📚 Year 7 OCR Science: Core Knowledge Review | Year 7 OCR 科学：核心知识点梳理
Year 7 OCR Science lays the foundations for understanding the natural world through biology, chemistry, and physics. This article revisits the essential topics you will encounter, from the building blocks of life to the forces that shape the universe. Each concept is explained clearly and paired with Chinese explanations to strengthen your bilingual scientific literacy and help you excel in your studies.
Year 7 OCR 科学课程从生物、化学和物理三个维度为你搭建理解自然世界的基石。本文带你重温那些一定会学到的核心知识点，从生命的构造单元到塑造宇宙的力，逐一梳理。每个概念都用清晰的中英双语对照讲解，帮助你在提升双语科学素养的同时，轻松应对学习挑战。
1. Cells – The Building Blocks of Life | 细胞——生命的基石
All living organisms are made of cells. Cells are the smallest units that can perform all life processes, such as movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition (MRS GREN).
所有生物体都由细胞构成。细胞是能够执行全部生命过程的最小单位，这些过程包括运动、呼吸、感应、生长、繁殖、排泄和营养（可用 MRS GREN 记忆）。
Animal cells contain a cell membrane, cytoplasm, and a nucleus. Plant cells have these three parts plus a rigid cell wall, a large central vacuole, and chloroplasts for photosynthesis.
动物细胞具备细胞膜、细胞质和细胞核。植物细胞除了这三部分外，还具有坚硬的细胞壁、一个中央大液泡以及用于光合作用的叶绿体。
Specialised cells such as red blood cells, nerve cells, and root hair cells have adapted structures that help them carry out specific functions efficiently.
特化细胞（如红细胞、神经细胞和根毛细胞）具有适应特定功能的结构，使它们能高效地完成专门任务。
2. Body Systems and Reproduction | 人体系统与生殖
The human body is organised into levels: cells → tissues → organs → organ systems. For example, muscle cells form muscle tissue, which makes up the stomach, an organ of the digestive system.
人体具有结构层次：细胞 → 组织 → 器官 → 器官系统。例如，肌肉细胞构成肌肉组织，肌肉组织构成胃这个消化系统的器官。
Key organ systems include the digestive system (breaking down food), the respiratory system (gas exchange in the lungs), and the circulatory system (transporting substances via blood). The skeletal and muscular systems work together to enable movement.
重要的器官系统包括消化系统（分解食物）、呼吸系统（在肺部进行气体交换）和循环系统（通过血液运输物质）。骨骼系统与肌肉系统协同工作，实现运动。
Reproduction ensures the continuation of a species. In humans, the male and female reproductive systems produce sperm and egg cells, which fuse during fertilisation to form a zygote. In plants, pollination leads to fertilisation inside the ovary, resulting in seeds.
生殖确保物种的延续。人类生殖系统中，男性和女性分别产生精子和卵细胞，两者在受精过程中结合形成受精卵。在植物中，传粉后子房内发生受精，最终形成种子。
3. States of Matter and the Particle Model | 物质状态与粒子模型
All matter exists as solid, liquid, or gas. The particle model explains the properties of each state: solids have a fixed shape and volume with particles tightly packed in a regular pattern; liquids have a fixed volume but take the shape of their container, with particles touching but moving past one another; gases have no fixed shape or volume, with particles moving rapidly and far apart.
所有物质以固态、液态或气态存在。粒子模型解释了每种状态的性质：固体有固定的形状和体积，粒子紧密排列成规则模式；液体有固定的体积但形状随容器而变，粒子相互接触但可相对滑动；气体既无固定形状也无固定体积，粒子快速运动且相距很远。
Changes of state—melting, freezing, boiling, condensing, sublimating—occur when energy is added or removed, breaking or forming inter‑particle attractions without changing the particles themselves.
物质的状态变化——熔化、凝固、沸腾、冷凝、升华——发生在能量增加或减少时，会打破或形成粒子间的吸引力，但不会改变粒子本身。
Diffusion is the movement of particles from an area of high concentration to low concentration. This can be demonstrated by the spread of perfume or ink in water, and it happens because particles are always in random motion.
扩散是指粒子从高浓度区域向低浓度区域的运动。香水的扩散、墨水在水中的扩散都能证明这一点，扩散之所以发生，是因为粒子始终在做无规则运动。
4. Atoms, Elements, and Compounds | 原子、元素与化合物
An element is a substance made of only one type of atom. There are about 100 elements, displayed in the Periodic Table. Each element has a chemical symbol, such as O for oxygen and Fe for iron.
元素是只由一种原子组成的物质。目前已知大约有 100 种元素，它们被排列在元素周期表中。每种元素都有一个化学符号，例如氧是 O，铁是 Fe。
Atoms have a small central nucleus containing protons and neutrons, surrounded by electrons. The number of protons determines the element’s identity (atomic number).
原子具有一个微小的中心原子核，核内包含质子和中子，外围是运动的电子。质子的数量决定了元素的种类（即原子序数）。
When two or more elements chemically bond, they form a compound. Compounds have different properties from their constituent elements. For example, sodium is a reactive metal and chlorine is a poisonous gas, yet sodium chloride is harmless table salt.
当两种或多种元素通过化学键结合时，就形成了化合物。化合物的性质与组成它的元素完全不同。例如，钠是一种活泼金属，氯气是一种有毒气体，但氯化钠却是安全的食盐。
Chemical formulae represent compounds using symbols and subscript numbers, such as H₂O (water) and CO₂ (carbon dioxide). The subscript number shows how many atoms of that element are in one unit of the compound.
化学式用符号和下标数字来表示化合物，例如 H₂O（水）和 CO₂（二氧化碳）。下标数字表示该元素在一个化合物单元中的原子个数。
5. Chemical Reactions | 化学反应
A chemical reaction involves the rearrangement of atoms to form new substances. Signs of a reaction include colour change, temperature change, gas production (bubbles or fizzing), and the formation of a precipitate (a solid from two liquids).
化学反应涉及原子的重新排列，从而生成新的物质。化学反应的迹象包括颜色变化、温度变化、产生气体（气泡或嘶嘶声）以及沉淀的生成（两种液体混合后产生固体）。
In a chemical reaction, the total mass stays the same; this is the law of conservation of mass. The atoms in the reactants are simply rearranged to form the products. Word equations describe a reaction, for instance:
magnesium + oxygen → magnesium oxide
在化学反应中，总质量保持不变，这就是质量守恒定律。反应物中的原子只不过重新排列形成了生成物。可以用文字方程式来描述反应，例如：镁 + 氧气 → 氧化镁。
Combustion is a reaction with oxygen that releases heat and light. Rusting is the slow reaction of iron with oxygen and water, forming hydrated iron oxide. Acids react with alkalis in neutralisation to produce salt and water.
燃烧是一种与氧气发生反应、释放热量和光的过程。生锈是铁与氧气、水缓慢反应生成水合氧化铁的过程。酸与碱发生中和反应生成盐和水。
6. Forces and Motion | 力与运动
A force is a push or pull on an object, measured in newtons (N). Forces can change an object’s speed, direction, or shape. Contact forces, such as friction, occur when two objects touch; non‑contact forces, like gravity and magnetism, act at a distance.
力是对物体的推或拉，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（如摩擦力）在两物体接触时产生；非接触力（如重力和磁力）可以在一定距离外作用。
Balanced forces result in no change in motion (constant speed or stationary), whereas unbalanced forces cause acceleration or deceleration. The overall force acting on an object is called the resultant force.
平衡力不会改变运动状态（保持匀速或静止），而非平衡力则会引起加速或减速。作用在物体上的总力称为合力。
Speed is a measure of how quickly an object moves. The relationship between speed, distance, and time is given by the formula:
speed = distance ÷ time
速度用来衡量物体运动的快慢。速度、距离和时间之间的关系由公式表示：速度 = 距离 ÷ 时间。
Hooke’s Law describes the extension of a spring: the extension is proportional to the force applied, up to a limit. This can be written as:
F = k × e
where F is the force in newtons, e is the extension in metres, and k is the spring constant. Weight is the force of gravity on a mass: weight (N) = mass (kg) × gravitational field strength (N/kg).
胡克定律描述了弹簧的伸长量：在弹性限度内，伸长量与施加的力成正比。可以表示为 F = k × e，其中 F 是力（N），e 是伸长量（m），k 是弹簧常数。重量是物体所受重力的大小：重量（N）= 质量（kg）× 重力场强度（N/kg）。
7. Energy Transfers and Resources | 能量传递与资源
Energy is the ability to do work and is measured in joules (J). It exists in many forms: kinetic, thermal, chemical, gravitational potential, elastic potential, light, sound, and electrical.
能量是做功的本领，以焦耳（J）为单位。能量有多种形式：动能、热能、化学能、重力势能、弹性势能、光能、声能和电能。
Energy cannot be created or destroyed; it can only be transferred or transformed from one type to another. For example, a lamp transforms electrical energy into light and heat. Energy transfer diagrams (Sankey diagrams) help visualise useful and wasted energy.
能量不能被创造或消灭，只能被转移或从一种形式转化为另一种形式。例如，电灯把电能转化为光能和热能。能量转移图（桑基图）可以帮助我们直观看到有用能量和浪费的能量。
Fuels and food are stores of chemical energy. Renewable resources (solar, wind, tidal, biomass) can be replenished quickly, while non‑renewable resources (coal, oil, natural gas) are finite and release carbon dioxide when burned, contributing to climate change.
燃料和食物是化学能的储存库。可再生资源（太阳能、风能、潮汐能、生物质能）可以在短时间内再生，而非可再生资源（煤、石油、天然气）是有限的，燃烧时会释放二氧化碳，加剧气候变化。
8. Waves: Sound and Light | 波：声音和光
Sound is produced by vibrations and travels as longitudinal waves through a medium (solid, liquid, or gas). It cannot travel through a vacuum. The speed of sound in air is approximately 340 m/s, but it travels faster in solids and liquids.
声音由振动产生，以纵波的形式通过介质（固体、液体或气体）传播。声音不能在真空中传播。声音在空气中的速度约为 340 m/s，但在固体和液体中传播得更快。
The amplitude of a sound wave determines its loudness; a larger amplitude means a louder sound. The frequency (number of vibrations per second, measured in hertz, Hz) determines pitch; a higher frequency gives a higher pitch.
声波的振幅决定了声音的大小；振幅越大，声音越响。频率（每秒振动次数，单位为赫兹 Hz）决定音调的高低；频率越高，音调越高。
Light travels much faster than sound (about 300,000 km/s in a vacuum) and moves in straight lines. When light hits a surface it can be reflected, refracted (bent), or absorbed. Reflection explains how we see non‑luminous objects, and refraction causes phenomena like a pencil appearing bent in water.
光的传播速度比声音快得多（真空中约 300,000 km/s），且沿直线传播。当光照射到物体表面时，可以被反射、折射（弯曲）或吸收。反射解释了我们如何看见不发光的物体，折射则解释了铅笔在水中看起来弯曲等现象。
White light can be split into the colours of the spectrum (red, orange, yellow, green, blue, indigo, violet) by a prism or water droplets, producing a rainbow. Coloured filters let only certain colours of light through, while coloured objects reflect certain colours and absorb others.
白光可以被棱镜或水滴分解成光谱的颜色（红、橙、黄、绿、蓝、靛、紫），形成彩虹。彩色滤光片只允许特定颜色的光通过，而彩色物体则反射某些颜色的光并吸收其他颜色。
9. Electricity and Magnetism | 电与磁
An electric circuit needs a complete loop for current to flow. Current (amperes, A) is the rate of flow of electric charge, and voltage (volts, V) is the energy transferred per unit charge. A simple circuit contains a cell, wires, and a component such as a bulb or motor.
电路需要一个完整的回路，电流才能流动。电流（安培 A）是电荷流动的速率，而电压（伏特 V）是单位电荷转移的能量。一个简单电路包含电池、导线以及一个用电器，比如灯泡或马达。
Components can be connected in series (one path for current) or in parallel (multiple paths). In a series circuit the current is the same everywhere, but in a parallel circuit the currents in the branches add up to the total current.
电路元件可以串联（电流只有一条通路）或并联（多条通路）。在串联电路中，各处电流相等；而在并联电路中，各支路电流之和等于总电流。
Conductors such as copper allow current to pass easily due to free electrons, while insulators such as plastic block current flow. Magnetic materials like iron, cobalt, and nickel are attracted to magnets. A bar magnet has a north and south pole; like poles repel, unlike poles attract.
铜等导体由于拥有自由电子，能让电流轻易通过；而塑料等绝缘体则阻止电流流动。铁、钴、镍等磁性材料会被磁铁吸引。条形磁铁有南北两个磁极；同极相斥，异极相吸。
Electromagnets are created by passing current through a coil of wire wrapped around an iron core. The strength of an electromagnet can be increased by increasing the current, adding more turns to the coil, or using a soft iron core.
电磁铁通过使电流流过绕在铁芯上的线圈来制造。增大电流、增加线圈匝数或使用软铁芯都可以增强电磁铁的磁力。
10. Earth Structure and Rocks | 地球结构与岩石
The Earth is made of four main layers: the solid inner core (iron and nickel), the liquid outer core, the thick semi‑solid mantle, and the thin outer crust, which supports all life.
地球由四个主要圈层构成：固态的内核（铁和镍）、液态的外核、厚实的半固态地幔以及支撑所有生命的薄薄地壳。
There are three main rock types. Igneous rocks, such as granite and basalt, form from cooled magma or lava. Sedimentary rocks, like sandstone and limestone, are made of compacted sediments and often contain fossils. Metamorphic rocks, such as marble and slate, are formed when existing rocks are changed by heat and pressure.
岩石主要有三大类。火成岩（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）由压实的沉积物构成，通常含有化石。变质岩（如大理石和板岩）是在热和压力的作用下由原有岩石变质而成的。
The rock cycle shows how rocks continuously change from one type to another over geological time, driven by processes like weathering, erosion, melting, and uplift.
岩石循环展示了在风化、侵蚀、熔融和隆升等地质过程驱动下，岩石如何在地质时间尺度上不断地从一种类型转变为另一种类型。
11. The Solar System and Beyond | 太阳系及更远
Our Solar System consists of one star, the Sun, and everything that orbits it: eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), their moons, dwarf planets, asteroids, and comets.
我们的太阳系由一颗恒星——太阳，以及围绕它运行的一切组成：八大行星（水星、金星、地球、火星、木星、土星、天王星、海王星）、它们的卫星、矮行星、小行星和彗星。
Gravity keeps the planets in orbit around the Sun. The closer a planet is to the Sun, the shorter its orbital period. Earth takes 365 ¼ days to complete one orbit, which defines a year, while its rotation on its axis in 24 hours defines a day.
万有引力使行星保持在绕太阳运行的轨道上。行星离太阳越近，公转周期越短。地球绕太阳一周需要 365 ¼ 天，这定义了一年的长度；而它绕地轴自转一周需 24 小时，定义了一天的长度。
The Moon orbits Earth every 28 days, causing the phases of the moon we see from Earth. Eclipses occur when the Sun, Earth, and Moon align: a solar eclipse when the Moon passes between the Sun and Earth, and a lunar eclipse when Earth comes between the Sun and the Moon.
月球每 28 天绕地球一周，这就产生了我们在地球上看到的月相变化。当太阳、地球和月球排成一条直线时会发生食相：月球走到太阳和地球之间时出现日食，地球走到太阳和月球之间时出现月食。
Beyond our Solar System, stars form galaxies. Our Sun is one of billions of stars in the Milky Way galaxy. The Universe contains billions of galaxies, and scientists use light years to measure the vast distances between them.
在太阳系之外，恒星汇聚成星系。太阳只是银河系数千亿颗恒星中的一颗。宇宙包含着数十亿个星系，科学家用光年来度量它们之间的巨大距离。
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