📚 Year 12 CCEA Science: Core Knowledge Review | CCEA 12年级科学：核心知识点梳理
Mastering the CCEA Year 12 Science syllabus requires a solid understanding of key facts across Biology, Chemistry, and Physics. This article distils the core knowledge you must know for your GCSE Double Award Science exams, from cell organelles and enzymes to atomic bonding, reaction energetics, and the behaviour of waves. Each section pairs a concise explanation in English with an equivalent in Chinese, helping you build both comprehension and scientific terminology in two languages.
掌握 CCEA 12 年级科学大纲，需要对生物、化学和物理中的关键事实有扎实的理解。这篇文章提炼了你在 GCSE 双科学考试中必须掌握的核心知识，从细胞器和酶到原子键合、反应能量学以及波的特性。每一节都将简明的英文解释与中文解释配对，帮助你在两种语言中同步提升理解力和科学术语的掌握度。
1. Cell Structure and Organisation | 细胞结构与组织
All living organisms are composed of cells. Animal cells typically contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells share these structures but also possess a rigid cell wall made of cellulose, a large permanent vacuole containing cell sap, and chloroplasts for photosynthesis.
所有生物体都由细胞构成。动物细胞通常含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞除这些结构外，还具有由纤维素组成的刚性细胞壁、充满细胞液的大液泡以及进行光合作用的叶绿体。
Eukaryotic cells have genetic material enclosed in a nucleus, whereas prokaryotic cells (e.g., bacteria) lack a true nucleus and have a single loop of chromosomal DNA, along with small rings called plasmids. Organisms may be unicellular or made up of many cells organised into tissues, organs, and organ systems.
真核细胞的遗传物质被包裹在细胞核内，而原核细胞（如细菌）没有真正的细胞核，它们只有单条环状染色体 DNA 以及称为质粒的小环状 DNA。生物可以是单细胞的，也可以由许多细胞组成，这些细胞组织成组织、器官和器官系统。
- Cell differentiation allows specialised cells – such as nerve cells, sperm cells, root hair cells and xylem vessels – to perform specific functions efficiently.
- 细胞分化产生了特化的细胞——如神经细胞、精子细胞、根毛细胞和木质部导管——从而高效执行特定功能。
2. Microscopy and Size Calculations | 显微镜与大小计算
uctures at magnifications up to around ×1500. To calculate magnification, use the formula:
光学显微镜可以让我们以高达约 1500 倍的放大率观察细胞和亚细胞结构。计算放大倍数可使用以下公式：
magnification = size of image / actual size of object
rements to the same unit (e.g., micrometres) before calculating. Remember that 1 mm = 1000 µm.
如果已知放大倍数和图像大小，你可以求出细胞或细胞器的实际尺寸。计算前务必将单位统一（例如，微米）。记住 1 mm = 1000 µm。
An electron microscope has a much higher resolving power than a light microscope, allowing scientists to visualise internal structures like mitochondria and ribosomes in finer detail. However, electron microscopes cannot be used on living specimens.
电子显微镜的分辨率远高于光学显微镜，使科学家能够更精细地观察线粒体和核糖体等内部结构。但电子显微镜不能用于活体样本。
3. Enzymes and the Digestive System | 酶与消化系统
Enzymes are biological catalysts that speed up metabolic reactions without being consumed. Their active site is specific to a substrate, described by the lock-and-key model. Enzyme activity is affected by temperature and pH: each enzyme works best at an optimum temperature and pH. Denaturation occurs when the active site changes shape permanently at extremes.
酶是生物催化剂，可以加快代谢反应而自身不被消耗。它的活性部位对底物具有特异性，可用“锁钥模型”描述。酶的活性受温度和 pH 值影响：每种酶在其最适温度和 pH 下活性最高。在极端条件下，活性部位发生永久变形，导致变性。
The main digestive enzymes include amylase (breaks down starch into maltose), proteases (break down proteins into amino acids), and lipases (break down lipids into fatty acids and glycerol). Digestion occurs in the mouth, stomach, and small intestine. Bile, produced by the liver, emulsifies fats and neutralises stomach acid for intestinal enzymes.
主要的消化酶包括淀粉酶（将淀粉分解为麦芽糖）、蛋白酶（将蛋白质分解为氨基酸）和脂肪酶（将脂类分解为脂肪酸和甘油）。消化过程发生在口腔、胃和小肠中。肝脏产生的胆汁能够乳化脂肪，并中和胃酸，为肠道酶提供适宜环境。
4. The Circulatory System and Blood | 循环系统与血液
The human circulatory system consists of the heart, blood vessels, and blood. Deoxygenated blood enters the right atrium, is pumped to the right ventricle, and goes to the lungs via the pulmonary artery. Oxygenated blood returns to the left atrium, enters the left ventricle, and is pumped around the body through the aorta. Valves prevent backflow.
人体循环系统由心脏、血管和血液组成。缺氧血进入右心房，被泵入右心室，再通过肺动脉流向肺部。富氧血返回左心房，进入左心室，通过主动脉被泵送到全身。瓣膜可以防止血液倒流。
Arteries carry blood away from the heart at high pressure and have thick, elastic walls. Veins return blood to the heart and contain valves. Capillaries are one-cell-thick vessels that allow exchange of substances. Blood contains red blood cells (oxygen transport via haemoglobin), white blood cells (immune defence), platelets (clotting), and plasma (transports nutrients, hormones, and waste).
动脉将血液带离心脏，压力高，管壁厚且有弹性。静脉将血液送回心脏，内有瓣膜。毛细血管是单层细胞的薄壁血管，允许物质交换。血液含有红细胞（通过血红蛋白运输氧气）、白细胞（免疫防御）、血小板（凝血）以及血浆（运输营养、激素和废物）。
5. Photosynthesis and Plant Transport | 光合作用与植物运输
Photosynthesis is the process by which plants synthesise glucose from carbon dioxide and water, using light energy trapped by chlorophyll. The summary equation is:
光合作用是植物利用叶绿素捕获的光能，从二氧化碳和水合成葡萄糖的过程。总反应式为：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The rate of photosynthesis is limited by light intensity, carbon dioxide concentration, and temperature. At low light, the rate increases linearly; eventually another factor becomes limiting. Farmers use greenhouses to optimise these conditions.
光合作用的速率受光照强度、二氧化碳浓度和温度的限制。光弱时，速率直线上升；最终另一个因素会成为限制因素。农民使用温室来优化这些条件。
Xylem transports water and dissolved minerals upwards from roots to leaves via transpiration pull. Phloem transports dissolved sugars (mainly sucrose) in both directions – this process is called translocation. Root hair cells absorb water by osmosis and mineral ions by active transport.
木质部通过蒸腾拉力将水分和溶解的矿物质从根部向上输送到叶片。韧皮部将溶解的糖（主要是蔗糖）进行双向运输——这称为输导作用。根毛细胞通过渗透作用吸收水分，通过主动运输吸收矿质离子。
6. DNA, Genes and Inheritance | DNA、基因与遗传
DNA is a double-stranded polymer made of nucleotides, each containing a sugar, phosphate, and a base (A, T, C, G). A gene is a section of DNA that codes for a particular protein. Chromosomes, found in the nucleus, are long coils of DNA carrying many genes. Humans have 46 chromosomes (23 pairs).
DNA 是由核苷酸组成的双链聚合物，每个核苷酸包括一个糖、一个磷酸基团和一个碱基（A、T、C、G）。基因是编码特定蛋白质的 DNA 片段。染色体是位于细胞核内的长链 DNA 螺旋，携带众多基因。人类有 46 条染色体（23 对）。
Inheritance follows patterns: dominant alleles mask recessive alleles. A monohybrid cross using Punnett squares can predict genotype and phenotype ratios. Some disorders, like cystic fibrosis, are caused by recessive alleles. Sex is determined by X and Y chromosomes; females have XX, males XY.
遗传遵循一定模式：显性等位基因会掩盖隐性等位基因。使用庞纳特方格进行的单基因杂交可以预测基因型和表型的比例。一些疾病，如囊性纤维化，由隐性等位基因引起。性别由 X 和 Y 染色体决定；女性为 XX，男性为 XY。
7. Atomic Structure and the Periodic Table | 原子结构与元素周期表
All matter is made of atoms. An atom consists of a central nucleus containing protons (positive charge, mass 1) and neutrons (no charge, mass 1), with electrons (negative charge, negligible mass) arranged in energy levels or shells. The atomic number equals the number of protons; the mass number is the sum of protons and neutrons.
所有物质都由原子构成。原子包含一个中央原子核，核内有质子（带正电，质量为 1）和中子（不带电，质量为 1），电子（带负电，质量忽略不计）排布在能级或电子层中。原子序数等于质子数；质量数是质子数与中子数之和。
Elements are arranged in the Periodic Table in order of increasing atomic number. The group number tells you the number of electrons in the outer shell. Elements in the same group have similar chemical properties. Group 1 are the alkali metals (reactive), Group 7 are the halogens (reactive non-metals), and Group 0 (8) are the noble gases (inert).
元素在周期表中按原子序数递增排列。族编号告诉你最外层电子数。同族元素具有相似的化学性质。第 1 族为碱金属（活泼），第 7 族为卤素（活泼非金属），第 0 族（第 8 族）为稀有气体（惰性）。
8. Chemical Bonding and Structure | 化学键合与结构
Atoms bond to achieve a full outer shell. Ionic bonding occurs between metals and non-metals, where electrons are transferred and oppositely charged ions attract. For example, sodium chloride (NaCl) forms a giant ionic lattice with strong electrostatic forces. Ionic compounds have high melting/boiling points and conduct electricity when molten or dissolved.
原子通过键合来达到满壳层结构。离子键形成于金属和非金属之间，电子发生转移，带相反电荷的离子相互吸引。例如，氯化钠 (NaCl) 形成巨大的离子晶格，离子间存在强静电作用。离子化合物的熔沸点高，在熔融或溶解状态下可导电。
Covalent bonding occurs when non-metal atoms share pairs of electrons. Simple molecular substances like H₂O and CO₂ have strong covalent bonds within molecules but weak intermolecular forces, giving them low melting points. Giant covalent structures, such as diamond and silicon dioxide, have very high melting points due to extensive bonding networks.
共价键形成时，非金属原子之间共享电子对。像 H₂O 和 CO₂ 这样的简单分子物质，分子内共价键强，但分子间的分子间作用力弱，因此熔点低。而金刚石和二氧化硅等巨型共价结构，由于广泛的键合网络，熔点极高。
9. Reactivity Series and Electrolysis | 反应活性顺序与电解
The reactivity series orders metals by their tendency to form positive ions. Potassium, sodium, lithium, and calcium are highly reactive; zinc, iron, and copper are less reactive; gold and platinum are very unreactive. A more reactive metal can displace a less reactive metal from its compound.
反应活性顺序根据金属形成阳离子的倾向排列。钾、钠、锂和钙非常活泼；锌、铁和铜活泼性较弱；金和铂极不活泼。较为活泼的金属可以从化合物中置换出较不活泼的金属。
Electrolysis is the decomposition of an ionic compound using direct current. During electrolysis of molten substances, cations migrate to the cathode and anions to the anode. For aqueous solutions, the product depends on the ions and the electrode potential. Aluminium is extracted by electrolysis of molten aluminium oxide, with cryolite added to lower the melting point and reduce energy costs.
电解是利用直流电分解离子化合物的过程。在熔融物的电解中，阳离子移向阴极，阴离子移向阳极。对于水溶液，产物取决于离子和电极电势。铝是通过电解熔融氧化铝来提取的，并添加冰晶石以降低熔点、减少能耗。
10. Energy Changes and Reaction Rates | 能量变化与反应速率
Exothermic reactions transfer energy to the surroundings, causing a temperature rise (e.g., combustion, neutralisation). Endothermic reactions take in energy, lowering the temperature (e.g., thermal decomposition, photosynthesis). Reaction profiles show the energy of reactants and products; activation energy is the minimum energy needed to start a reaction.
放热反应将能量传递给周围环境，导致温度升高（如燃烧、中和反应）。吸热反应从环境中吸收能量，导致温度降低（如热分解、光合作用）。反应曲线图展示反应物和生成物的能量；活化能是启动反应所需的最小能量。
The rate of a reaction can be increased by raising the temperature (particles have more energy and collide more frequently), increasing concentration or pressure (more particles per unit volume), increasing surface area, or adding a catalyst. Catalysts provide an alternative pathway with lower activation energy without being used up.
提高温度（粒子能量更大，碰撞更频繁）、增大浓度或压强（单位体积粒子数增多）、增大表面积或加入催化剂，都可以提高反应速率。催化剂提供一条活化能更低的替代路径，且自身不被消耗。
11. Motion, Forces and Energy | 运动、力与能量
Speed is the rate of change of distance, and velocity includes direction. Acceleration is the rate of change of velocity. Equations you must recall include:
速率是路程变化的快慢，速度则还包括方向。加速度是速度变化的快慢。你必须熟记的公式包括：
speed = distance / time
acceleration = change in velocity / time
force = mass × acceleration (F = m × a)
Newton’s first law states that an object remains stationary or in uniform motion unless acted on by a resultant force. Newton’s second law links force, mass, and acceleration. Stopping distance is the sum of thinking distance and braking distance; each is affected by factors like speed, reaction time, and road conditions.
牛顿第一定律指出，除非受到合外力的作用，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。停车距离是反应距离与制动距离之和；两者分别受速度、反应时间和路面状况等因素影响。
Work done equals force multiplied by distance moved in the direction of the force. Kinetic energy and gravitational potential energy are given by:
功等于力乘以物体在力的方向上移动的距离。动能和重力势能的公式为：
KE = ½ × m × v²
GPE = m × g × h (g = 10 m/s² on Earth)
Energy is always conserved; it is transferred between stores but never destroyed.
能量总是守恒的；它在各能量储存库之间传递，但永远不会消失。
12. Waves, Electromagnetic Spectrum and Radioactivity | 波、电磁波谱与放射性
Waves transfer energy without transferring matter. Transverse waves (e.g., water waves, all EM waves) have oscillations perpendicular to wave travel. Longitudinal waves (e.g., sound) have oscillations parallel to the direction of travel. Key wave properties include wavelength, frequency, amplitude, and wave speed: wave speed = frequency × wavelength.
波传递能量而不传递物质。横波（如水波、所有电磁波）振动方向与波传播方向垂直。纵波（如声波）振动方向与传播方向平行。波的主要特性包括波长、频率、振幅和波速：波速 = 频率 × 波长。
aviolet, X-ray, gamma ray. All EM waves travel at the speed of light in a vacuum (3 × 10⁸ m/s). Different wavelengths have distinct uses and hazards, e.g., X-rays for medical imaging but can damage DNA.
电磁波谱按频率递增、波长递减的顺序依次为：无线电波、微波、红外线、可见光、紫外线、X 射线、伽马射线。所有电磁波在真空中以光速传播（3 × 10⁸ m/s）。不同波长有不同的用途和危害，例如 X 射线用于医学成像，但可能损伤 DNA。
Radioactive decay occurs when unstable nuclei emit alpha, beta, or gamma radiation. Alpha particles are helium nuclei (2 protons + 2 neutrons), strongly ionising but weakly penetrating. Beta particles are fast electrons, moderately ionising and penetrating. Gamma rays are electromagnetic waves, weakly ionising but highly penetrating. The half-life is the time taken for half of the radioactive nuclei in a sample to decay.
放射性衰变发生在不稳定原子核发射 α、β 或 γ 射线时。α 粒子是氦原子核（2 个质子 + 2 个中子），电离能力强但穿透力弱。β 粒子是高速电子，电离能力和穿透力中等。γ 射线是电磁波，电离能力弱但穿透力极强。半衰期是样本中一半放射性原子核衰变所需的时间。
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