms, Elements and Compounds | 原子、元素与化合物
All materials are made of tiny particles called atoms; an element is a substance made of only one type of atom.
所有物质都由称为原子的微小粒子组成；元素是仅由一种原子组成的纯物质。
Atoms consist of a central nucleus containing protons and neutrons, surrounded by electrons moving in shells.
原子由原子核（包含质子和中子）以及核外分层运动的电子构成。
A compound is formed when two or more different elements chemically combine in fixed proportions, for example, water (H₂O).
化合物是由两种或多种不同元素以固定比例化学结合而成的物质，例如水 (H₂O)。
Chemical symbols represent elements (e.g. C for carbon), and chemical formulas show the types and numbers of atoms in a compound (e.g. CO₂).
化学符号表示元素（如 C 代表碳），化学式则显示化合物中原子的种类和数目（如 CO₂）。
5. Chemical Reactions | 化学反应
In a chemical reaction, reactants are transformed into new products; the total mass does not change (conservation of mass).
在化学反应中，反应物转变为新的产物；总质量保持不变（质量守恒）。
Signs of a reaction include colour change, fizzing or gas production, a temperature change, or a precipitate forming.
化学反应的迹象包括颜色变化、气泡或气体的产生、温度变化或沉淀的形成。
2Mg + O₂ → 2MgO
镁和氧气反应生成氧化镁
Exothermic reactions release energy to the surroundings, usually as heat; endothermic reactions absorb energy, causing a drop in temperature.
放热反应向周围环境释放能量（通常是热能）；吸热反应则吸收能量，导致温度降低。
Acids react with alkalis in a neutralisation reaction, producing a salt and water; common acids include hydrochloric acid (HCl).
酸和碱发生中和反应生成盐和水；常见的酸包括盐酸 (HCl)。
6. The Periodic Table | 元素周期表
The periodic table organises all known elements in order of increasing atomic number and groups elements with similar properties into vertical columns.
元素周期表按原子序数递增的顺序排列所有已知元素，并将性质相似的元素归入同一纵列。
Rows are called periods; as you move across a period, the elements change from metallic to non-metallic character.
横行称为周期；从左到右，元素的金属性逐渐减弱，非金属性增强。
Group 1 elements are the alkali metals, very reactive with water; Group 7 elements are halogens, reactive non-metals; Group 0 contains the unreactive noble gases.
第 1 族是碱金属，与水反应剧烈；第 7 族是卤素，活泼的非金属；第 0 族包含不活泼的稀有气体。
Metals are found on the left and centre, and are typically shiny, good conductors, and malleable; non-metals are on the right and are often dull and brittle.
金属位于左侧和中部，通常有光泽、导热导电、具有延展性；非金属在右侧，往往暗淡且易碎。
7. Forces and Motion | 力与运动
A force is a push or a pull, measured in newtons (N), and can change an object's speed, direction or shape.
力是推或拉的作用，单位为牛顿 (N)，可以改变物体的速度、方向或形状。
When forces on an object are balanced, it remains stationary or continues to move at a constant speed in a straight line.
当作用在物体上的力平衡时，物体保持静止或沿直线匀速运动。
Friction is a force that opposes motion between two surfaces in contact; air resistance is a type of friction acting through the air.
摩擦力是阻碍两个接触面之间相对运动的力；空气阻力是物体在空气中运动时受到的摩擦力。
Speed is calculated as distance divided by time; the equation is:
速度等于距离除以时间；计算公式为：
speed = distance / time
Distance–time graphs show how far an object has travelled over time; a steeper line indicates a higher speed, while a horizontal line means the object is stationary.
距离–时间图显示物体随时间移动的距离；斜率越大表示速度越快，水平线段则表示物体静止。
8. Energy Transfers and Resources | 能量转移与能源
Energy exists in many forms, including kinetic, thermal, light, sound, electrical, and gravitational potential energy.
能量有多种形式，包括动能、热能、光能、声能、电能和重力势能。
Energy can be transferred from one store to another or from one object to another, but it is never created or destroyed — this is the principle of conservation of energy.
能量可以从一个储存器转移到另一个，或从一个物体转移到另一物体，但既不能被创造也不会被消灭 —— 这就是能量守恒定律。
In any energy transfer, some energy always spreads out to the surroundings as less useful thermal energy, often called dissipated energy.
在任何能量转移过程中，总会有部分能量以不太有用的热能形式散失到环境中，通常称为耗散能。
Renewable energy resources (e.g. solar, wind, hydroelectric) are replenished naturally, whereas non-renewable resources (e.g. coal, oil, natural gas) are finite and release carbon dioxide when burned.
可再生能源（如太阳能、风能、水力发电）可以自然补充，而非可再生能源（如煤、石油、天然气）储量有限，燃烧时会释放二氧化碳。
9. Electricity and Magnetism | 电与磁
Electric current is the flow of electric charge, usually carried by electrons moving through a conductor; current is measured in amperes (A).
电流是电荷的流动，通常由电子在导体中移动形成；电流的单位是安培 (A)。
Voltage (or potential difference) is the push that drives the current around a circuit, measured in volts (V); resistance opposes the flow and is measured in ohms (Ω).
电压（电势差）是驱动电流在电路中流动的推动力，单位为伏特 (V)；电阻阻碍电流流动，单位为欧姆 (Ω)。
In a series circuit, current is the same through all components, whereas in a parallel circuit the current splits but the voltage across each branch is the same.
在串联电路中，通过所有元件的电流相等；在并联电路中，总电流分流，但各支路两端的电压相等。
Magnetic materials (e.g. iron, cobalt, nickel) are attracted to magnets; an electromagnet is created by passing a current through a coil of wire wrapped around an iron core.
磁性材料（如铁、钴、镍）会被磁铁吸引；电磁铁是通过在铁芯周围缠绕线圈并通入电流而产生的磁性装置。
10. Waves: Sound and Light | 波：声与光
Sound travels as a longitudinal wave, where particles vibrate parallel to the direction of the wave; sound cannot travel through a vacuum because there are no particles to vibrate.
声音以纵波的形式传播，粒子振动方向与波的传播方向平行；声音不能在真空中传播，因为没有振动的粒子。
The loudness of a sound depends on the amplitude of the wave; the pitch depends on its frequency, measured in hertz (Hz).
声音的响度取决于波的振幅；音调高低取决于波的频率，频率单位是赫兹 (Hz)。
Light travels in straight lines and is a transverse wave; we see objects because light reflects off them into our eyes.
光沿直线传播，属于横波；我们看到物体是因为光从物体反射进入我们的眼睛。
Reflection obeys the law: the angle of incidence equals the angle of reflection, measured from the normal.
光的反射遵循反射定律：入射角等于反射角，这两个角都是从法线开始测量的。
White light is made up of a spectrum of colours (red, orange, yellow, green, blue, indigo, violet), which can be separated by refraction through a prism.
白光由红、橙、黄、绿、蓝、靛、紫等色光组成，通过棱镜的折射可以将它们分开。
11. Earth and Space | 地球与太空
The Earth has a layered structure: a thin crust, a semi-solid mantle, a liquid outer core, and a solid inner core.
地球具有圈层结构：薄薄的地壳、半固态的地幔、液态的外核和固态的内核。
The rock cycle describes how igneous, sedimentary and metamorphic rocks are constantly recycled: igneous rocks form from cooled magma, sedimentary rocks from compacted layers of sediment, and metamorphic rocks from heat and pressure changing existing rocks.
岩石循环描述了火成岩、沉积岩和变质岩如何不断转化：火成岩由岩浆冷却形成，沉积岩由沉积物压实胶结而成，变质岩是原有岩石在高温高压下变质形成的。
The Solar System consists of the Sun, eight planets and their moons, dwarf planets, asteroids and comets; the order of planets from the Sun is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
太阳系由太阳、八大行星及其卫星、矮行星、小行星和彗星组成；距太阳由近到远的行星顺序为水星、金星、地球、火星、木星、土星、天王星和海王星。
The Earth's rotation on its axis causes day and night; its orbit around the Sun, combined with the tilt of its axis, causes the seasons.
地球绕地轴自转产生了昼夜交替；地球绕太阳公转，加上地轴的倾斜，导致了四季变化。
The phases of the Moon are caused by the Moon's orbit around Earth, changing how much of the sunlit side we can see.
月相的变化是由于月球绕地球公转，使得我们看到的被太阳照亮的部分发生变化。
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