📚 Year 9 SQA Science: Core Concepts Revision | Year 9 SQA 科学：核心知识点梳理
Welcome to your Year 9 SQA Science revision guide. This article brings together the essential core concepts from biology, chemistry, and physics that you need to master ahead of your assessments. Understanding these fundamentals will build a solid foundation for your National 4 and National 5 qualifications, helping you explain everyday phenomena and design simple experiments with confidence.
欢迎阅读 Year 9 SQA 科学复习指南。本文汇总了生物学、化学和物理学中的核心必知概念，帮助你在评估前牢固掌握。理解这些基础知识将为你未来的 National 4 和 National 5 资格奠定坚实基础，让你能够自信地解释日常现象并设计简单实验。
1. Cells – The Building Blocks of Life | 细胞——生命的基石
All living organisms are composed of cells. Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria, while plant cells have the additional features of a rigid cell wall, a large central vacuole and chloroplasts that carry out photosynthesis. The nucleus controls cell functions by housing the genetic material (DNA). Specialised cells, such as red blood cells or root hair cells, have adaptations that allow them to perform specific roles efficiently.
所有生物体都由细胞组成。动物细胞含有细胞核、细胞质、细胞膜和线粒体，而植物细胞还具有坚硬的细胞壁、大型中央液泡以及进行光合作用的叶绿体。细胞核通过储存遗传物质（DNA）来控制细胞功能。特化细胞（如红细胞或根毛细胞）具有适应结构，能够高效地执行特定功能。
| Organelle / 细胞器 | Function / 功能 |
|---|---|
| Nucleus / 细胞核 | Contains DNA and controls cell activities (包含DNA，控制细胞活动) |
| Mitochondria / 线粒体 | Site of aerobic respiration, releasing energy (有氧呼吸场所，释放能量) |
| Chloroplasts / 叶绿体 | Absorb light energy for photosynthesis (吸收光能进行光合作用) – plant cells only |
| Cell wall / 细胞壁 | Provides structural support (提供结构支撑) – plant cells |
2. Atoms, Elements, and Compounds | 原子、元素与化合物
All substances are made from tiny particles called atoms. An element is a pure substance containing only one type of atom, while a compound consists of two or more different elements chemically bonded in fixed proportions. For example, water (H₂O) is a compound made from hydrogen and oxygen atoms. Chemical formulas show the types and numbers of atoms in a substance; the subscript number indicates how many atoms of that element are present.
所有物质都由称为原子的微小粒子组成。元素是只含一种原子的纯净物质，而化合物由两种或多种不同元素以固定比例通过化学键结合而成。例如，水（H₂O）是由氢原子和氧原子组成的化合物。化学式表示物质中原子的种类和数目；右下角的数字表示该元素的原子数量。
Atoms have a small central nucleus containing protons and neutrons, surrounded by electrons in shells. The number of protons (atomic number) determines the element. Neutral atoms have equal numbers of protons and electrons. Ions form when atoms gain or lose electrons, producing charged particles such as Na⁺ or Cl⁻.
原子有一个小的中心原子核，包含质子和中子，核外电子排布在电子层中。质子数（原子序数）决定了元素的种类。中性原子的质子数和电子数相等。当原子得到或失去电子时形成离子，产生带电粒子，如 Na⁺ 或 Cl⁻。
3. The Periodic Table and Chemical Patterns | 元素周期表与化学规律
The periodic table arranges elements in order of increasing atomic number and groups them by similar chemical properties. Vertical columns are called groups; elements in the same group have the same number of electrons in their outer shell, which explains their similar reactivity. For example, Group 1 metals (alkali metals) are all highly reactive and form 1+ ions, while Group 7 elements (halogens) are reactive non‑metals that form 1− ions. The horizontal rows are periods, and the period number tells you the number of occupied electron shells.
元素周期表按原子序数递增的顺序排列元素，并根据相似的化学性质进行分组。纵列称为族；同一族的元素具有相同的最外层电子数，这解释了它们具有相似的反应活性。例如，第1族金属（碱金属）都非常活泼，形成1+ 离子；而第7族元素（卤素）是活泼的非金属，形成1− 离子。横排称为周期，周期数告诉你电子层占据的层数。
Group 0 (noble gases) are very stable and unreactive because they have a full outer shell of electrons. This principle links to the idea that atoms tend to gain, lose or share electrons to achieve a stable electron arrangement, a key concept when studying chemical bonding.
第0族（稀有气体）非常稳定且不活泼，因为它们具有排满的最外层电子。这一原理联系到原子倾向于通过得失或共用电子来达到稳定电子排布的思想，这是学习化学键的核心概念。
4. Chemical Reactions and Energy Changes | 化学反应与能量变化
A chemical reaction involves the rearrangement of atoms to form new substances. Signs of a reaction include temperature change, colour change, gas production, or the formation of a precipitate. Word equations and symbol equations are used to summarise reactions. For instance, the combustion of methane can be written as:
化学反应涉及原子的重新排列以形成新物质。反应的迹象包括温度变化、颜色变化、产生气体或生成沉淀。可以使用文字方程式和符号方程式来归纳反应。例如，甲烷的燃烧可以表示为：
CH₄ + 2O₂ → CO₂ + 2H₂O
Reactions are either exothermic, releasing heat energy to the surroundings, or endothermic, absorbing energy. Combustion and neutralisation are typical exothermic reactions, while photosynthesis and the thermal decomposition of carbonates are endothermic. Catalysts speed up reactions without being used up, making industrial processes more efficient.
反应可以是放热反应（向环境释放热能）或吸热反应（吸收能量）。燃烧和中和是典型的放热反应，而光合作用和碳酸盐的热分解是吸热反应。催化剂能加快反应速率而自身不被消耗，从而提高工业过程的效率。
5. Forces, Speed, and Newton’s Laws | 力、速度与牛顿定律
Forces can change the shape, speed, or direction of an object. Common forces include weight, friction, tension, and air resistance. The average speed of a moving object is calculated using the equation:
力可以改变物体的形状、速度或方向。常见的力包括重力、摩擦力、张力和空气阻力。运动物体的平均速度可用下列方程式计算：
speed = distance ÷ time (v = d / t)
Measured in metres per second (m/s), distance in metres (m) and time in seconds (s). Newton’s First Law states that an object will remain at rest or continue moving at constant velocity unless acted upon by an unbalanced force. Newton’s Second Law links force, mass, and acceleration: F = ma, where force is in newtons (N).
速度单位为米每秒（m/s），距离以米（m）为单位，时间以秒（s）为单位。牛顿第一定律指出，除非受到不平衡力的作用，否则物体将保持静止或匀速直线运动。牛顿第二定律将力、质量和加速度联系起来：F = ma，其中力的单位是牛顿（N）。
Friction is a resistive force that opposes motion and can generate heat. Reducing friction with lubricants or streamlining is important in many real-world applications. Unbalanced forces cause acceleration, while balanced forces result in no change in motion.
摩擦力是一种阻碍运动的阻力，会产生热量。在许多实际应用中，使用润滑剂或流线型设计来减少摩擦力非常重要。不平衡的力会导致加速度，而平衡的力则不会引起运动状态的改变。
6. Energy Types, Transfers, and Efficiency | 能量类型、转换与效率
Energy exists in various forms: kinetic, chemical, thermal, gravitational potential, elastic potential, light, and sound. The law of conservation of energy states that energy cannot be created or destroyed, only transferred or transformed from one type to another. When a ball is thrown upwards, kinetic energy is converted into gravitational potential energy; as it falls, the reverse happens.
能量以多种形式存在：动能、化学能、热能、重力势能、弹性势能、光能和声能。能量守恒定律指出，能量既不能被创造也不能被消灭，只能从一种类型转移到或转换为另一种类型。当球向上抛出时，动能转化为重力势能；下落时则相反。
In any energy transfer, some energy is often dissipated as heat, reducing the useful output. Efficiency is calculated as:
在任何能量转换过程中，部分能量通常以热的形式散失，降低了有用输出。效率计算如下：
efficiency = (useful output energy ÷ total input energy) × 100%
Understanding efficiency helps in designing appliances and systems that minimise energy waste, for example, LED lights versus filament bulbs.
理解效率有助于设计减少能量浪费的电器和系统，例如LED灯与白炽灯泡的比较。
7. Electrical Circuits and Ohm’s Law | 电路与欧姆定律
An electric circuit requires 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), measured in ohms (Ω), opposes the flow of current. These quantities are related by Ohm’s Law:
电路需要一个完整的回路才能使电流流动。电流（I）是电荷流动的速率，以安培（A）为单位。电压（V）是每单位电荷转移的能量，以伏特（V）为单位。电阻（R）以欧姆（Ω）为单位，阻碍电流的流动。这些量由欧姆定律关联：
V = I × R
In a series circuit, current is the same everywhere while voltage divides across components. In a parallel circuit, voltage is the same across each branch, but current splits. Components such as fixed resistors, variable resistors, and diodes behave differently; a diode allows current to flow in one direction only.
在串联电路中，各处电流相同，而电压在各元件之间分配。在并联电路中，各支路两端电压相等，但电流分流。固定电阻器、可变电阻器和二极管等元件的特性不同；二极管只允许电流沿一个方向流动。
8. Waves, Sound, and Light | 波、声音与光
Waves transfer energy without transferring matter. Transverse waves, such as light and water ripples, have oscillations perpendicular to the direction of energy travel. Longitudinal waves, such as sound, have oscillations along the same direction. All waves can be described by their wavelength (λ), frequency (f), amplitude, and speed (v), connected by the wave equation:
波传递能量而不传递物质。横波（如光波和水波纹）的振动方向与能量传播方向垂直。纵波（如声波）的振动方向与传播方向相同。所有波都可以用波长（λ）、频率（f）、振幅和波速（v）来描述，并由波动方程关联：
v = fλ
s in a vacuum and can be reflected and refracted. The electromagnetic spectrum arranges waves from radio waves (longest wavelength) to gamma rays (shortest wavelength), with visible light in the middle.
声音在固体中传播最快，不能在真空中传播。光在真空中大约以 3.0 × 10⁸ m/s 的速度传播，并可以发生反射和折射。电磁波谱按波长从最长（无线电波）到最短（伽马射线）排列，可见光位于中间。
9. Ecosystems, Food Chains, and Nutrient Cycles | 生态系统、食物链与营养循环
An ecosystem is a community of living organisms interacting with their non-living environment. Energy enters most ecosystems through sunlight captured by producers (plants and algae) during photosynthesis. Food chains show the transfer of energy from producers to primary consumers, secondary consumers, and top predators. Arrows indicate the direction of energy flow.
生态系统是生物群落与其非生物环境相互作用的整体。能量通过生产者（植物和藻类）在光合作用中捕获阳光进入大多数生态系统。食物链显示了能量从生产者传递到初级消费者、次级消费者和顶级捕食者的过程。箭头表示能量流动的方向。
In addition to energy, matter is recycled. The carbon cycle and nitrogen cycle illustrate how carbon and nitrogen move between the atmosphere, living organisms, and the soil. Decomposers (bacteria and fungi) play a vital role by breaking down dead material and returning nutrients to the soil, making them available for plants to use again.
除了能量，物质也在循环利用。碳循环和氮循环说明了碳和氮如何在大气、生物体和土壤之间移动。分解者（细菌和真菌）通过分解死去的生物体并将养分归还土壤，起着至关重要的作用，使养分能再次被植物利用。
10. DNA, Genes, and Inheritance | DNA、基因与遗传
Deoxyribonucleic acid (DNA) is the molecule that carries genetic information in all living cells. A gene is a short section of DNA that codes for a specific protein. Humans have 46 chromosomes arranged in 23 pairs, with one set inherited from each parent. Variations in genes, called alleles, give rise to differences in characteristics such as eye colour or blood group.
脱氧核糖核酸（DNA）是所有活细胞中携带遗传信息的分子。基因是编码特定蛋白质的一小段DNA。人类拥有46条染色体，排列成23对，一半来自父亲，一半来自母亲。基因的变异形式称为等位基因，导致了眼睛颜色或血型等特征的差异。
Some alleles are dominant and mask the effect of recessive alleles. A Punnett square can predict the probability of offspring inheriting certain traits. Genetic disorders, such as cystic fibrosis, can be inherited if both parents carry a recessive allele. Selective breeding and genetic engineering are techniques used to modify organisms for desired traits.
有些等位基因是显性的，会掩盖隐性等位基因的效应。旁氏表可以预测后代继承某些性状的概率。如果父母双方都携带隐性等位基因，遗传病（如囊性纤维化）就可能被遗传。选择性育种和基因工程是用于修饰生物以获得所需性状的技术。
11. Earth’s Materials and the Atmosphere | 地球物质与大气层
The Earth is made up of layers: a solid inner core, liquid outer core, mantle, and thin crust. Rocks are classified as igneous (formed from cooled magma or lava), sedimentary (formed from compressed sediments) and metamorphic (formed under heat and pressure). The rock cycle describes how rocks change between these types over geological time.
地球由多个层次构成：固态内核、液态外核、地幔和薄的地壳。岩石可分为火成岩（由岩浆或熔岩冷却形成）、沉积岩（由沉积物压缩形成）和变质岩（在热和压力作用下形成）。岩石循环描述了岩石在漫长的地质时期内如何在这些类型之间转变。
The atmosphere today is about 78% nitrogen and 21% oxygen, with small amounts of argon, carbon dioxide and water vapour. Human activities, especially burning fossil fuels, are increasing atmospheric CO₂ levels, contributing to global warming and climate change. Understanding these processes is essential for developing sustainable solutions.
如今的大气层大约由78%的氮气和21%的氧气组成，还有少量的氩气、二氧化碳和水蒸气。人类活动，特别是化石燃料的燃烧，正在增加大气中的CO₂浓度，导致全球变暖和气候变化。理解这些过程对于制定可持续的解决方案至关重要。
12. Human Body Systems and Health | 人体系统与健康
The human body relies on several organ systems working together. The digestive system breaks down food into small soluble molecules that can be absorbed into the blood; key organs include the stomach and small intestine. The respiratory system brings oxygen into the body and removes carbon dioxide via the lungs, where gas exchange occurs in tiny air sacs called alveoli.
人体依赖于多个器官系统协同工作。消化系统将食物分解为可溶于水的小分子，以便被血液吸收；关键器官包括胃和小肠。呼吸系统通过肺将氧气带入体内并排出二氧化碳，气体交换在称为肺泡的微小气囊中进行。
The circulatory system, composed of the heart, blood vessels, and blood, transports oxygen, nutrients, and waste products. Maintaining a healthy lifestyle – balanced diet, regular exercise, and avoiding harmful substances – supports these systems and reduces the risk of disease. Homeostasis is the body’s ability to maintain a stable internal environment, for example, by regulating temperature and blood sugar levels.
循环系统由心脏、血管和血液组成，负责运输氧气、营养物质和废物。保持健康的生活方式——均衡饮食、规律运动和避免有害物质——有助于维持这些系统的功能并降低患病风险。稳态是身体维持稳定内环境的能力，例如通过调节体温和血糖水平来实现。
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