📚 Year 9 CAIE Science Core Knowledge Review | Year 9 CAIE 科学核心知识点梳理
The Cambridge Lower Secondary Science curriculum for Year 9 (Stage 9) builds a strong foundation in biology, chemistry and physics. Mastering these core concepts is essential for success in the Checkpoint assessment and for a smooth transition to IGCSE. This article presents a clear, bilingual summary of the key knowledge areas you need to know.
剑桥初中科学 Year 9（第 9 阶段）课程为生物、化学和物理打下坚实基础。掌握这些核心概念对于在 Checkpoint 考试中取得成功、平稳过渡到 IGCSE 至关重要。本文以清晰的双语总结了你需要掌握的关键知识领域。
1. Cells and Organisation | 细胞与组织
All living organisms are made up of cells. Cells are the basic structural and functional units of life.
所有生物体都由细胞构成。细胞是生命的基本结构和功能单位。
Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria. The nucleus controls the cell’s activities and carries genetic material.
动物细胞含有细胞核、细胞质、细胞膜和线粒体。细胞核控制细胞的活动并携带遗传物质。
Plant cells have additional structures: a rigid cell wall made of cellulose, chloroplasts for photosynthesis, and a large permanent vacuole containing cell sap.
植物细胞有额外的结构：由纤维素构成的坚硬细胞壁、进行光合作用的叶绿体，以及含有细胞液的大液泡。
Groups of similar cells form tissues, tissues work together to form organs, and organs are organised into organ systems, such as the digestive system.
一群相似的细胞形成组织，组织共同工作形成器官，器官组成器官系统，例如消化系统。
2. Life Processes and Human Systems | 生命过程与人体系统
All living things carry out seven life processes, often remembered by the acronym MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition.
所有生物都进行七种生命过程，通常用首字母缩写 MRS GREN 来记忆：运动、呼吸、感觉、生长、繁殖、排泄和营养。
The human digestive system breaks down large, insoluble food molecules into small, soluble ones that can be absorbed into the blood.
人体消化系统将大的、不溶于水的食物分子分解成可溶于水的小分子，以便被吸收进血液。
The circulatory system consists of the heart, blood vessels and blood. It transports oxygen, nutrients, hormones and waste products around the body.
循环系统由心脏、血管和血液组成。它将氧气、营养物质、激素和废物运送到全身各处。
dioxide and water as waste products: glucose + oxygen → carbon dioxide + water (+ energy).
有氧呼吸发生在线粒体中，利用氧气从葡萄糖中释放能量，产生二氧化碳和水作为废物：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。
During gas exchange in the lungs, oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses in the opposite direction to be exhaled.
在肺部气体交换过程中，氧气从肺泡扩散进血液，同时二氧化碳反向扩散被呼出体外。
3. Reproduction and Genetics | 繁殖与遗传
Sexual reproduction involves the fusion of male and female gametes (sperm and egg) to form a zygote. Offspring show variation because they inherit a mix of genetic information from both parents.
有性繁殖涉及雄配子和雌配子（精子和卵子）的结合形成受精卵。后代表现出变异，因为它们继承了两个亲本的混合遗传信息。
The nucleus of a cell contains chromosomes made of DNA. A gene is a small section of DNA that codes for a particular protein or characteristic.
细胞核含有由 DNA 组成的染色体。基因是 DNA 上的一个小片段，编码特定的蛋白质或性状。
In humans, sex is determined by the X and Y chromosomes. Females have XX and males have XY.
在人类中，性别由 X 和 Y 染色体决定。女性为 XX，男性为 XY。
Asexual reproduction produces genetically identical offspring (clones) from a single parent. Examples include binary fission in bacteria and runners in strawberry plants.
无性繁殖从一个亲本产生遗传上完全相同的后代（克隆）。例子包括细菌的二分裂和草莓植物的匍匐茎。
Basic Mendelian genetics can be represented using Punnett squares to predict the probability of inheriting dominant and recessive alleles for a trait.
可以用旁氏表（Punnett squares）展示基本的孟德尔遗传规律，以预测性状的显性和隐性等位基因的遗传概率。
4. States of Matter and Particle Theory | 物质状态与粒子理论
Matter exists in three main states: solid, liquid and gas. The particle theory explains that all substances are made of tiny particles that are constantly moving.
物质存在三种主要状态：固体、液体和气体。粒子理论解释，所有物质都由不断运动的微小粒子组成。
In solids, particles are held together in a fixed, regular arrangement and can only vibrate. Solids have a fixed shape and volume.
在固体中，粒子结合在一起，拥有固定的规则排列，只能振动。固体具有固定的形状和体积。
In liquids, particles are close together but can move past one another, so liquids flow and take the shape of their container while keeping a fixed volume.
在液体中，粒子彼此靠近但可以相对滑动，因此液体会流动，并呈现容器的形状，同时保持固定体积。
In gases, particles are far apart, move rapidly in all directions and have no fixed shape or volume. Gases can be compressed easily.
在气体中，粒子相距很远，快速向各个方向运动，没有固定的形状或体积。气体很容易被压缩。
Changes of state, such as melting, boiling, condensation and freezing, are physical changes. The particles themselves stay the same, but their arrangement and energy change.
状态变化，如熔化、沸腾、冷凝和凝固，是物理变化。粒子本身不变，但排列方式和能量发生变化。
5. Atoms, Elements and Compounds | 原子、元素与化合物
An element is a substance made of only one type of atom. A compound contains atoms of two or more different elements chemically bonded together.
元素是由同一种原子组成的物质。化合物含有两种或更多种不同元素的原子，通过化学键结合在一起。
Atoms consist of a central nucleus containing protons and neutrons, with electrons moving around the nucleus in shells.
原子由一个包含质子和中子的中央原子核，以及在其周围壳层中运动的电子构成。
The atomic number of an element is the number of protons in its nucleus, and the mass number is the total number of protons plus neutrons.
元素的原子序数是其原子核中的质子数，质量数是质子数与中子数之和。
Electrons are arranged in shells with capacities of 2, 8, 8 for the first three shells. The electronic configuration of oxygen (atomic number 8) is 2.6.
电子排列在壳层中，前三个壳层最多容纳 2、8、8 个电子。氧（原子序数 8）的电子排布是 2.6。
The periodic table arranges elements in order of increasing atomic number. Groups contain elements with similar chemical properties because they have the same number of electrons in their outer shell.
元素周期表按原子序数递增排列。族中的元素化学性质相似，因为它们最外层电子数相同。
6. Chemical Reactions | 化学反应
In a chemical reaction, atoms are rearranged to form new substances. No atoms are created or destroyed; this is the law of conservation of mass.
在化学反应中，原子重新排列形成新物质。原子不会被创造或消灭；这就是质量守恒定律。
m + oxygen → magnesium oxide. Symbol equations use chemical formulae and must be balanced.
文字表达式表示反应物和生成物，例如：镁 + 氧气 → 氧化镁。符号方程式使用化学式并且必须配平。
n (breaking down a substance using heat), and neutralisation (acid + base → salt + water).
常见的反应类型包括燃烧（在氧气中燃烧）、热分解（用热分解物质）和中和反应（酸 + 碱 → 盐 + 水）。
less reactive metal from its compound, e.g. zinc + copper sulfate → zinc sulfate + copper.
在置换反应中，较活泼的金属将较不活泼的金属从其化合物中置换出来，例如：锌 + 硫酸铜 → 硫酸锌 + 铜。
A catalyst is a substance that speeds up a reaction without being used up. Enzymes are biological catalysts that work in living organisms.
催化剂是一种加快反应速度而自身不被消耗的物质。酶是活体中的生物催化剂。
7. Forces and Motion | 力与运动
A force is a push or a pull that can change the speed, direction or shape of an object. Forces are measured in newtons (N).
力是一种推或拉，可以改变物体的速度、方向或形状。力的单位是牛顿（N）。
If forces on an object are balanced, the object remains stationary or continues to move at a constant speed. Unbalanced forces cause a change in speed or direction (acceleration).
如果物体受到的力是平衡的，物体将保持静止或继续以恒定速度运动。不平衡的力会导致速度或方向改变（加速）。
The relationship between distance, time and speed is central:
average speed = distance ÷ time
距离、时间和速度之间的关系是核心的：
平均速度 = 距离 ÷ 时间
Gravity is a non-contact force that pulls objects towards the centre of the Earth. Weight is the force of gravity on an object and is calculated using:
weight = mass × gravitational field strength (W = m × g)
重力是一种非接触力，将物体拉向地心。重量是作用在物体上的重力，计算公式为：
重量 = 质量 × 重力场强度 (W = m × g)
Friction opposes motion between two surfaces that are in contact and often produces heat.
摩擦力阻碍接触的两个表面之间的运动，常会产生热量。
8. Energy Forms and Transfers | 能量形式与转换
Energy exists in many forms, including kinetic (movement), gravitational potential, elastic potential, thermal (heat), chemical, electrical, light and sound energy.
能量有多种形式，包括动能（运动）、重力势能、弹性势能、热能、化学能、电能、光能和声能。
The law of conservation of energy states that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.
能量守恒定律指出，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。
Gravitational potential energy depends on mass, height and gravitational field strength:
GPE = m × g × h
重力势能取决于质量、高度和重力场强度：
GPE = m × g × h
Kinetic energy depends on mass and speed:
KE = ½ × m × v²
动能取决于质量和速度：
KE = ½ × m × v²
Efficiency measures how much of the input energy is transferred into useful output energy:
efficiency = (useful energy output ÷ total energy input) × 100%
效率衡量有多少输入能量转化为有用的输出能量：
效率 = (有用能量输出 ÷ 总能量输入) × 100%
9. Electricity and Magnetism | 电与磁
An electric circuit needs a complete loop, a source of energy (cell or battery) and a load (such as a bulb or motor). Current is the flow of electric charge, measured in amperes (A).
电路需要一个完整的回路、一个能量源（电池）和一个负载（如灯泡或电动机）。电流是电荷的流动，单位是安培（A）。
Voltage (potential difference) is the force that pushes the current around the circuit, measured in volts (V). Resistance opposes the current, measured in ohms (Ω).
电压（电势差）是推动电流在电路中流动的力，单位是伏特（V）。电阻阻碍电流，单位是欧姆（Ω）。
Ohm's law links these three quantities:
voltage = current × resistance (V = I × R)
欧姆定律将三者联系起来：
电压 = 电流 × 电阻 (V = I × R)
In a series circuit, the current is the same everywhere and the total resistance is the sum of the individual resistances. In a parallel circuit, the voltage is the same across each branch.
串联电路中，各处电流相等，总电阻是各个电阻之和。并联电路中，各支路两端的电压相同。
An electromagnet is made by passing an electric current through a coil of wire wrapped around a magnetic material such as iron. Its magnetism can be switched on and off.
电磁铁是通过让电流通过缠绕在铁等磁性材料上的线圈制成的。它的磁性可以打开和关闭。
10. Waves: Light and Sound | 波：光与声
Waves transfer energy from one place to another without transferring matter. The key properties of a wave are amplitude, wavelength, frequency and speed.
波将能量从一个地方传递到另一个地方而不传递物质。波的关键特性是振幅、波长、频率和波速。
The wave speed equation is:
wave speed = frequency × wavelength (v = f × λ)
波速公式为：
波速 = 频率 × 波长 (v = f × λ)
Light travels in straight lines and can be reflected and refracted. The law of reflection states that the angle of incidence equals the angle of reflection.
光沿直线传播，可以被反射和折射。反射定律指出，入射角等于反射角。
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 refract by different amounts.
白光通过棱镜时可以被色散成一串彩色光谱（红、橙、黄、绿、蓝、靛、紫）。这是因为不同颜色的光折射程度不同。
Sound is produced by vibrating objects and travels as longitudinal waves through a medium. It cannot travel through a vacuum. Pitch is related to frequency and loudness to amplitude.
声音由振动的物体产生，以纵波的形式通过介质传播。它不能在真空中传播。音调与频率有关，响度与振幅有关。
11. Scientific Enquiry and Experimental Skills | 科学探究与实验技能
In a fair test experiment, you should change only the independent variable, measure the dependent variable, and keep all other variables controlled (constant).
在公平测试实验中，你只能改变自变量，测量因变量，并保持所有其他变量受控（不变）。
A hypothesis is a testable prediction based on scientific knowledge, usually written in an 'If… then…' format.
假设是基于科学知识的一个可检验的预测，通常以“如果……那么……”的形式写出。
Recording data carefully in tables and plotting line graphs or bar charts help identify patterns. The independent variable is plotted on the x-axis and the dependent variable on the y-axis.
仔细地在表格中记录数据，并绘制折线图或条形图有助于识别规律。自变量画在 x 轴上，因变量画在 y 轴上。
When drawing conclusions, refer back to the original hypothesis and discuss whether the evidence supports or refutes it. Evaluate the reliability by looking at repeats and anomalies.
在得出结论时，要回顾最初的假设并讨论证据是支持还是否定它。通过观察重复实验和异常值来评价数据的可靠性。
Always follow safety rules in the laboratory: wear safety goggles, tie back long hair, and handle chemicals, heat sources and electrical equipment with care.
始终遵守实验室安全规则：佩戴护目镜，扎起长发，小心操作化学品、热源和电气设备。
Published by TutorHao | Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图