📚 KS3 Edexcel Physics: Key Knowledge Points | KS3 Edexcel 物理：核心知识点梳理
Physics at Key Stage 3 builds the foundations for understanding energy, forces, waves, electricity, and the material world. This revision guide summarises the core knowledge points specified by the Edexcel KS3 curriculum, helping you to form a clear big picture and master essential ideas.
KS3 阶段的物理为理解能量、力、波、电学和物质世界打下基础。本复习指南梳理了 Edexcel KS3 课程指定的核心知识点，帮助你形成清晰的全貌并掌握基本概念。
1. Energy Stores and Transfers | 能量储存与转移
Energy is the capacity to do work and is measured in joules (J). There are eight main stores: kinetic, gravitational potential, chemical, elastic potential, thermal (internal), nuclear, magnetic and electrostatic.
能量是做功的能力，单位是焦耳 (J)。共有八种主要储存形式：动能、重力势能、化学能、弹性势能、热能（内能）、核能、磁能和静电能量。
A system is an object or group of objects under study. When a system changes, energy is transferred between stores.
系统是指所研究的单个物体或物体组。系统发生变化时，能量在储存库之间转移。
Energy can be transferred mechanically (by a force doing work), electrically (when a current flows), by heating or by radiation (e.g. light or sound waves).
能量可以通过机械方式（力做功）、电学方式（电流流动）、加热或辐射（如光波或声波）传递。
Energy is conserved: it cannot be created or destroyed, only transferred from one store to another.
能量是守恒的：它既不能被创造也不能被消灭，只能从一种储存形式转移到另一种。
2. Energy Resources | 能源
Energy resources are used to generate electricity or provide heat. They are classified as renewable or non-renewable.
能源用于发电或供热。它们分为可再生能源和不可再生能源。
Non-renewable resources include fossil fuels (coal, oil, natural gas) and nuclear fuel. They are finite and will run out; burning fossil fuels releases carbon dioxide and other pollutants.
不可再生能源包括化石燃料（煤、石油、天然气）和核燃料。它们储量有限，终将耗尽；燃烧化石燃料会释放二氧化碳和其他污染物。
Renewable resources include solar, wind, tidal, wave, hydroelectric, geothermal and biomass. They are replenished naturally and produce little or no greenhouse gases during operation.
可再生能源包括太阳能、风能、潮汐能、波浪能、水力发电、地热能和生物质能。它们能自然补充，运行中排放极少或不排放温室气体。
The choice of energy resource depends on factors such as cost, reliability, environmental impact and the local availability of wind, sun or water.
能源的选择取决于成本、可靠性、环境影响以及当地风、阳光或水资源的可用性等因素。
3. Forces and Motion | 力与运动
A force is a push or a pull that can change an object’s shape, speed or direction. Force is measured in newtons (N).
力是推或拉，可以改变物体的形状、速度或方向。力的单位是牛顿 (N)。
Contact forces (e.g. friction, air resistance, tension) act when objects touch. Non-contact forces (gravity, magnetism, electrostatic force) act over a distance.
接触力（如摩擦力、空气阻力、拉力）在物体接触时产生。非接触力（重力、磁力、静电力）隔空作用。
The weight of an object is the force of gravity acting on its mass: weight (N) = mass (kg) × gravitational field strength (N/kg). On Earth, g ≈ 10 N/kg.
物体的重量是作用于其质量上的重力：重量 (N) = 质量 (kg) × 重力场强度 (N/kg)。在地球上，g ≈ 10 N/kg。
Balanced forces produce no change in motion; the object remains at rest or moves at a steady speed. Unbalanced forces cause acceleration, deceleration or a change in direction.
平衡力不改变运动状态；物体保持静止或匀速运动。非平衡力导致加速、减速或方向改变。
Average speed can be calculated using:
平均速度可用以下公式计算：
average speed = total distance ÷ total time
平均速度 = 总路程 ÷ 总时间
Distance–time graphs show how far an object has moved over time; a straight, sloping line indicates constant speed, and a horizontal line means the object is stationary.
距离–时间图像显示物体的位移随时间的变化；一条倾斜的直线表示匀速运动，水平线表示物体静止。
4. Electricity and Circuits | 电与电路
Electric current is the flow of electric charge. In a metal wire, current is a flow of negatively charged electrons.
电流是电荷的流动。在金属导线中，电流是带负电的电子的流动。
Current is measured in amperes (A) using an ammeter connected in series. Potential difference (voltage) is measured in volts (V) using a voltmeter connected in parallel.
电流用串联的电流表测量，单位为安培 (A)。电位差（电压）用并联的电压表测量，单位为伏特 (V)。
Resistance is a measure of how difficult it is for current to flow; the unit is the ohm (Ω).
电阻衡量电流流动的难易程度，单位是欧姆 (Ω)。
A simple series circuit has all components connected one after the other along a single loop. If one component breaks, the circuit is broken and current stops everywhere.
简单的串联电路将所有元件首尾相连在单一回路中。若一个元件损坏，电路断开，各处电流均停止。
In a parallel circuit components are connected on separate branches; the current splits and the potential difference across each branch is the same as the supply voltage. This is the standard wiring method in homes.
在并联电路中，元件连接在独立分支上；电流分流，各支路两端电位差与电源电压相等。这是家庭电路的标准布线方式。
Conductors allow charge to flow easily (e.g. copper). Insulators do not (e.g. rubber).
导体允许电荷轻易通过（如铜），绝缘体则不能（如橡胶）。
5. Magnetism and Electromagnetism | 磁与电磁
A magnet has a north pole and a south pole. Like poles repel each other; unlike poles attract.
磁铁有北极和南极。同极相互排斥，异极相互吸引。
Magnetic materials such as iron, nickel and cobalt are attracted to magnets. The region around a magnet where a magnetic force is felt is called the magnetic field, drawn as lines from north to south.
磁性材料（如铁、镍、钴）会被磁铁吸引。磁铁周围能感受到磁力的区域叫做磁场，用从北极指向南极的线表示。
An electromagnet is a solenoid (coil of wire) with an iron core. When a current flows, it creates a strong magnetic field that can be switched on and off.
电磁铁是一个带有铁芯的螺线管（线圈）。通电时产生强磁场，且可以随时通断。
The strength of an electromagnet can be increased by raising the current, adding more turns to the coil or using a soft iron core.
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性。
Electromagnets are used in cranes for lifting scrap metal, in electric bells, relays and loudspeakers.
电磁铁用于起重机抓取废铁、电铃、继电器和扬声器中。
6. Waves: Sound | 波：声音
Sound is produced by vibrating objects. These vibrations travel through a medium (solid, liquid or gas) as a longitudinal wave.
声音由物体振动产生。这些振动以纵波的形式通过介质（固体、液体或气体）传播。
In a longitudinal wave, particles vibrate back and forth parallel to the direction of energy transfer; compressions are regions of high pressure, and rarefactions are regions of low pressure.
在纵波中，粒子沿着能量传递方向来回振动；压缩区是高压区域，稀疏区是低压区域。
Sound cannot travel through a vacuum because there are no particles to transfer the vibrations.
声音无法在真空中传播，因为没有粒子可以传递振动。
The speed of sound varies in different media: fastest in solids, slower in liquids, and slowest in gases.
声音在不同介质中的速度不同：固体中最快，液体中较慢，气体中最慢。
Pitch is determined by the frequency of the sound wave (higher frequency → higher pitch). Loudness depends on the amplitude of the wave.
音调由声波的频率决定（频率越高，音调越高）。响度取决于波的振幅。
The normal human hearing range is approximately 20 Hz to 20 000 Hz. Ultrasound is sound above this range, used for medical imaging and cleaning.
人类正常听觉范围约为 20 Hz 至 20 000 Hz。超声波是超出此范围的声音，用于医学成像和清洁。
7. Waves: Light | 波：光
Light travels in straight lines as a transverse wave at a speed of 300 000 000 m/s in a vacuum.
光以横波形式直线传播，在真空中速度约为 3 × 10⁸ m/s。
When light strikes a smooth shiny surface, it is reflected obeying the law of reflection: angle of incidence = angle of reflection. These angles are measured from the normal, an imaginary line perpendicular to the surface.
光照射到光滑镜面时发生反射，遵循反射定律：入射角 = 反射角。这些角度都从法线（垂直于表面的假想线）开始测量。
Refraction is the change in direction of light when it passes from one transparent medium to another with a different density. Light bends towards the normal when entering a denser medium.
折射是光从一种透明介质进入密度不同的另一种介质时方向发生改变的现象。光进入较密介质时向法线方向偏折。
White light can be dispersed into a spectrum of colours (red, orange, yellow, green, blue, indigo, violet) when it passes through a prism. This happens because different colours of light travel at different speeds in glass and therefore bend by different amounts.
白光通过棱镜时可以色散为光谱（红、橙、黄、绿、蓝、靛、紫）。这是因为不同颜色的光在玻璃中传播速度不同，因而偏折的角度不同。
Colour filters work by transmitting certain colours and absorbing others. A red apple appears red because it reflects red light and absorbs other colours.
颜色滤光片通过透射某些颜色并吸收其他颜色来工作。红苹果呈现红色是因为它反射红光并吸收其他颜色。
8. The Particle Model of Matter | 物质的粒子模型
All matter is made of tiny particles (atoms or molecules) that are constantly moving. The arrangement and motion of these particles explain the properties of solids, liquids and gases.
所有物质都由不断运动的微小粒子（原子或分子）构成。这些粒子的排列和运动方式解释了固体、液体和气体的性质。
In solids, particles are tightly packed in a regular pattern and vibrate in fixed positions. Solids have a definite shape and volume.
固体中粒子紧密排列成规则图案，在固定位置振动。固体有确定的形状和体积。
In liquids, particles are close together but can slide past each other. Liquids have a fixed volume but take the shape of their container.
液体中粒子相距较近，但可以相互滑动。液体有固定的体积但取盛装容器的形状。
In gases, particles are far apart and move quickly in all directions. Gases have no fixed shape or volume and can be compressed easily.
气体中粒子相距很远，向各个方向快速运动。气体没有固定的形状或体积，容易被压缩。
Heating increases the kinetic energy of particles, causing them to move faster and, at certain temperatures, to overcome forces between them, leading to changes of state: melting, boiling, freezing, condensing and sublimation.
加热使粒子的动能增加，运动加快，并在特定温度下克服粒子间作用力，导致物态变化：熔化、沸腾、凝固、冷凝和升华。
Mass is conserved during changes of state because the number and type of particles remain the same.
物态变化中质量守恒，因为粒子的数量和种类不变。
9. Atoms, Elements and Compounds | 原子、元素和化合物
An element is a substance made of only one type of atom. There are about 100 elements, listed in the Periodic Table.
元素是只由一种原子组成的物质。大约有 100 种元素，排列在元素周期表中。
Atoms contain a tiny central nucleus (protons and neutrons) surrounded by electrons orbiting in shells. Protons have a positive charge, electrons are negative, and neutrons have no charge.
原子包含微小的原子核（质子和中子），周围有电子在壳层中绕核运动。质子带正电荷，电子带负电荷，中子不带电。
Atomic number is the number of protons in an atom, which identifies the element. Mass number is the total number of protons plus neutrons.
原子序数是原子中的质子数，它决定了元素的种类。质量数是质子数加中子数的总和。
A compound is a substance formed when two or more different elements are chemically bonded together. The properties of a compound are different from the elements it is made from, such as water (H₂O) from hydrogen and oxygen.
化合物是两种或更多种不同元素通过化学键结合形成的物质。化合物的性质不同于组成它的元素，例如水 (H₂O) 由氢和氧组成。
Simple chemical reactions can be represented by word equations or symbol equations that must be balanced, as atoms are rearranged and conserved in a reaction.
简单的化学反应可以用文字方程式或符号方程式表示，且必须配平，因为反应中原子重新排列且数目守恒。
For example, the combustion of methane can be written as:
例如，甲烷的燃烧可表示为：
CH₄ + 2O₂ → CO₂ + 2H₂O
10. Earth and Space | 地球与太空
The Earth rotates on its axis once every 24 hours, causing day and night. Its axis is tilted, which, combined with its orbit around the Sun, creates seasons.
地球每 24 小时自转一周，产生昼夜。地轴倾斜，加上绕日公转，形成四季。
The Solar System consists of the Sun (a star), eight planets with their moons, dwarf planets, asteroids and comets. Gravity holds the system together.
太阳系由太阳（一颗恒星）、八大行星及其卫星、矮行星、小行星和彗星组成。万有引力将整个系统维系在一起。
The force of gravity provides the centripetal force that keeps planets and moons in nearly circular orbits. The closer a planet is to the Sun, the greater the gravitational pull and the shorter its orbital period.
万有引力提供了使行星和卫星保持近圆轨道所需的向心力。行星离太阳越近，引力越强，公转周期越短。
We see the Moon because it reflects sunlight. The Moon’s phases (new, crescent, quarter, gibbous, full) depend on the relative positions of the Earth, Moon and Sun.
我们看见月亮是因为它反射太阳光。月相（新月、蛾眉月、弦月、凸月、满月）取决于地球、月球和太阳的相对位置。
A solar eclipse happens when the Moon comes between the Sun and Earth, casting a shadow on the Earth. A lunar eclipse occurs when the Earth lies between the Sun and the Moon.
当月球运行至日地之间时发生日食，在地球上投下阴影。当地球处于日月之间时发生月食。
11. Scientific Enquiry Skills | 科学探究技能
Good experimental design involves identifying independent, dependent and control variables. The independent variable is the one you change, the dependent variable is the one you measure, and control variables are kept the same to ensure a fair test.
良好的实验设计需要明确自变量、因变量和控制变量。自变量是操作改变的量，因变量是测量的结果，控制变量则保持不变以保证公平测试。
Measurements should be repeated and averaged to improve reliability. Anomalous results that do not fit the pattern should be identified and possibly excluded.
测量应重复进行并取平均值以提高可靠性。应识别并可能剔除不符合规律的异常结果。
Data can be presented in tables, bar charts, line graphs or scatter plots. In a line graph, the independent variable usually goes on the x-axis and the dependent variable on the y-axis.
数据可用表格、条形图、线图或散点图展示。线图中自变量通常置于 x 轴，因变量置于 y 轴。
A conclusion should describe the relationship found and refer to the data. A prediction that is supported by evidence may become a scientific theory.
结论应描述发现的规律并引用数据。被证据支持的预测可能成为科学理论。
Hazards and risks in experiments must be assessed. Always follow safety rules, wear eye protection when necessary, and handle electrical equipment and heat sources carefully.
实验中必须评估危害与风险。始终遵守安全规则，必要时佩戴护目镜，谨慎操作电气设备和热源。
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