Core Knowledge Review for Year 7 Cambridge Science | 剑桥七年级科学核心知识点梳理

📚 Core Knowledge Review for Year 7 Cambridge Science | 剑桥七年级科学核心知识点梳理

Welcome to the Year 7 Cambridge Science core knowledge review. This article covers key concepts across biology, chemistry, and physics, aligned with the Cambridge Lower Secondary Science Stage 7 curriculum. Use this guide to consolidate your understanding, fill in any gaps, and approach your assessments with confidence.

欢迎阅读剑桥七年级科学核心知识点梳理。本文涵盖了与剑桥初中科学阶段7课程一致的生物、化学和物理关键概念。使用这篇指南来巩固你的理解、填补知识空缺，并自信地应对评估。

1. Cells and Organisms | 细胞与生物体

All living things are made of cells. Cells are the smallest units of life and can carry out all life processes such as respiration, growth, and reproduction.

所有生物都由细胞组成。细胞是生命的最小单位，能进行呼吸、生长和繁殖等全部生命过程。

Organisms such as bacteria and amoebae are unicellular, while animals and plants are multicellular. In multicellular organisms, cells are specialised to perform different functions.

细菌和变形虫等生物是单细胞的，而动物和植物是多细胞的。在多细胞生物中，细胞分化成不同功能的特化细胞。

Plant cells contain structures not found in animal cells: a cellulose cell wall for support, chloroplasts for photosynthesis, and a large permanent vacuole filled with cell sap.

植物细胞含有动物细胞中没有的结构：起支撑作用的纤维素细胞壁、进行光合作用的叶绿体，以及充满细胞液的大液泡。

Specialised animal cells such as red blood cells (no nucleus for more haemoglobin) and nerve cells (long axon to carry impulses) are adapted to their jobs.

特化动物细胞如红细胞（无细胞核以装载更多血红蛋白）和神经细胞（长轴突传递神经冲动）都适应其特定功能。

Organelles common to both plant and animal cells include the nucleus (controls the cell), cytoplasm (where chemical reactions occur), cell membrane (controls entry and exit), and mitochondria (respiration).

动植物细胞共有的细胞器包括：细胞核（控制细胞活动）、细胞质（化学反应进行的场所）、细胞膜（控制物质进出）和线粒体（呼吸作用）。

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2. States of Matter and the Particle Model | 物质的状态与粒子模型

Matter exists in three main states: solid, liquid, and gas. The particle model describes how particles are arranged and move in each state.

物质主要以三种状态存在：固态、液态和气态。粒子模型描述了粒子在各状态下的排列和运动方式。

In solids, particles are tightly packed in a regular pattern and vibrate in fixed positions. Solids have a fixed shape and volume.

在固态中，粒子紧密排列成规则结构，只能在固定位置振动。固体有固定的形状和体积。

In liquids, particles are close together but can move past each other. Liquids have a fixed volume but take the shape of the container.

在液态中，粒子彼此靠近但能自由滑动。液体有固定的体积，但形状随容器而变。

In gases, particles are far apart and move rapidly in all directions. Gases have no fixed shape or volume and can be compressed easily.

在气态中，粒子间距很大，快速向各方向运动。气体没有固定的形状或体积，容易被压缩。

Changes of state, such as melting, boiling, condensing, and freezing, involve energy transfer. The particles themselves do not change; only their arrangement and motion change.

状态变化，如熔化、沸腾、冷凝和凝固，都涉及能量转移。粒子本身不会改变；只有它们的排列和运动方式发生变化。

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3. Atoms, Elements, and Compounds | 原子、元素与化合物

All matter is made from about 100 different types of atoms. An element is a substance made of only one type of atom, and it is represented by a chemical symbol, e.g. O for oxygen, Fe for iron.

所有物质由大约100种不同的原子构成。元素是由同种原子组成的纯物质，用化学符号表示，如 O 代表氧，Fe 代表铁。

A compound is formed when two or more different elements chemically combine. The properties of a compound are different from the elements that make it up, e.g. water (H₂O) is very different from hydrogen and oxygen.

化合物由两种或多种不同元素通过化学结合形成。化合物的性质与组成它的元素完全不同，例如水 (H₂O) 与氢和氧性质迥异。

Chemical formulas use symbols and subscript numbers to show the types and ratios of atoms, such as CO₂ (one carbon atom and two oxygen atoms) or NaCl (one sodium and one chlorine).

化学式使用符号和下标数字表示原子种类和比例，例如 CO₂（一个碳原子和两个氧原子）或 NaCl（一个钠和一个氯）。

The Periodic Table organises all known elements in order of increasing atomic number. Metals are on the left, non-metals on the right.

元素周期表按原子序数递增顺序排列所有已知元素。金属在左侧，非金属在右侧。

Common compounds you encounter include carbon dioxide (CO₂), sodium chloride (table salt), and calcium carbonate (found in limestone and chalk).

常见的化合物包括二氧化碳 (CO₂)、氯化钠（食盐）和碳酸钙（存在于石灰石和白垩中）。

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4. Mixtures and Separation Techniques | 混合物与分离技术

A mixture contains two or more substances that are not chemically combined. Unlike compounds, the components of a mixture keep their own properties and can be separated by physical methods.

混合物含有两种或多种未经过化学结合的物质。与化合物不同，混合物的各成分保持自身性质，可通过物理方法分离。

Filtration is used to separate an insoluble solid from a liquid, e.g. sand from water. The solid trapped on filter paper is the residue, and the liquid passing through is the filtrate.

过滤用于分离不溶性固体和液体，例如从水中分离沙子。滤纸上截留的固体是滤渣，穿过的液体是滤液。

Evaporation and crystallisation are used to obtain a dissolved solid (solute) from a solution. Heating evaporates the solvent, leaving the solute behind as crystals.

蒸发和结晶用于从溶液中获得溶解的固体（溶质）。加热蒸发溶剂，溶质以晶体形式留下。

Distillation separates a solvent from a solution or separates miscible liquids with different boiling points. The liquid with the lower boiling point evaporates first, then condenses.

蒸馏可分离溶剂与溶液，或分离沸点不同的互溶液体。沸点较低的液体先蒸发，然后冷凝。

Chromatography is used to separate mixtures of coloured substances, such as inks or food dyes. The substances move at different speeds across a stationary phase, producing a chromatogram.

色谱法用于分离有色物质的混合物，如墨水或食用色素。各物质在固定相上移动速度不同，产生色谱图。

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5. Forces and Motion | 力与运动

A force is a push or a pull. Forces can change the speed, direction, or shape of an object. They are measured in newtons (N).

力是推或拉的作用。力可以改变物体的速度、方向或形状。力的单位是牛顿 (N)。

When forces on an object are balanced, the object remains stationary or moves at a constant speed. Unbalanced forces cause acceleration or deceleration.

当物体受到的力平衡时，物体会保持静止或匀速运动。不平衡的力会导致加速或减速。

Friction is a force that opposes motion between two surfaces in contact. It can be useful (e.g. gripping) or unwanted (e.g. causing wear and overheating).

摩擦力是阻碍接触表面相对运动的力。它可能是有用的（如抓握），也可能是不希望的（如导致磨损和过热）。

Gravity is a non-contact force that pulls objects towards the centre of the Earth. Weight is the gravitational pull on an object’s mass and is calculated as:

重力是一种非接触力，将物体拉向地心。重量是地球对物体质量的重力拉力，计算公式为：

Weight (N) = mass (kg) × gravitational field strength (N/kg), W = m × g

重量 (N) = 质量 (kg) × 重力场强度 (N/kg)，W = m × g

On Earth, g is approximately 10 N/kg. Mass stays the same everywhere, but weight changes if gravity changes, e.g. on the Moon.

在地球上，g 约为 10 N/kg。质量在任何地方都相同，但若重力变化，重量也会改变，比如在月球上。

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6. Energy Forms and Transfers | 能量的形式与转移

Energy exists in different forms: kinetic (movement), thermal (heat), light, sound, electrical, chemical (stored in food and fuels), and gravitational potential.

能量以不同形式存在：动能（运动）、热能（热）、光能、声能、电能、化学能（储存在食物和燃料中）和重力势能。

Energy can be transferred from one store to another or from one object to another. It is never created or destroyed; this is the principle of conservation of energy.

能量可以从一个储存库转移到另一个，或从一个物体转移到另一物体。它既不能创造也不能消灭，这就是能量守恒定律。

In a torch, the energy pathway is: chemical energy in the battery → electrical energy in wires → light and thermal energy at the bulb. Some energy is always dissipated as heat.

在手电筒中，能量转移路径为：电池中的化学能 → 导线中的电能 → 灯泡处的光能和热能。部分能量总会以热的形式散失。

Food labels show energy content in kilojoules (kJ). We need energy for activity, growth, and keeping warm. Different activities require different amounts of energy.

食品标签显示以千焦 (kJ) 为单位的能量含量。我们需要能量进行活动、生长和维持体温。不同活动需要的能量不同。

Fossil fuels like coal, oil, and natural gas are non-renewable resources that store chemical energy from ancient organisms. Burning them releases energy but also carbon dioxide.

煤炭、石油和天然气等化石燃料是不可再生资源，储存了来自远古生物的化学能。燃烧它们释放能量，但也产生二氧化碳。

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7. Electricity and Circuits | 电与电路

Electric current is the flow of electric charge, usually electrons, through a conducting path. It is measured in amperes (amps, A) using an ammeter connected in series.

电流是电荷（通常是电子）通过导电路径的流动。电流的单位是安培 (A)，用串联的安培表测量。

Voltage (potential difference) is the ‘push’ that drives current around a circuit. It is measured in volts (V) using a voltmeter connected in parallel across a component.

电压（电势差）是驱动电流在电路中流动的“推力”。电压的单位是伏特 (V)，用并联在元件两端的伏特表测量。

A complete circuit needs a cell or battery, connecting wires, and a load such as a bulb or motor. If there is a break, current stops and the circuit is incomplete or open.

一个完整的电路需要电池、导线以及灯泡或马达这样的负载。如果出现断路，电流停止，电路即断开。

Series circuits have only one loop. If one component fails, the whole circuit breaks. The current is the same at all points, but voltages add up.

串联电路只有一个回路。如果一个元件损坏，整个电路断开。串联电路中各处电流相同，而电压相加。

Parallel circuits have multiple branches. Each branch receives the full voltage from the source. If one branch breaks, the others can continue to work.

并联电路有多个分支。每条支路都得到电源的全部电压。如果一条支路断开，其他支路仍可继续工作。

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8. Acids and Alkalis | 酸与碱

Acids are substances that release hydrogen ions (H⁺) in water. They taste sour and turn blue litmus paper red. Common acids include hydrochloric acid (HCl) and sulfuric acid (H₂SO₄).

酸是在水中释放氢离子 (H⁺) 的物质。它们尝起来有酸味，并使蓝色石蕊试纸变红。常见酸包括盐酸 (HCl) 和硫酸 (H₂SO₄)。

Alkalis are soluble bases that release hydroxide ions (OH⁻) in water. They feel soapy and turn red litmus paper blue. Examples are sodium hydroxide (NaOH) and potassium hydroxide (KOH).

碱是可溶性碱，在水中释放氢氧根离子 (OH⁻)。它们触感滑腻，使红色石蕊试纸变蓝。例子有氢氧化钠 (NaOH) 和氢氧化钾 (KOH)。

The pH scale (0-14) measures acidity or alkalinity. Values below 7 are acidic, 7 is neutral (pure water), and above 7 are alkaline. Indicators like universal indicator show colour changes.

pH 值标度 (0-14) 测量酸碱度。低于 7 为酸性，7 为中性（纯水），高于 7 为碱性。通用指示剂等指示剂会显示颜色变化。

Neutralisation: acid + alkali → salt + water. For example, hydrochloric acid + sodium hydroxide → sodium chloride + water. This reaction releases heat (exothermic).

中和反应：酸 + 碱 → 盐 + 水。例如，盐酸 + 氢氧化钠 → 氯化钠 + 水。该反应放热（放热反应）。

Common salts include chlorides (from hydrochloric acid), sulfates (from sulfuric acid), and nitrates (from nitric acid). The name of the salt comes from the acid and the metal in the base.

常见盐包括氯化物（来自盐酸）、硫酸盐（来自硫酸）和硝酸盐（来自硝酸）。盐的名称来源于所用的酸和碱中的金属。

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9. Earth, Rocks, and the Solar System | 地球、岩石与太阳系

The Earth is rocky and has a layered structure: a thin crust, a mostly solid mantle (with a partially molten layer), a liquid outer core, and a solid inner core of iron and nickel.

地球是岩石星球，具有分层结构：薄薄的地壳、大部分为固态的地幔（含部分熔融层）、液态外核以及铁镍组成的固态内核。

Igneous rocks form from cooled magma or lava. If cooling is slow, large crystals form (e.g. granite); if cooling is fast, crystals are small (e.g. basalt).

火成岩由冷却的岩浆或熔岩形成。缓慢冷却则形成大晶体（如花岗岩）；快速冷却则形成小晶体（如玄武岩）。

Sedimentary rocks form from compressed layers of sediment, often containing fossils. Examples are limestone, sandstone, and chalk.

沉积岩由压实的沉积物层形成，常含有化石。例如石灰岩、砂岩和白垩。

Metamorphic rocks are formed when existing rocks are changed by heat and pressure. Marble comes from limestone, and slate comes from shale.

变质岩由已有岩石在热和压力作用下变质形成。大理石源自石灰岩，板岩源自页岩。

Weathering and erosion break down rocks. Physical weathering (freeze-thaw) and chemical weathering (acid rain on limestone) are key processes. Erosion involves the movement of particles by water, wind, or ice.

风化和侵蚀使岩石破碎。物理风化（冻融作用）和化学风化（酸雨作用于石灰岩）是主要过程。侵蚀指水、风或冰搬运颗粒的过程。

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10. Sound and Light | 声音与光

Sound is produced by vibrations. These vibrations travel through a medium (solid, liquid, or gas) as longitudinal waves, causing particles to compress and rarefy.

声音由振动产生。这些振动以纵波形式在介质（固体、液体或气体）中传播，使粒子交替压缩和稀疏。

Sound cannot travel through a vacuum because there are no particles to transmit the vibrations. The speed of sound varies; it travels fastest in solids and slowest in gases.

声音不能在真空中传播，因为没有粒子传递振动。声速因介质而异，在固体中最快，在气体中最慢。

Pitch (how high or low a sound is) depends on frequency; loudness depends on amplitude. Echoes are reflected sound waves.

音调（声音的高低）取决于频率；响度取决于振幅。回声是反射回来的声波。

Light is a form of energy that travels in straight lines. When light hits a smooth surface, it reflects at the same angle (angle of incidence = angle of reflection).

光是一种沿直线传播的能量形式。光照射到光滑表面时，会以相同角度反射（入射角 = 反射角）。

Refraction occurs when light passes from one transparent medium to another (e.g. air to glass) and changes speed and direction. Lenses use refraction to focus light.

当光从一种透明介质进入另一种介质（如从空气到玻璃）时，速度改变并发生折射。透镜利用折射聚焦光线。

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