📚 Year 7 OCR Physics: Core Knowledge Review | Year 7 OCR 物理：核心知识点梳理
Welcome to your essential Year 7 OCR Physics revision guide. This article walks you through the core topics you will encounter at Key Stage 3, from energy stores and forces to electricity, waves, particle theory, and space. Each section presents the key ideas in plain English and Chinese, helping you master both the concepts and the subject vocabulary. Read on to build confidence for class tests and end-of-year assessments.
欢迎来到 Year 7 OCR 物理核心知识点梳理。本文将带你系统地回顾 Key Stage 3 阶段的关键物理概念，包括能量类型与转移、力与运动、电学、波、粒子模型与太空。每个小节都以中英双语呈现要点，帮助你同时掌握概念和学科术语，为课堂测验和年末考试做好充分准备。
1. Energy Types and Energy Transfer | 能量类型与能量转移
Energy exists in different forms and can be stored or transferred. In Year 7 science, we identify energy stores such as kinetic, thermal, chemical, gravitational potential, elastic potential, and nuclear energy. Energy can be transferred by heating, by doing mechanical work, or by radiation such as light and sound.
能量以多种形式存在，可以被储存或转移。在七年级科学中，我们学习到的能量储存形式有动能、热能、化学能、重力势能、弹性势能和核能。能量可以通过加热、做机械功或通过光与声等辐射方式进行转移。
The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another. When you switch on a lamp, electrical energy is transferred into light and thermal energy. Similarly, a moving car has kinetic energy that was originally chemical energy from the fuel.
能量守恒定律指出，能量不能被创造或消灭，只能从一种储存形式转移为另一种。当你打开台灯时，电能被转移为光能和热能。同样，行驶的汽车具有的动能最初来自燃料中的化学能。
We often represent energy transfers using Sankey diagrams, where the width of arrows shows how much energy is useful and how much is wasted. In all real processes, some energy is always dissipated as thermal energy, which spreads out into the surroundings and is no longer useful.
我们常用桑基图来表示能量转移，箭头宽度显示有用能量和被浪费的能量。在所有真实过程中，总会有一部分能量以热能的形式耗散，扩散到周围环境中，无法再被利用。
2. Forces and Motion | 力与运动
A force is a push or a pull that can change the shape, speed, or direction of an object. Forces are measured in newtons (N). They can be contact forces, such as friction and tension, or non-contact forces, such as gravity, magnetism, and electrostatic force.
力是推或拉的作用，可以改变物体的形状、速度或运动方向。力的单位是牛顿（N）。力可以是接触力，如摩擦力和拉力；也可以是非接触力，如重力、磁力和静电力。
When multiple forces act on an object, we can find the resultant force. If forces are balanced, the object remains at rest or continues moving at a steady speed. If forces are unbalanced, the object will accelerate or decelerate, meaning its speed or direction changes.
当多个力作用在一个物体上时，我们可以求出合力。如果力是平衡的，物体会保持静止或匀速直线运动；如果力不平衡，物体就会加速或减速，即速度或方向发生改变。
Friction is a force that opposes motion. It can be useful, like when we walk or brake a bicycle, but it can also cause unwanted energy loss as heat. Air resistance and water resistance are types of friction that slow objects down when they move through fluids.
摩擦力是一种阻碍运动的力。它有时很有用，比如走路或刹自行车时；但它也会将能量转化为热能，造成不希望的能量损失。空气阻力和水阻力是物体在流体中运动时遇到的摩擦力，会使物体减速。
3. Speed and Acceleration | 速度与加速度
Speed tells us how fast an object is moving. It is calculated using the equation:
Speed = Distance ÷ Time
In symbols, we often write v = d ÷ t. The unit of speed is metres per second (m/s), but we also use kilometres per hour (km/h) or miles per hour (mph) in everyday life.
速度表示物体运动的快慢，可使用以下公式计算：
速度 = 距离 ÷ 时间
用符号通常是 v = d ÷ t。速度的单位是米每秒（m/s），日常生活中也常用千米每小时（km/h）或英里每小时（mph）。
5 s = 4 m/s². Negative acceleration means slowing down, which is also called deceleration.
加速度描述物体速度变化的快慢。如果一辆汽车在 5 秒内从静止加速到 20 m/s，其加速度为 (20 m/s) ÷ 5 s = 4 m/s²。负加速度表示减速，也称为减速度。
Distance–time graphs show how far an object has travelled over time. A straight, sloping line means constant speed, while a horizontal line means the object is stationary. The steeper the slope, the greater the speed.
距离–时间图显示物体随时间移动的距离。一条倾斜的直线表示匀速运动，水平线表示物体静止。斜率越大，速度越快。
4. Electricity and Circuits | 电与电路
An electric circuit provides a complete path for electric current to flow. For a circuit to work, it must include a power source (such as a cell or battery), wires, and a load (such as a bulb or motor). Current is the flow of electric charges, measured in amperes (A).
电路为电流提供了一条完整的通路。要使电路工作，必须包含电源（如电池）、导线和负载（如灯泡或马达）。电流是电荷的流动，单位是安培（A）。
Voltage (or potential difference) is the push that drives current around a circuit, measured in volts (V). Resistance opposes the flow of current and is measured in ohms (Ω). These three are linked by Ohm’s law:
Voltage = Current × Resistance (V = I × R)
电压（又称电位差）是推动电流流动的“推力”，单位是伏特（V）。电阻阻碍电流流动，单位是欧姆（Ω）。这三者由欧姆定律联系在一起：
电压 = 电流 × 电阻 (V = I × R)
In a series circuit, components are connected one after another, so the current is the same everywhere but the voltage is shared. In a parallel circuit, each component has its own branch; the voltage across each branch is the same, but the current splits between them.
在串联电路中，元件依次连接，因此各处电流相同，但电压被分配。在并联电路中，每个元件有自己的支路，各支路两端电压相同，而电流分开流过各支路。
Always treat electricity with care. Never experiment with mains sockets, and make sure your hands are dry when handling batteries. Use insulated wires and avoid short circuits that can cause overheating.
始终要安全用电。不要用家里的插座做实验，操作电池时双手保持干燥。使用绝缘导线，避免短路导致过热。
5. Waves: Sound and Light | 波：声音与光
Waves transfer energy from one place to another without transferring matter. In Year 7, we learn about two main wave types: transverse waves (like light and water ripples) and longitudinal waves (like sound). In a transverse wave, the vibrations are perpendicular to the direction of energy travel; in a longitudinal wave, they are parallel.
波将能量从一处传递到另一处，但不传递物质。在七年级，我们主要学习两种波：横波（如光波和水波）和纵波（如声波）。横波的振动方向与能量传播方向垂直；纵波的振动方向与能量传播方向平行。
Sound is produced by vibrating objects and travels as a longitudinal wave. It needs a medium (solid, liquid, or gas) to travel through, which is why there is no sound in space. The speed of sound in air is about 340 m/s, far slower than the speed of light (300 000 000 m/s).
声音由物体振动产生，以纵波形式传播。它需要通过介质（固体、液体或气体）传播，所以太空中没有声音。空气中声速约为 340 m/s，远小于光速（3×10⁸ m/s）。
Light travels in straight lines and can be reflected by mirrors and refracted when it passes from one transparent material to another. The law of reflection states that the angle of incidence equals the angle of reflection. White light can be split into a spectrum of colours using a prism, which is called dispersion.
光沿直线传播，可以被镜子反射，也可以在穿过不同透明介质时发生折射。反射定律指出，入射角等于反射角。白光通过棱镜可以被分解为七色光谱，这种现象称为色散。
6. The Particle Model and States of Matter | 粒子模型与物质状态
All matter is made up of tiny particles. The particle model helps explain the properties of solids, liquids, and gases. In solids, particles are packed closely in a regular pattern, vibrating in fixed positions. In liquids, particles are still close together but can move past each other. In gases, particles are far apart and move randomly at high speed.
所有物质都由微小粒子组成。粒子模型有助于解释固体、液体和气体的性质。固体中，粒子紧密排列在固定位置，只能在原地振动。液体中，粒子仍然相互靠近，但可以相对滑动。气体中，粒子相距很远，高速无规则运动。
Changes between states can be explained by the energy of particles. Heating gives particles more kinetic energy, causing them to move faster or break free from their fixed positions. Cooling removes energy, making particles move less and attractions pull them closer together.
物态变化可以用粒子的能量解释。加热后粒子获得更多动能，运动加快或摆脱固定位置；冷却则使粒子能量减少，运动减缓，引力将它们拉得更近。
Diffusion is the spreading of particles from an area of high concentration to an area of low concentration. It happens faster in gases than in liquids, and more slowly in solids. Perfume spreading through a room and tea diffusing in hot water are everyday examples.
扩散是粒子从高浓度区域向低浓度区域运动的过程。气体扩散最快，液体次之，固体扩散极慢。香水在房间里散开、茶叶在热水中扩散都是常见的例子。
7. Changes of State | 物态变化
Substances can change from one state to another by heating or cooling. The main state changes are melting (solid to liquid), freezing (liquid to solid), boiling (liquid to gas), condensation (gas to liquid), sublimation (solid directly to gas), and deposition (gas directly to solid).
物质可以通过加热或冷却从一种状态变为另一种状态。主要的物态变化包括：熔化（固态→液态）、凝固（液态→固态）、沸腾（液态→气态）、凝结（气态→液态）、升华（固态直接变为气态）和凝华（气态直接变为固态）。
The temperature at which a substance melts is its melting point, and the temperature at which it boils is its boiling point. Pure substances have sharp melting and boiling points. During a state change, the temperature stays constant even though heating continues, because the energy supplied is used to break particles apart rather than raise temperature.
物质熔化时的温度称为熔点，沸腾时的温度称为沸点。纯净物质具有明确的熔点和沸点。在物态变化过程中，即使继续加热，温度也保持不变，因为供给的能量被用于克服粒子间的吸引力，而不是提高温度。
Evaporation is different from boiling. Evaporation occurs at the surface of a liquid at any temperature, while boiling happens throughout the liquid at its boiling point. Factors like temperature, surface area, and air movement can speed up evaporation.
蒸发不同于沸腾。蒸发在任何温度下发生在液体表面，而沸腾是在沸点时整个液体内部发生的剧烈汽化。温度、表面积和空气流动等因素可以加快蒸发速度。
8. The Solar System | 太阳系
Our Solar System consists of the Sun, eight planets, dwarf planets, moons, asteroids, and comets. The planets in order from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four are rocky planets; the last four are gas giants.
太阳系由太阳、八大行星、矮行星、卫星、小行星和彗星组成。按离太阳从近到远的顺序，八大行星为：水星、金星、地球、火星、木星、土星、天王星和海王星。前四颗是岩石行星，后四颗是气态巨行星。
The Sun is the star at the centre of our Solar System, and it provides the gravitational pull that keeps the planets in orbit. The orbits of the planets are slightly elliptical (oval shaped), not perfect circles. Each planet spins on its own axis, giving it day and night.
太阳是太阳系中心的恒星，它的引力使行星保持在各自的轨道上。行星的轨道是略微椭圆的，并非完美的圆形。每颗行星还绕自己的轴自转，从而产生昼夜交替。
The asteroid belt lies between Mars and Jupiter and contains many rocky objects. Comets are icy bodies that develop glowing tails when they approach the Sun. Moons, or natural satellites, orbit planets; Earth has one moon, while Jupiter has over 70 known moons.
小行星带位于火星和木星之间，包含大量的岩石碎块。彗星是由冰物质组成的天体，靠近太阳时会形成发光的彗尾。卫星（天然卫星）环绕行星运行；地球有一颗卫星，木星已知的卫星超过 70 颗。
9. Gravity and Space | 引力与太空
Gravity is a non-contact force that attracts any two objects with mass towards each other. The greater the mass of an object, the stronger its gravitational pull. On Earth, gravity gives objects weight and causes them to fall towards the ground with an acceleration of about 9.8 m/s² (often rounded to 10 m/s² for calculations).
引力是一种非接触力，将任何两个有质量的物体相互吸引。物体的质量越大，其引力就越强。在地球上，引力使物体具有重量，并使它们以约 9.8 m/s² 的加速度落向地面（计算时常取 10 m/s²）。
Weight and mass are not the same. Mass is the amount of matter in an object, measured in kilograms (kg), and does not change wherever you are. Weight is the force of gravity acting on that mass, measured in newtons (N). The relationship is:
Weight = Mass × Gravitational field strength (W = m × g)
重量和质量是不同的概念。质量是物体所含物质的多少，单位是千克（kg），且在任何地方都不变。重量是作用在该质量上的重力，单位是牛顿（N）。二者关系为：
重量 = 质量 × 引力场强度 (W = m × g)
Orbiting objects, such as the Moon around Earth and Earth around the Sun, are in a constant state of free fall. The balance between forward motion and gravitational pull creates a curved path called an orbit. Satellites are placed into orbit to provide communication, weather data, and global positioning.
绕行的天体，如月球绕地球、地球绕太阳，始终处于自由落体状态。向前的运动与引力之间的平衡形成弯曲的轨道，这就是轨道运动。人造卫星被送入轨道，用于通信、气象观测和全球定位等服务。
10. Practical Skills and Measurements | 实验技能与测量
Good practical skills are essential in physics. You should know how to use common measuring instruments safely and accurately. A ruler or tape measure is used for length, a stopwatch for time, a mass balance for mass, and a thermometer for temperature. Always read the scale at eye level to avoid parallax error.
良好的实验技能在物理中至关重要。你需要学会如何安全、准确地使用常用仪器：直尺或卷尺测量长度，秒表记录时间，天平称量质量，温度计测量温度。每次读数时要平视刻度，避免视差。
example 1 km = 1000 m, 1 hour = 3600 s. In graphs, plot the independent variable on the x‑axis and the dependent variable on the y‑axis, and draw a line of best fit if the points show a trend.
记录数据时，必须写出正确的单位。必要时进行单位换算，例如 1 km = 1000 m，1 小时 = 3600 秒。绘图时，将自变量放在 x 轴，因变量放在 y 轴，若数据点呈现变化趋势则画出最佳拟合线。
Safety rules in the lab include wearing eye protection when required, tying back long hair, and never eating or drinking. Understand the difference between a hazard (something that can cause harm) and a risk (the chance of being harmed). Always follow your teacher’s instructions.
实验室安全规则包括：必要时佩戴护目镜，束起长发，不饮食。要理解危害（可能造成伤害的事物）和风险（受到伤害的可能性）之间的区别。始终听从老师的指导。
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