📚 Year 7 CCEA Science: Core Knowledge Points Review | Year 7 CCEA 科学：核心知识点梳理
Welcome to your essential revision guide for Year 7 CCEA Science. This article brings together the most important concepts you will encounter in biology, chemistry and physics, helping you to build a solid foundation for Key Stage 3. Read on to clarify key ideas, check your understanding and feel confident in your science lessons.
欢迎来到 Year 7 CCEA 科学核心知识点梳理。这篇文章汇集了你在生物、化学和物理中会遇到的最重要的概念，帮助你在 Key Stage 3 建立扎实的基础。继续阅读，理清关键思路，检查你的理解，增强你在科学课上的信心。
1. Introduction to Cells | 细胞入门
All living organisms are made up of tiny building blocks called cells. Some organisms, like bacteria and amoebae, are single-celled, while plants and animals are multicellular. The two main types of cells you need to know are animal cells and plant cells. Animal cells contain a nucleus, cytoplasm, cell membrane and mitochondria. Plant cells have all of these plus a cell wall, a large central vacuole and chloroplasts. The nucleus controls the cell’s activities and contains genetic material. Cytoplasm is a jelly-like substance where chemical reactions happen. The cell membrane controls what enters and leaves the cell. Mitochondria release energy through respiration. Chloroplasts contain chlorophyll for photosynthesis, and the cell wall gives the plant cell extra support.
所有生物体都由微小的“积木”——细胞构成。有些生物，如细菌和变形虫，是单细胞的，而植物和动物是多细胞的。你需要了解的两种主要细胞类型是动物细胞和植物细胞。动物细胞包含细胞核、细胞质、细胞膜和线粒体。植物细胞除了这些，还具有细胞壁、一个大中央液泡和叶绿体。细胞核控制细胞的活动并含有遗传物质。细胞质是一种果冻状物质，化学反应在这里发生。细胞膜控制物质的进出。线粒体通过呼吸作用释放能量。叶绿体含有叶绿素进行光合作用，细胞壁为植物细胞提供额外的支撑。
Using a light microscope, we can observe and draw cells. The parts we label must be clear and accurately placed. We calculate magnification by multiplying the eyepiece lens power by the objective lens power. This allows us to view details that are invisible to the naked eye.
使用光学显微镜，我们可以观察并绘制细胞。我们必须清晰、准确地标示各部分的名称。我们通过目镜放大倍数乘以物镜放大倍数来计算总放大率，这样就能看到肉眼看不见的细节。
2. States of Matter and the Particle Model | 物质状态与粒子模型
Matter exists in three main states: solid, liquid and gas. The particle model helps us explain their properties. In solids, particles are packed closely together in a fixed arrangement, vibrating in place. That is why solids have a definite shape and volume. In liquids, particles are still close but can slide past each other, so liquids take the shape of their container but have a fixed volume. In gases, particles are far apart and move quickly in all directions, so gases have no fixed shape or volume and can be compressed easily. Changes of state – melting, freezing, boiling, condensation and sublimation – can be explained by adding or removing energy to alter particle movement.
物质以三种主要状态存在：固态、液态和气态。粒子模型帮助我们解释它们的性质。在固体中，粒子紧密排列在固定的位置上，在原地振动，因此固体有固定的形状和体积。在液体中，粒子仍然靠近，但可以相互滑动，所以液体能随容器形状而变，但体积固定。在气体中，粒子相距很远，向各个方向快速运动，所以气体没有固定的形状和体积，并且容易被压缩。物质状态的变化——熔化、凝固、沸腾、凝华和升华——都可以通过增加或减少能量来改变粒子运动来解释。
A key point is that mass is conserved during a change of state; the number of particles stays the same. We also use the terms ‘melting point’ and ‘boiling point’ to describe the temperatures at which a solid turns into a liquid, and a liquid into a gas. Water, for instance, melts at 0°C and boils at 100°C at normal pressure.
一个关键点是，状态变化时质量守恒，粒子的数量保持不变。我们还使用“熔点”和“沸点”来描述固体转化为液体、液体转化为气体的温度。例如，水在常压下熔点为0°C，沸点为100°C。
3. Energy Types and Transfers | 能量类型与转化
Energy is the ability to do work. It comes in many forms, including kinetic (movement), thermal (heat), light, sound, electrical, chemical, elastic potential and gravitational potential energy. Energy cannot be created or destroyed; it can only be transferred from one store to another, or from one form to another. This is the principle of conservation of energy. For example, when you switch on a lamp, electrical energy is transferred into light and thermal energy. In a roller coaster, gravitational potential energy at the top is converted into kinetic energy as it rushes downhill.
能量是做功的能力。它有多种形式，包括动能（运动）、热能（热）、光能、声能、电能、化学能、弹性势能和重力势能。能量不能被创造或消灭，它只能从一个能量库转移到另一个，或从一种形式转化为另一种形式。这就是能量守恒定律。例如，当你打开一盏灯，电能被转化为光能和热能。在过山车上，最高点的重力势能在下滑时转化为动能。
Energy transfers can be shown in flow diagrams or Sankey diagrams. Wasted energy is usually given off as thermal energy to the surroundings. Understanding energy transfers helps us design more efficient devices and reduce energy loss.
能量转化可以用流程图或桑基图表示。浪费的能量通常以热能的形式散发到周围环境中。了解能量转化有助于我们设计更高效的设备并减少能量损失。
4. 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) using a force meter. Common forces include gravity, friction, air resistance, upthrust and magnetic force. Gravity pulls objects towards the centre of the Earth – we call this force weight. The weight of an object depends on its mass and the strength of gravity. Friction acts between surfaces that slide past each other, opposing motion and often producing heat.
力是一种推或拉，可以改变物体的速度、方向或形状。力以牛顿（N）为单位，用测力计测量。常见的力有重力、摩擦力、空气阻力、浮力和磁力。重力将物体拉向地心——我们称其为重量。物体的重量取决于它的质量和重力大小。摩擦力作用于相互滑动的表面之间，阻碍运动并常常产生热量。
When forces on an object are balanced, the object remains stationary or moves at a steady speed. Unbalanced forces cause a change in motion – acceleration, deceleration or a change of direction. Drawing force arrow diagrams helps us model forces acting on an object; the length of the arrow shows the size of the force, and the direction shows the direction.
当作用在物体上的力平衡时，物体会保持静止或匀速运动。不平衡的力会导致运动状态改变——加速、减速或方向改变。画力箭头图可以帮助我们对作用在物体上的力进行建模；箭头的长度表示力的大小，方向表示力的方向。
5. Electric Circuits | 电路
An electric current is a flow of electric charge, usually carried by electrons moving through a wire. For a current to flow, you need a complete circuit with a power source, such as a cell or battery, and components connected by conducting wires. Common symbols are used to draw circuit diagrams: a cell, a battery (two or more cells), a lamp, a switch and a resistor. A series circuit has one single loop, so the current is the same everywhere. If one component breaks, the circuit is open and all components stop working.
电流是电荷的流动，通常由电子在导线中移动而形成。要产生电流，你需要一个完整的回路，包括电源（如电池）和由导线连接起来的元件。我们使用常见的符号来画电路图：电池、电池组（两个或以上电池）、灯泡、开关和电阻。串联电路只有一个回路，所以各处电流相同。如果一个元件损坏，电路断开，所有元件都会停止工作。
We can measure current with an ammeter placed in series, and voltage (potential difference) with a voltmeter placed in parallel across a component. Good conductors, such as copper, allow current to flow easily, while insulators, such as plastic, do not. Adding more cells increases the voltage and can make lamps brighter; adding more lamps in series increases resistance and makes them dimmer.
我们可以用串联的安培表测量电流，用并联在元件两端的伏特表测量电压（电位差）。良好的导体，如铜，允许电流轻易通过，而绝缘体，如塑料，则不导电。增加电池可以提高电压，使灯泡更亮；串联更多的灯泡会增加电阻，使它们变暗。
6. Acids and Alkalis | 酸与碱
Substances can be classified as acidic, alkaline or neutral. We use the pH scale to measure how acidic or alkaline a solution is. The scale runs from 0 to 14: acids have a pH less than 7, neutral substances (like pure water) have a pH of 7, and alkalis have a pH greater than 7. Common laboratory acids include hydrochloric acid, sulfuric acid and nitric acid. Common household alkalis include sodium hydroxide (in drain cleaner) and ammonia solution.
物质可以分为酸性、碱性或中性。我们用pH标度来衡量溶液的酸碱性。标度范围为0到14：酸的pH小于7，中性物质（如纯水）的pH为7，碱的pH大于7。常见的实验室酸有盐酸、硫酸和硝酸。家庭中常见的碱有氢氧化钠（存在于下水道清洁剂中）和氨水。
Indicators are chemicals that change colour to show whether a solution is acidic or alkaline. Litmus paper turns red in acid and blue in alkali. Universal indicator gives a range of colours across the pH scale, allowing us to estimate a numerical pH value. Neutralisation occurs when an acid and an alkali react together, producing a salt and water. For example: hydrochloric acid + sodium hydroxide → sodium chloride + water. This reaction is very useful in everyday life, from treating indigestion to controlling soil acidity.
指示剂是能通过颜色变化显示溶液是酸性还是碱性的化学品。石蕊试纸在酸中变红，在碱中变蓝。通用指示剂在pH标度上呈现一系列颜色，让我们可以估算pH数值。当中和发生时，酸和碱反应生成盐和水。例如：盐酸 + 氢氧化钠 → 氯化钠 + 水。这个反应在日常生活中非常有用，从治疗消化不良到控制土壤酸度都有应用。
7. The Human Digestive System | 人体消化系统
The human body needs nutrients for energy, growth and repair. Digestion is the process of breaking down large, insoluble food molecules into small, soluble ones that can be absorbed into the blood. Digestion begins in the mouth, where teeth mechanically break up food and saliva contains an enzyme that starts breaking down starch. The food then travels down the oesophagus to the stomach. Here, acid kills bacteria, and enzymes begin digesting proteins. The food then passes into the small intestine, where most chemical digestion and absorption of nutrients takes place. The inner walls of the small intestine are covered in tiny finger-like villi, increasing the surface area for absorption.
人体需要营养来提供能量、促进生长和修复。消化是将大的、不溶的食物分子分解成小的、可溶的分子，以便被吸收进入血液的过程。消化从口腔开始，牙齿机械地粉碎食物，唾液中含有开始分解淀粉的酶。然后食物通过食道进入胃。在胃里，酸能杀死细菌，酶开始消化蛋白质。之后食物进入小肠，大部分化学消化和营养吸收都在这里进行。小肠内壁布满了微小的手指状绒毛，以增加吸收的表面积。
Undigested food moves into the large intestine, where water is absorbed, and the remaining waste is stored in the rectum before being removed from the body. The liver and pancreas produce important digestive juices and help regulate nutrients. We should eat a balanced diet containing carbohydrates, proteins, fats, vitamins, minerals, fibre and water to keep the digestive system healthy.
未被消化的食物进入大肠，水分被吸收，剩余的废物在直肠中储存后排出体外。肝脏和胰腺产生重要的消化液，并帮助调节营养。我们应该均衡饮食，摄入碳水化合物、蛋白质、脂肪、维生素、矿物质、纤维和水，以保持消化系统健康。
8. Respiration and Breathing | 呼吸作用与呼吸
Breathing and respiration are not the same thing. Breathing (ventilation) is the mechanical movement of air into and out of the lungs. Respiration is a chemical process that occurs inside cells, releasing energy from glucose. The word equation for aerobic respiration is: glucose + oxygen → carbon dioxide + water (+ energy). Respiration provides the energy needed for all life processes, such as growth, movement and keeping warm. Breathing brings oxygen into the lungs, where it diffuses into the blood, and removes carbon dioxide.
呼吸动作和呼吸作用不是一回事。呼吸（通气）是空气进出肺部的机械运动。呼吸作用是发生在细胞内部的化学过程，从葡萄糖中释放能量。有氧呼吸的文字方程式为：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。呼吸作用为所有生命过程提供能量，如生长、运动和保温。呼吸动作将氧气带入肺部，氧气扩散进入血液，并将二氧化碳排出。
The main organs of the breathing system include the trachea, bronchi, bronchioles and alveoli. The alveoli are tiny air sacs surrounded by capillaries, allowing efficient gas exchange. During inhalation, the diaphragm contracts and rib muscles lift the ribs, making the chest volume larger and drawing air in. During exhalation, the diaphragm relaxes, ribs move down and air is pushed out. Smoking damages the alveoli and cilia, reducing the efficiency of the breathing system.
呼吸系统的主要器官包括气管、支气管、细支气管和肺泡。肺泡是被毛细血管包围的微小气囊，能高效地进行气体交换。吸气时，膈肌收缩，肋间肌上提肋骨，胸腔容积增大，空气被吸入。呼气时，膈肌放松，肋骨下降，空气被排出。吸烟会损害肺泡和纤毛，降低呼吸系统的效率。
9. Ecosystems and Food Chains | 生态系统与食物链
An ecosystem is made up of all the living organisms in an area, interacting with each other and their non-living environment. The organisms can be divided into producers, consumers and decomposers. Producers, such as green plants and algae, make their own food through photosynthesis. Consumers eat other organisms to obtain energy. A food chain shows the transfer of energy from one organism to another, always starting with a producer. For example: grass → rabbit → fox. Each step in a food chain is called a trophic level.
生态系统由一个区域内的所有生物组成，它们相互作用，并与非生物环境互相影响。生物可以分成生产者、消费者和分解者。生产者，如绿色植物和藻类，通过光合作用制造自己的食物。消费者捕食其他生物以获取能量。食物链展示了能量从一个生物到另一个生物的传递，总是从生产者开始。例如：草 → 兔子 → 狐狸。食物链中的每一步称为一个营养级。
Energy is lost at each trophic level, mostly as heat, so food chains are usually short. Decomposers, like bacteria and fungi, break down dead plants and animals, returning nutrients to the soil. The arrows in a food chain show the direction of energy flow. Changes in an ecosystem, such as a decrease in a producer population, can affect all other organisms. We also use food webs to show the more complex feeding relationships between many organisms in a habitat.
能量在每个营养级都会损失，主要以热的形式散失，所以食物链通常较短。分解者，如细菌和真菌，分解死去的动植物，让养分回归土壤。食物链中的箭头表示能量流动的方向。生态系统中的变化，例如生产者数量减少，会影响到所有其他生物。我们还使用食物网来展现栖息地中许多生物之间更复杂的捕食关系。
10. The Solar System and Beyond | 太阳系与宇宙
Our Solar System consists of the Sun, the eight planets and their moons, dwarf planets, asteroids and comets. The order of the planets from the Sun is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The inner four planets are rocky, while the outer four are gas giants. The Sun is a star at the centre, and its gravity holds the Solar System together. It provides the light and heat that make life on Earth possible.
我们的太阳系由太阳、八大行星及其卫星、矮行星、小行星和彗星组成。行星按离太阳由近到远的顺序是：水星、金星、地球、火星、木星、土星、天王星和海王星。内侧四颗行星是岩质行星，外侧四颗是气态巨行星。太阳是居于中心的恒星，其引力将太阳系维系在一起。它提供的光和热使地球上的生命成为可能。
The Earth rotates on its axis once every 24 hours, giving us day and night. The Earth orbits the Sun once every 365¼ days, producing a year and, along with the tilt of the axis, the seasons. The Moon is Earth’s natural satellite, orbiting the Earth roughly every 28 days. Its phases change because we see different amounts of the sunlit side. Beyond our Solar System, there are billions of other stars in our galaxy, the Milky Way, and countless other galaxies in the Universe. Scientists use telescopes and space probes to explore these distant objects.
地球每24小时自转一圈，形成昼夜。地球每365¼天绕太阳公转一圈，形成一年，并结合地轴的倾斜形成四季。月球是地球的天然卫星，大约每28天绕地球运行一圈。月相的变化是因为我们看到了不同面积的被阳光照亮的部分。在太阳系之外，我们的银河系中有数十亿颗其他恒星，宇宙中还有无数个星系。科学家使用望远镜和太空探测器去探索这些遥远的天体。
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