📚 Year 7 OCR Science: Core Knowledge Review | Year 7 OCR 科学：核心知识点梳理
Year 7 Science introduces students to the key ideas that form the foundation of biology, chemistry and physics. This article summarises the core knowledge for each topic, helping you to feel confident and ready for your lessons and assessments.
七年级科学课程向学生介绍了构成生物、化学和物理基础的关键概念。本文整理了每个主题的核心知识，帮助你在课堂和考试中更加自信从容。
1. Cells and Microscopy | 细胞与显微镜
All living organisms are made of cells. Cells are the smallest units of life that can carry out all the processes needed to stay alive.
所有生物都由细胞构成。细胞是能够完成维持生命所需全部过程的最小生命单位。
An animal cell contains a nucleus (controls the cell), cytoplasm (where chemical reactions happen), a cell membrane (controls what enters and leaves) and mitochondria (where respiration occurs).
动物细胞包含细胞核（控制细胞活动）、细胞质（化学反应发生的场所）、细胞膜（控制物质进出）和线粒体（进行呼吸作用的部位）。
Plant cells have the same parts plus a rigid cell wall for support, chloroplasts that capture light energy for photosynthesis, and a large permanent vacuole filled with cell sap.
植物细胞除了上述结构外，还有起支撑作用的刚性细胞壁、捕获光能进行光合作用的叶绿体，以及充满细胞液的大液泡。
We use a light microscope to view cells. The total magnification is calculated as: eyepiece lens magnification × objective lens magnification.
我们使用光学显微镜观察细胞。总放大倍数的计算方法是：目镜放大倍数 × 物镜放大倍数。
total magnification = eyepiece mag. × objective mag.
总放大倍数 = 目镜放大倍数 × 物镜放大倍数
2. Body Systems | 人体系统
Cells with a similar job group together to form tissues. Different tissues work together to make an organ, and organs work together in organ systems.
功能相似的细胞聚集形成组织。不同的组织协同工作构成器官，器官协同工作构成器官系统。
The skeleton provides support, protection (e.g. skull protects the brain) and allows movement because muscles pull on bones at joints.
骨骼提供支撑和保护（例如头骨保护大脑），并通过肌肉在关节处牵拉骨骼实现运动。
In the respiratory system, air enters through the trachea, passes into the bronchi and then bronchioles, ending in tiny air sacs called alveoli where gas exchange takes place.
在呼吸系统中，空气通过气管进入支气管和细支气管，最终到达微小的肺泡，气体交换在此进行。
The circulatory system transports oxygen, nutrients, hormones and waste products. The heart pumps blood around the body in arteries, veins and capillaries.
循环系统运输氧气、营养物质、激素和废物。心脏通过动脉、静脉和毛细血管将血液泵送至全身。
The digestive system breaks down large food molecules. Enzymes speed up this breakdown, and the small intestine absorbs small, soluble molecules into the blood.
消化系统分解大分子食物。酶会加速这一分解过程，小肠将小而可溶的分子吸收进入血液。
3. Particles and States of Matter | 粒子与物质状态
All substances are made of tiny particles. The particle model explains the properties of solids, liquids and gases.
所有物质都由微小粒子组成。粒子模型可以解释固体、液体和气体的性质。
In a solid, particles are held in fixed positions, vibrating in place. This gives solids a fixed shape and a fixed volume.
在固体中，粒子在固定位置上振动，因此固体有固定的形状和固定的体积。
In a liquid, particles are close together but can move past each other. Liquids take the shape of their container but have a fixed volume.
在液体中，粒子紧密排列但可以相互滑动，因此液体具有固定的体积但形状随容器而变。
In a gas, particles are far apart and move quickly in all directions. Gases have no fixed shape and no fixed volume; they spread out to fill any container.
在气体中，粒子间距很大，向各个方向快速运动，因此既没有固定的形状也没有固定的体积，会扩散充满整个容器。
When a substance changes state, the particles stay the same, but their arrangement and speed of movement change. Melting and boiling require energy to overcome attractions between particles.
物质状态改变时，粒子本身不变，但排列方式和运动速度发生变化。熔化和沸腾需要能量来克服粒子间的吸引力。
4. Atoms, Elements and Compounds | 原子、元素与化合物
An element is a substance made of only one type of atom. All known elements are listed in the periodic table.
元素是由同一种原子组成的物质。所有已知的元素都列在元素周期表中。
Each element has a chemical symbol; for example, O stands for oxygen, Fe for iron and Na for sodium. The first letter is always a capital.
每种元素都有一个化学符号；例如，O 代表氧，Fe 代表铁，Na 代表钠。首字母必须大写。
A compound is formed when two or more different elements chemically join together. The properties of a compound are usually very different from the elements that make it.
当两种或多种不同元素通过化学结合时，就形成了化合物。化合物的性质通常与其组成元素截然不同。
We write compound names using element names and symbols, such as carbon dioxide (CO₂) and water (H₂O). The small numbers show how many atoms of each element are in one unit.
我们用元素名称和符号书写化合物名称，例如二氧化碳 (CO₂) 和水 (H₂O)。右下角的小数字表示每个单元中各原子的数目。
5. Chemical Reactions | 化学反应
In a chemical reaction, reactants are rearranged to make new products. No atoms are created or destroyed; this is called conservation of mass.
在化学反应中，反应物经过重新排列生成新的产物。原子不会被创生或消灭，这称为质量守恒。
We can spot a reaction by observing signs such as a colour change, a gas given off (fizzing), a temperature change, or a precipitate forming.
我们可以通过观察颜色变化、产生气体（起泡）、温度变化或生成沉淀等现象来判断化学反应的发生。
A word equation shows the reactants on the left and products on the right, linked by an arrow. For example: methane + oxygen → carbon dioxide + water
文字方程式用箭头连接左侧的反应物和右侧的产物。例如：甲烷 + 氧气 → 二氧化碳 + 水
Some reactions release energy (exothermic, like burning), and some absorb energy (endothermic, like sherbet dissolving).
有些反应释放能量（放热反应，如燃烧），有些吸收能量（吸热反应，如柠檬汽水粉溶解）。
Common types of reactions include combustion (burning with oxygen), oxidation, thermal decomposition, and neutralisation between acids and alkalis.
常见的反应类型包括燃烧（与氧气反应）、氧化、热分解，以及酸与碱的中和反应。
6. Forces and Motion | 力与运动
A force is a push or a pull, measured in newtons (N). Forces can change the speed, direction or shape of an object.
力是推或拉，单位是牛顿 (N)。力可以改变物体的速度、运动方向或形状。
Contact forces (e.g. friction, air resistance) act when objects touch. Non‑contact forces (e.g. gravity, magnetic force) act at a distance.
接触力（如摩擦力、空气阻力）需要在物体接触时才能作用。非接触力（如重力、磁力）可以在一定距离外作用。
When forces on an object are balanced, the object stays at rest or continues to move at a steady speed in a straight line.
当物体上的力平衡时，物体保持静止，或继续以恒定速度沿直线运动。
Unbalanced forces cause an object to speed up, slow down or change direction. The overall effect is the resultant force.
不平衡的力会使物体加速、减速或改变运动方向，总效果就是合力。
Speed can be calculated using:
speed = distance ÷ time
速度可以用以下公式计算：
速度 = 距离 ÷ 时间
7. Energy Transfers and Stores | 能量转移与储存
Energy is never created or destroyed; it is transferred between stores. The unit of energy is the joule (J).
能量既不会创生也不会消灭，它只是在不同的能量储存之间转移。能量的单位是焦耳 (J)。
There are different energy stores: kinetic (movement), thermal (heat), chemical (food and fuels), elastic potential (stretched spring), gravitational potential (height) and nuclear.
能量有各种不同的储存形式：动能（运动）、热能、化学能（食物和燃料）、弹性势能（拉伸的弹簧）、重力势能（高度）和核能。
Energy can be transferred mechanically (by forces), electrically (when charges move), by heating (thermal conduction or radiation), or by sound and light waves.
能量可以通过机械方式（力的作用）、电力方式（电荷移动）、加热（热传导或热辐射）或通过声波与光波进行转移。
When a ball is thrown upwards, kinetic energy is transferred to gravitational potential energy. As it falls, the process reverses, and some energy dissipates as heat due to air resistance.
当球被向上抛出时，动能转化为重力势能。下落时则相反，并且由于空气阻力，部分能量以热能的形式耗散。
Machines and devices transfer energy from one store to another. The proportion of useful energy transferred is called efficiency.
机器和设备将能量从一种储存形式转换为另一种。有用的能量转移所占的比例称为效率。
8. Electricity and Circuits | 电与电路
Current is the flow of electric charge, measured in amperes (A). In a metal wire, the moving charges are electrons.
电流是电荷的流动，单位是安培 (A)。在金属导线中，移动的电荷是电子。
A complete circuit needs a power source (cell or battery), connecting wires and a component (such as a bulb or buzzer). There must be no gaps for the current to flow.
一个完整的电路需要电源（电池）、连接导线和一个用电器（如灯泡或蜂鸣器）。电路中不能有断路，电流才能流通。
In a series circuit, there is only one loop. The current is the same everywhere. Adding more bulbs makes them dimmer because each bulb shares the voltage.
串联电路中只有一个回路，各处电流相同。增加灯泡数量会使灯泡变暗，因为每个灯泡分享的电压减小。
In a parallel circuit, there is more than one loop. If one branch breaks, the others keep working. The total current from the battery splits between the branches.
并联电路中有多个回路。如果某一支路断开，其他支路仍可工作。电池提供的总电流在各支路之间分配。
Conductors (such as copper) allow charge to flow easily, while insulators (such as plastic) do not. Switches control whether a circuit is complete or broken.
导体（如铜）允许电荷容易地通过，而绝缘体（如塑料）则不行。开关用来控制电路的通断。
9. Sound and Light | 声音与光
Sound is produced when objects vibrate. The vibrations travel through a medium (solid, liquid or gas) and cannot travel through a vacuum.
声音由物体振动产生。振动通过介质（固体、液体或气体）传播，不能在真空中传播。
The frequency of a sound wave determines its pitch: a high frequency gives a high pitch. Amplitude determines how loud the sound is.
声波的频率决定音调高低：频率越高，音调越高。振幅决定声音的响度。
Light travels in straight lines at a very high speed (about 300,000 km/s in a vacuum). We see objects because light bounces off them and enters our eyes.
光沿直线传播，速度极快（真空中约为 300,000 km/s）。我们能看到物体，是因为光从物体表面反射进入眼睛。
When light hits a smooth surface, it reflects at the same angle it hits: angle of incidence = angle of reflection.
光照射到光滑表面时，反射角等于入射角。
Refraction happens when light passes from one transparent material to another and changes speed, causing it to bend. This is why a straw looks broken in water.
当光从一种透明介质进入另一种透明介质时，速度改变，光线发生弯折，这就是折射。这就是吸管在水中看起来折断的原因。
White light can be split into a spectrum of colours (red, orange, yellow, green, blue, indigo, violet) by a prism. This process is called dispersion.
白光可以通过棱镜分解为彩色光谱（红、橙、黄、绿、蓝、靛、紫），这个过程叫做色散。
10. Earth and Atmosphere | 地球与大气
The Earth has a layered structure: a solid inner core, a liquid outer core, a thick mantle and a thin rocky crust on which we live.
地球具有层状结构：固态的内核、液态的外核、厚厚的地幔以及我们生活其上的薄岩石地壳。
Rocks are classified into three main types: igneous (formed from cooled magma or lava, e.g. basalt, granite), sedimentary (made from compressed layers, e.g. limestone, sandstone) and metamorphic (changed by heat and pressure, e.g. marble, slate).
岩石主要分为三类：岩浆岩（由冷却的岩浆或熔岩形成，如玄武岩、花岗岩）、沉积岩（由压缩的沉积层形成，如石灰岩、砂岩）和变质岩（受热和压力作用变质而成，如大理石、板岩）。
The rock cycle shows how rocks can change between these types over millions of years through processes such as melting, cooling, weathering, erosion and burial.
岩石循环展示了岩石如何在数百万年间通过熔化、冷却、风化、侵蚀和埋藏等过程在三种类型之间相互转化。
The Earth’s atmosphere today is mainly nitrogen (about 78%) and oxygen (about 21%), with small amounts of other gases like carbon dioxide and argon.
今天的地球大气层主要由氮气（约 78%）和氧气（约 21%）组成，还有少量的二氧化碳和氩气等其他气体。
Photosynthesis by plants and algae over billions of years increased the oxygen level. Burning fossil fuels today releases carbon dioxide, which is linked to climate change.
数十亿年间，植物和藻类的光合作用提高了氧气含量。而如今，燃烧化石燃料会释放二氧化碳，这与气候变化相关。
11. Separating Mixtures | 混合物分离
A mixture contains two or more substances that are not chemically joined. We can separate mixtures using physical methods.
混合物含有两种或多种未发生化学结合的物质。我们可以用物理方法分离混合物。
Filtration is used to separate an insoluble solid from a liquid, e.g. sand from water. The solid left in the filter paper is the residue, and the liquid that passes 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。留在滤纸上的固体是残渣，穿过滤纸的液体是滤液。
Evaporation separates a soluble solid from a solution by heating until the liquid component turns to vapour, leaving the solid behind.
通过加热使溶液中的液体变为蒸气，留下固体，这就是蒸发，用于分离可溶性固体与溶液。
Distillation separates a solvent from a solution by boiling and then condensing the vapour, collecting the pure liquid (distillate).
蒸馏通过加热使溶剂沸腾，然后将蒸气冷凝，收集纯液体的方法，可以分离溶剂和溶液。
Chromatography separates different dissolved substances based on how far they travel up an absorbent paper. It can be used to separate the colours in ink.
色谱法根据溶解物质在吸水性纸上移动距离的不同进行分离，常用于分离墨水中的各种颜色。
12. Working Scientifically | 科学探究方法
In all investigations, we identify an independent variable (the one we change), a dependent variable (the one we measure) and control variables (the ones we keep the same).
在所有的实验探究中，我们需要确定自变量（我们改变的变量）、因变量（我们测量的变量）以及控制变量（我们保持不变的变量）。
We make a prediction and write a clear method. Results are recorded in a table before plotting a suitable graph to look for patterns or trends.
我们先提出预测，编写清晰的方法，将结果记录在表格中，然后绘制合适的图表，寻找规律或趋势。
A conclusion explains what the results show and states whether the prediction was correct. We evaluate the experiment by considering reliability, accuracy and possible improvements.
结论要解释结果说明了什么，并判断预测是否正确。我们通过考虑实验的可靠性、准确性以及可能的改进来对实验进行评价。
Using correct units (e.g., seconds, cm³, °C) and handling equipment safely (e.g., wearing goggles when heating) are essential parts of practical work.
使用正确的单位（如秒、立方厘米、摄氏度）并安全操作仪器（如加热时佩戴护目镜）是实验操作的关键部分。
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