📚 Core Topics Checklist for Year 9 CIE Science | Year 9 CIE 科学核心知识点梳理
This article provides a bilingual overview of the essential topics in the Year 9 CIE Science curriculum, covering Physics, Chemistry and Biology. Use it as a revision checklist or study guide to ensure you have a solid grounding before moving on to IGCSE.
本文为 Year 9 CIE 科学课程的核心内容提供中英双语梳理，涵盖物理、化学和生物三科。可将其作为复习清单或学习指南，确保在升入 IGCSE 之前打下扎实基础。
1. Forces and Motion | 力与运动
A force is a push or a pull that can change an object’s speed, direction or shape. Forces are measured in newtons (N). Common types include gravity, friction, air resistance and tension. The relationship between force (F), mass (m) and acceleration (a) is given by Newton’s second law:
F = m × a
力是推或拉，可以改变物体的速度、方向或形状。力的单位是牛顿（N）。常见的力包括重力、摩擦力、空气阻力和拉力。力（F）、质量（m）与加速度（a）之间的关系由牛顿第二定律描述：F = m × a。
Speed is the distance travelled per unit time; velocity is speed in a given direction. You can represent motion using distance–time and speed–time graphs. The gradient of a distance–time graph gives speed, while the gradient of a speed–time graph gives acceleration.
speed = distance ÷ time
速率是单位时间内移动的距离；速度是具有方向的速率。可以用距离–时间图和速度–时间图表示运动。距离–时间图的斜率表示速率，速度–时间图的斜率表示加速度。
2. Energy Transfers and Efficiency | 能量传递与效率
Energy can be stored in different forms: kinetic, gravitational potential, thermal, chemical, elastic, nuclear and electromagnetic. Energy is transferred between stores by heating, working (mechanical transfer), or by waves (radiation). The law of conservation of energy states that energy cannot be created or destroyed, only transferred or converted.
能量可以以不同形式储存：动能、重力势能、热能、化学能、弹性势能、核能和电磁能。能量通过加热、做功（机械传递）或波（辐射）在储存库之间传递。能量守恒定律指出，能量既不能被创造也不能被消灭，只能被传递或转化。
Efficiency is the ratio of useful output energy to total input energy, expressed as a percentage. In any transfer, some energy is always dissipated as thermal energy, reducing efficiency.
Efficiency = (useful output ÷ total input) × 100%
效率是有用输出能量与总输入能量之比，以百分比表示。在任何传递过程中，总有一部分能量以热能形式散失，从而降低效率。
3. Waves and Light | 波与光
Waves transfer energy without transferring matter. Transverse waves (e.g., light, water ripples) oscillate perpendicular to the direction of energy travel; longitudinal waves (e.g., sound) oscillate parallel to the direction. Key wave properties include wavelength (λ), frequency (f), amplitude and wave speed (v). The wave speed equation is:
v = f × λ
波传递能量而不传递物质。横波（如光、水波）的振动方向与能量传播方向垂直；纵波（如声音）的振动方向平行于传播方向。波的关键属性包括波长 (λ)、频率 (f)、振幅和波速 (v)。波速方程为：v = f × λ。
Light travels in straight lines and can be reflected and refracted. The law of reflection states that the angle of incidence (i) equals the angle of reflection (r). Refraction occurs because light changes speed when it passes from one medium to another. White light can be dispersed by a prism into a spectrum of colours (red, orange, yellow, green, blue, indigo, violet).
光沿直线传播，可以发生反射和折射。反射定律指出，入射角 (i) 等于反射角 (r)。折射是因为光从一种介质进入另一种介质时速度改变。白光可被棱镜色散成七色光谱（红、橙、黄、绿、蓝、靛、紫）。
4. Electrical Circuits | 电路
An electric circuit needs a complete loop for current to flow. Current (I) is the rate of flow of charge, measured in amperes (A). Voltage (V) is the energy transferred per unit charge, measured in volts (V). Resistance (R) opposes the current and is measured in ohms (Ω). Ohm’s law links these quantities:
V = I × R
电路需要完整的回路才能使电流流动。电流 (I) 是电荷流动的速率，单位为安培 (A)。电压 (V) 是每单位电荷传递的能量，单位为伏特 (V)。电阻 (R) 阻碍电流，单位为欧姆 (Ω)。欧姆定律将三者联系起来：V = I × R。
Components can be arranged in series (a single path) or in parallel (multiple branches). In a series circuit, the current is the same everywhere and the voltage is shared. In a parallel circuit, the voltage across each branch is the same, while the current splits between branches.
电路元件可以串联（单一路径）或并联（多条支路）。串联电路中各处电流相等，电压分摊；并联电路中各支路电压相同，电流分流。
5. States of Matter and Particulate Nature | 物质状态与粒子性质
Matter exists as solid, liquid or gas. According to the particle model: solids have particles closely packed in a regular pattern, vibrating in fixed positions; liquids have particles close together but able to move past each other; gases have widely spaced particles moving rapidly and randomly. Changes of state (melting, boiling, condensing, freezing, sublimation) involve energy transfers without a change in temperature during the process.
物质以固态、液态或气态存在。根据粒子模型：固体粒子紧密排列并呈规则分布，在固定位置振动；液体粒子紧挨但可相互滑动；气体粒子间距大，快速且随机地运动。状态变化（熔化、沸腾、凝结、凝固、升华）涉及能量传递，但在变化过程中温度保持不变。
Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration. It occurs in liquids and gases and provides evidence for the particle model.
扩散是粒子从高浓度区域向低浓度区域运动的过程，发生在液体和气体中，为粒子模型提供了证据。
6. Atomic Structure and the Periodic Table | 原子结构与元素周期表
All substances are made of atoms. An atom consists of a nucleus containing protons (positive) and neutrons (neutral), with electrons (negative) orbiting in shells. The atomic number is the number of protons; the mass number is the total number of protons + neutrons. Isotopes are atoms of the same element with different numbers of neutrons.
所有物质都由原子构成。原子由包含质子（正电）和中子（中性）的原子核，以及围绕核运动的带负电的电子组成。原子序数是质子数；质量数是质子数 + 中子数。同位素是质子数相同但中子数不同的同种元素的原子。
The periodic table arranges elements in order of increasing atomic number. Vertical columns are called groups; elements in the same group have similar chemical properties because they have the same number of outer-shell electrons. Horizontal rows are periods, which correspond to the number of electron shells.
元素周期表按原子序数递增排列。竖列称为族；同一族的元素化学性质相似，因为它们的最外层电子数相同。横行称为周期，对应电子层数。
7. Chemical Reactions and Equations | 化学反应与方程式
In a chemical reaction, atoms are rearranged to form new substances. Reactants are the starting substances, and products are the substances formed. The law of conservation of mass states that the total mass of reactants equals the total mass of products. Balanced symbol equations show the same number of atoms of each element on both sides.
化学反应中原子重新排列，形成新物质。反应物是起始物质，生成物是形成的新物质。质量守恒定律指出，反应物的总质量等于生成物的总质量。配平的符号方程式两边每种元素的原子数目相等。
Common reaction types include combustion (reaction with oxygen, releasing heat), neutralisation (acid + base → salt + water) and displacement (a more reactive element displaces a less reactive one from a compound). The reactivity series helps predict whether a displacement reaction will occur.
常见的反应类型包括燃烧（与氧气反应，释放
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