📚 Year 7 WJEC Science: Core Concepts Revision | Year 7 WJEC 科学：核心知识点梳理
Welcome to your complete revision guide for Year 7 WJEC Science. This article gathers the essential knowledge you have studied throughout the year, organised into ten clear topics. Every section presents key ideas in both English and Chinese so you can reinforce your understanding and feel confident before any assessment. Use this resource to review core concepts, check your recall and identify areas where you need a little extra practice.
欢迎使用 Year 7 WJEC 科学的完整复习指南。本文整理了你一学年学习的必备知识，分为十个清晰的专题。每个小节都以中英双语呈现核心要点，帮助你巩固理解，在任何测评前建立信心。请利用这份资料回顾关键概念、检验记忆，并找出需要额外练习的部分。
1. Working Scientifically | 科学探究方法
Scientists use a structured approach called the scientific method to explore questions and test ideas. This process usually begins with a question or observation, followed by a hypothesis — a testable prediction — and then a carefully designed experiment to collect data.
科学家使用一种称为科学方法的结构化方式来探索问题并验证想法。这个过程通常始于一个问题或观察，接着提出假设——一个可检验的预测——然后设计严谨的实验来收集数据。
In any experiment you need to identify three types of variables. The independent variable is the factor you change deliberately. The dependent variable is what you measure or observe. Control variables are all the other factors you keep the same to make your test fair.
在任何实验中你都需要识别三种变量。自变量是你有意改变的因素。因变量是你测量或观察的结果。控制变量是你为了公平测试而保持相同的所有其他因素。
Data from an investigation should be recorded in a clear table and then displayed in an appropriate graph. For continuous data a line graph or scatter graph is used; for categories a bar chart is best. Always label axes with the quantity and unit, use an even scale and give your graph a title.
实验数据应该记录在清晰的表格中，然后用合适的图表呈现。对于连续数据使用折线图或散点图；对于类别数据条形图最佳。务必用物理量和单位标注坐标轴，使用均匀刻度，并给图表加上标题。
Safety is the first priority in any laboratory. You must wear eye protection when using chemicals or heating substances, tie back long hair, and follow your teacher's instructions carefully. Always report spills or breakages at once.
实验室安全永远是第一位的。使用化学品或加热物质时必须佩戴护目镜，扎起长发，并认真听从老师的指导。发生溢出或破损应立即报告。
2. Cells – The Building Blocks of Life | 细胞——生命的基石
All living organisms are made of cells. Most animal cells have a nucleus that controls the cell's activities, cytoplasm where chemical reactions occur, a cell membrane that controls what enters and exits, and mitochondria where respiration releases energy.
所有生物体都由细胞构成。大多数动物细胞拥有控制细胞活动的细胞核、发生化学反应的细胞质、控制物质进出的细胞膜以及通过呼吸作用释放能量的线粒体。
Plant cells contain all the parts found in animal cells but also have three extra structures: a rigid cell wall made of cellulose for support, a large permanent vacuole filled with cell sap, and chloroplasts that absorb light energy for photosynthesis.
植物细胞包含动物细胞的所有结构，但还有三个额外的部分：由纤维素构成的坚硬细胞壁起支撑作用，充满细胞液的大液泡，以及吸收光能进行光合作用的叶绿体。
Many cells are specialised to carry out particular functions. For example, a root hair cell has a long extension to increase surface area for absorbing water and minerals. A red blood cell has no nucleus to make more room for haemoglobin, the protein that carries oxygen.
许多细胞是特化的，以执行特定功能。例如，根毛细胞有长长的突起以增大吸收水分和矿物质的表面积。红细胞没有细胞核，以便为携带氧气的血红蛋白腾出更多空间。
To observe cells we use a microscope. The total magnification is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. A specimen is placed on a slide, often with a drop of stain to make structures like the nucleus easier to see.
我们使用显微镜观察细胞。总放大倍数等于目镜放大倍数乘以物镜放大倍数。标本放在载玻片上，通常滴加一滴染液，使细胞核等结构更易观察。
3. Classification of Living Things | 生物的分类
Biologists classify organisms to make them easier to identify and study. The largest groups are called kingdoms. The five-kingdom system divides life into Animals, Plants, Fungi, Protoctists (single-celled organisms) and Prokaryotes (bacteria).
生物学家对生物进行分类，以便更容易识别和研究。最大的类群称为界。五界系统将生命分为动物界、植物界、真菌界、原生生物界（单细胞生物）和原核生物界（细菌）。
Within each kingdom organisms are sorted into smaller groups: phylum, class, order, family, genus and species. The scientific name of an organism is its genus and species, written in italics or underlined — for example, Homo sapiens for humans.
每个界内的生物再被划分到更小的类群：门、纲、目、科、属、种。生物的学名由其属名和种名构成，用斜体或下划线书写——例如，人类的学名是 Homo sapiens。
A species is a group of similar organisms that can breed together to produce fertile offspring. You can use a dichotomous key, a series of paired statements about observable features, to identify unknown organisms one step at a time.
物种是一群相似的生物，它们能够相互交配并产生可育后代。你可以使用二分法检索表，即一系列关于可观察特征的成对陈述，逐步鉴定未知生物。
4. Particle Theory and States of Matter | 粒子理论与物质状态
The particle model explains the behaviour of solids, liquids and gases. All matter is made of tiny particles that are constantly moving. In a solid the particles are packed in a fixed, regular arrangement and can only vibrate; solids have a fixed shape and volume.
粒子模型解释了固体、液体和气体的行为。所有物质都由不断运动的微小粒子组成。在固体中，粒子紧密排列在固定的规则位置上，只能振动；固体有固定的形状和体积。
In a liquid the particles are still close together but can slide past each other, so a liquid takes the shape of the bottom of its container and has a fixed volume. In a gas the particles are far apart, move quickly in all directions, and fill any available space; gases have no fixed shape or volume.
在液体中，粒子仍然紧靠在一起但能相互滑动，因此液体随容器底部形状而变，并具有固定的体积。在气体中，粒子相距很远，快速向各个方向运动，并充满所有可用空间；气体没有固定的形状或体积。
Changes of state — melting, freezing, boiling, evaporation and condensation — happen when energy is transferred to or from a substance. The temperature stays constant during a state change even though heating continues; this energy breaks or forms bonds between particles.
状态变化——熔化、凝固、沸腾、蒸发和凝结——发生在能量传递给物质或从物质传出时。在状态变化期间即使持续加热，温度也保持不变；这些能量用于破坏或形成粒子间的结合。
Diffusion is the movement of particles from a region of higher concentration to one of lower concentration. It occurs fastest in gases, more slowly in liquids, and does not happen in solids because the particles cannot move from place to place.
扩散是粒子从高浓度区域向低浓度区域运动的过程。扩散在气体中最快，在液体中较慢，在固体中不会发生，因为粒子无法从一个位置移动到另一位置。
5. Atoms, Elements and Compounds | 原子、元素与化合物
Every substance is made of atoms. An element is a pure substance containing only one type of atom. All known elements are arranged in the periodic table, where each element has a unique chemical symbol — for example, O for oxygen and Fe for iron.
每种物质都由原子构成。元素是只含一种原子的纯净物。所有已知元素都排列在元素周期表中，每种元素都有独一无二的化学符号——例如，氧是 O，铁是 Fe。
Atoms themselves are made of smaller subatomic particles: protons and neutrons in the nucleus, and electrons orbiting the nucleus. An atom has the same number of protons and electrons, so it has no overall charge.
原子本身由更小的亚原子粒子组成：原子核中的质子和中子，以及绕核运动的电子。原子的质子数和电子数相等，因此整体不带电。
When two or more different elements combine chemically, they form a compound. The properties of a compound are usually very different from those of the elements that make it. We represent compounds with chemical formulae, such as H₂O for water and CO₂ for carbon dioxide.
当两种或多种不同元素通过化学方式结合，就形成化合物。化合物的性质通常与组成它的元素性质截然不同。我们用化学式表示化合物，例如水是 H₂O，二氧化碳是 CO₂。
A mixture contains two or more substances that are not chemically bonded and can be separated by physical methods such as filtration, evaporation, distillation or chromatography.
混合物包含两种或多种未发生化学结合的物质，可以通过过滤、蒸发、蒸馏或色谱法等物理方法分离。
6. Chemical Reactions | 化学反应
In a chemical reaction, reactants are rearranged to form new products. You can often spot a reaction by a colour change, temperature change, gas production (bubbles or fizzing) or the formation of a precipitate (a solid appearing in a liquid).
在化学反应中，反应物重新排列形成新的产物。通常可以通过颜色变化、温度变化、产生气体（气泡或嘶嘶声）或生成沉淀（液体中出现固体）来识别反应。
rd equation: hydrochloric acid + sodium hydroxide → sodium chloride + water. This is a neutralisation reaction.
文字方程式表示反应中的反应物和产物。例如，盐酸与氢氧化钠反应生成氯化钠和水，其文字方程式为：盐酸 + 氢氧化钠 → 氯化钠 + 水。这是一个中和反应。
Acids have a pH less than 7, alkalis (soluble bases) have a pH greater than 7, and pure water has a pH of 7, which is neutral. You can measure pH using universal indicator or a pH probe.
酸的 pH 小于 7，碱（可溶性的碱）的 pH 大于 7，纯水的 pH 为 7，呈中性。你可以使用通用指示剂或 pH 计测量 pH。
Combustion, or burning, is a reaction in which a fuel reacts with oxygen, releasing energy as heat and light. Complete combustion of a hydrocarbon fuel produces carbon dioxide and water. Rusting is a slower reaction between iron, oxygen and water.
燃烧是一种燃料与氧气发生的反应，释放出热和光的能量。碳氢燃料的完全燃烧产生二氧化碳和水。生锈是铁与氧气和水发生的较慢反应。
7. 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. Contact forces, like friction and air resistance, occur when objects touch; non-contact forces, such as gravity and magnetism, act at a distance.
力是能改变物体速度、方向或形状的推或拉。力的单位是牛顿（N），使用测力计测量。接触力（如摩擦力和空气阻力）在物体接触时产生；非接触力（如重力和磁力）在一定距离外也能作用。
When forces on an object are balanced, the object remains stationary or moves at a constant speed. Unbalanced forces cause an object to accelerate, decelerate or change direction. This is summarised by Newton's First Law of Motion.
当物体受力平衡时，物体会保持静止或匀速直线运动。不平衡的力会使物体加速、减速或改变方向。这就是牛顿第一运动定律的概述。
how fast something moves. It can be calculated using: speed = distance ÷ time. A distance– y, a straight sloping line means constant speed, and a steeper slope means a higher speed.
速度表示物体运动的快慢。计算公式为：速度 = 距离 ÷ 时间。距离–时间图可以显示运动状态：水平线表示静止，倾斜直线表示匀速运动，斜率越大速度越高。
8. Energy Stores and Transfers | 能量的储存与转移
Energy is never created or destroyed; it is only transferred between stores. The main energy stores you need to know are: kinetic (movement), thermal (heat), chemical (in fuels, food and batteries), elastic potential (stretched or compressed objects), gravitational potential (objects raised above the ground) and nuclear.
能量既不会凭空产生也不会消失，它只在不同储存库之间转移。你需要掌握的主要能量储存有：动能（运动）、热能（热量）、化学能（燃料、食物和电池中）、弹性势能（拉伸或压缩的物体）、重力势能（被举高的物体）以及核能。
Energy can be transferred by four pathways: by forces doing work, by electric current, by heating, or by radiation (such as light and sound). When you lift a book onto a shelf, your muscles do work, transferring chemical energy to gravitational potential energy.
能量可以通过四条途径转移：通过作用力做功、通过电流、通过加热，或通过辐射（如光和声）。当你把一本书放到架子上时，你的肌肉做功，将化学能转移为重力势能。
Power is the rate at which energy is transferred. It is measured in watts (W). A 60 W light bulb transfers 60 joules of energy every second. Fossil fuels, such as coal, oil and natural gas, are non-renewable energy resources, whereas solar, wind and hydroelectric power are renewable.
功率是能量转移的速率，单位是瓦特（W）。一个 60 W 的灯泡每秒转移 60 焦耳的能量。煤、石油和天然气等化石燃料是不可再生能源，而太阳能、风能和水能是可再生的。
9. Electricity and Circuits | 电与电路
An electric circuit needs a complete loop for current to flow. Basic circuit components include cells (or batteries) that provide energy, wires, switches, bulbs, buzzers and motors. The standard symbols for these components must be drawn accurately in circuit diagrams.
电路需要完整的回路才能使电流流动。基本电路元件包括提供能量的电池、导线、开关、灯泡、蜂鸣器和电动机。在电路图中必须准确绘制这些元件的标准符号。
Current is the flow of electric charge and is measured in amperes (A) using an ammeter connected in series. Voltage (potential difference) is the push that drives the current, measured in volts (V) using a voltmeter connected in parallel.
电流是电荷的流动，用串联的安培计测量，单位是安培（A）。电压（电势差）是驱动电流的推力，用并联的伏特计测量，单位是伏特（V）。
In a series circuit there is only one loop, so the current is the same everywhere. Adding more bulbs increases the resistance, making each bulb dimmer. In a parallel circuit there are multiple branches; each branch gets the full voltage, so bulbs stay bright regardless of how many are added.
在串联电路中只有一条回路，因此各处电流相同。增加更多灯泡会使电阻增大，每个灯泡变暗。在并联电路中有多条支路；每条支路获得全额电压，因此不论添加多少灯泡，灯泡都保持明亮。
Conductors, such as copper, allow electric current to flow easily because they have free electrons. Insulators, like plastic and rubber, do not allow current to pass. Safety rules include never using electrical devices near water and not overloading sockets.
导体（如铜）因为有自由电子，允许电流容易通过。绝缘体（如塑料和橡胶）不允许电流通过。安全规则包括不要在近水处使用电器，以及不要让插座过载。
10. The Earth and Beyond | 地球与太空
The Earth has a layered structure: a thin, solid crust; a thick mantle of semi-solid rock that moves very slowly; a liquid outer core made of iron and nickel; and a solid inner core at the very centre, where temperatures are extreme.
地球具有层状结构：薄而坚固的地壳；由半固态岩石组成的厚厚地幔，运动非常缓慢；由铁和镍构成的液态外核；以及位于正中心的固态内核，温度极高。
Rocks are classified into three main types. Igneous rocks form when magma or lava cools and solidifies. Sedimentary rocks form from layers of sediment compressed over millions of years and often contain fossils. Metamorphic rocks form when existing rocks are changed by heat and pressure.
岩石分为三大类。火成岩由岩浆或熔岩冷却凝固形成。沉积岩由沉积物经过数百万年压实成层而形成，常含有化石。变质岩是原有岩石受热和压力作用变质而成。
The Solar System consists of the Sun, eight planets, their moons, and smaller objects like asteroids and comets. The Sun is a star, and its gravity keeps the planets in orbit. Earth orbits the Sun once every 365.25 days, causing the cycle of seasons.
太阳系由太阳、八大行星、它们的卫星以及小行星和彗星等小天体组成。太阳是一颗恒星，它的引力使行星保持在轨道上。地球每 365.25 天绕太阳公转一周，形成四季循环。
The Moon orbits Earth roughly every 28 days. We see phases of the Moon because the illuminated half changes as the Moon moves. Eclipses occur when the Earth blocks sunlight to the Moon (lunar eclipse) or the Moon blocks sunlight to a part of Earth (solar eclipse).
月球大约每 28 天绕地球一周。我们看到的月相变化是因为月球运动时被照亮的一面不断变化。当地球挡住射向月球的阳光时发生月食，当月球挡住射向地球某一部分的阳光时发生日食。
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