📚 Activate 2 Science Revision Guide | Activate 2 科学复习指南
This guide covers the core ideas from Oxford Activate 2 for KS3 science. It brings together key concepts from biology, chemistry and physics, including health, ecosystems, the periodic table, reactions, energy, electricity and motion. Each section gives a concise revision point followed by its Chinese translation.
本指南涵盖牛津 Activate 2 初中科学的核心内容。它汇集了生物学、化学和物理的关键概念，包括健康、生态系统、元素周期表、化学反应、能量、电学以及运动。每节先给出简洁的复习要点，再附中文翻译。
1. Health and Lifestyle | 健康与生活方式
A balanced diet provides carbohydrates, proteins, lipids, vitamins, minerals, water and fibre. Each nutrient has a specific role: carbohydrates release energy, proteins support growth and repair, lipids store energy and insulate organs, while vitamins and minerals keep body processes working normally.
均衡饮食提供碳水化合物、蛋白质、脂类、维生素、矿物质、水和膳食纤维。每种营养素都有特定作用：碳水化合物释放能量，蛋白质支持生长和修复，脂类储存能量并保护器官，而维生素和矿物质维持身体正常的生理过程。
Digestion involves mechanical breakdown and enzyme action. Amylase breaks down starch into sugars, protease breaks down proteins into amino acids, and lipase breaks down lipids into fatty acids and glycerol. The small intestine absorbs these small molecules into the blood.
消化包括物理分解和酶的作用。淀粉酶将淀粉分解为糖，蛋白酶将蛋白质分解为氨基酸，脂肪酶将脂类分解为脂肪酸和甘油。小肠把这些小分子吸收进入血液。
Lifestyle choices affect health. Regular exercise strengthens the heart and lungs, while smoking damages the airways and increases the risk of lung cancer. Excess alcohol can harm the liver and brain, and drugs may alter mood, behaviour or body chemistry.
生活方式的选择会影响健康。经常锻炼可以增强心脏和肺，而吸烟会损伤气道并增加肺癌风险。过量饮酒会损害肝脏和大脑，药物则可能改变情绪、行为或身体的化学状态。
2. Ecosystem Processes | 生态系统过程
+ water → glucose + oxygen. It occurs in chloroplasts and requires chlorophyll and light.
光合作用是绿色植物利用光能制造葡萄糖的过程。文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气。该过程发生在叶绿体中，需要叶绿素和光照。
on dioxide + water. This energy is used for movement, growth, repair and maintaining body temperature.
有氧呼吸在活细胞中从葡萄糖释放能量。文字方程式为：葡萄糖 + 氧气 → 二氧化碳 + 水。这些能量用于运动、生长、修复和维持体温。
Food chains show the transfer of energy and matter between organisms. Producers make their own food, primary consumers eat producers, and secondary consumers eat primary consumers. Decomposers such as bacteria and fungi break down dead material and return nutrients to the soil.
食物链显示生物之间能量和物质的传递。生产者自己制造食物，初级消费者吃生产者，次级消费者吃初级消费者。细菌和真菌等分解者分解死亡物质并将养分归还土壤。
3. Adaptation and Inheritance | 适应与遗传
An adaptation is a feature that helps an organism survive and reproduce in its environment. Examples include thick fur in Arctic animals, large ears in desert foxes for heat loss, and streamlined bodies in fish.
适应性是指帮助生物在环境中生存和繁殖的特征。例如北极动物的厚毛、沙漠狐用于散热的大耳朵以及鱼类的流线型身体。
Natural selection explains how species change over time. Individuals with advantageous traits are more likely to survive and pass these traits to their offspring. Over many generations, the favourable traits become more common in the population.
自然选择解释物种如何随时间变化。具有有利特征的个体更可能生存并将这些特征传给后代。经过许多代之后，有利的特征在种群中会变得更加普遍。
Genes located on chromosomes carry inherited characteristics. Variation within a species arises from differences in genes and from environmental factors. Some variation is continuous, such as height, while some is discontinuous, such as blood group.
位于染色体上的基因携带遗传特征。物种内的变异来自基因差异和环境因素。有些变异是连续的，例如身高；有些则是不连续的，例如血型。
4. The Periodic Table | 元素周期表
The periodic table arranges elements in order of atomic number. Rows are periods and columns are groups. Elements in the same group have similar chemical properties because they have the same number of outer electrons.
元素周期表按原子序数递增的顺序排列元素。横行为周期，纵列为族。同一族元素因最外层电子数相同而具有相似的化学性质。
Metals are typically shiny, good conductors of heat and electricity, malleable and ductile. Non-metals are often dull, poor conductors, and brittle when solid. Group 1 contains reactive alkali metals, Group 7 contains halogens, and Group 0 contains noble gases.
金属通常有光泽，是热和电的良导体，具有延展性。非金属通常暗淡、导电性差，固体状态下易碎。第1族是活泼的碱金属，第7族是卤素，第0族是稀有气体。
Elements are made of only one type of atom, while compounds contain two or more elements chemically joined. A chemical formula shows the atoms present, such as H₂O for water and CO₂ for carbon dioxide.
元素只由一种原子组成，而化合物含有两种或多种化学结合的元素。化学式表示所含的原子，例如 H₂O 表示水，CO₂ 表示二氧化碳。
5. Separation Techniques | 分离技术
Mixtures can be separated by physical methods. Filtration separates an insoluble solid from a liquid; evaporation separates a dissolved solid from a solution by boiling off the solvent; distillation separates a solvent from a solution and collects it by condensation.
混合物可以用物理方法分离。过滤将不溶性固体与液体分离；蒸发通过蒸发溶剂从溶液中分离可溶固体；蒸馏将溶剂从溶液中分离并通过冷凝收集。
Chromatography separates dissolved substances based on their different solubilities and attraction to the paper. The mixture moves with the solvent and produces a chromatogram, which can be compared with known dyes or inks.
色谱法利用溶解物质在溶剂中的溶解度和对滤纸的吸附力不同进行分离。混合物随溶剂移动并形成色谱图，可以与已知染料或墨水进行对比。
Magnetic separation can remove magnetic materials from a mixture. For example, a magnet can attract iron filings away from sand. Choosing a separation method depends on the physical properties of the substances in the mixture.
磁分离可以从混合物中除去磁性材料。例如，磁铁可以把铁屑从沙子中吸出。选择分离方法取决于混合物中各物质的物理性质。
6. Metals and Acids | 金属与酸
lt + hydrogen. For example, hydrochloric acid + magnesium → magnesium chloride + hydrogen.
酸能与许多金属反应生成盐和氢气。一般文字方程式为：酸 + 金属 → 盐 + 氢气。例如：盐酸 + 镁 → 氯化镁 + 氢气。
The reactivity series lists metals from most reactive to least reactive: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, copper, gold. More reactive metals react faster with acids and can displace less reactive metals from solutions.
金属活动性顺序从强到弱排列：钾、钠、钙、镁、铝、锌、铁、铅、铜、金。较活泼的金属与酸反应更快，并能从溶液中置换较不活泼的金属。
+ alkali → salt + water. This reaction is useful in treating acidic soil and indigestion.
中和反应是酸与碱反应生成盐和水的过程。一般方程式为：酸 + 碱 → 盐 + 水。该反应可用于改良酸性土壤和缓解消化不良。
7. The Earth and Atmosphere | 地球与大气
The Earth is made of layers: crust, mantle, outer core and inner core. Rocks are classified into igneous, sedimentary and metamorphic types, and they change through the rock cycle over millions of years.
地球由多层构成：地壳、地幔、外核和内核。岩石分为火成岩、沉积岩和变质岩，并在数百万年间通过岩石循环相互转化。
The atmosphere is mainly nitrogen (about 78%) and oxygen (about 21%), with small amounts of argon, carbon dioxide and water vapour. Carbon cycles through photosynthesis, respiration, combustion and decomposition.
大气主要由氮气（约78%）和氧气（约21%）组成，还有少量氩气、二氧化碳和水蒸气。碳通过光合作用、呼吸作用、燃烧和分解进行循环。
Fossils provide evidence for evolution and changes in the environment. They form when remains or traces of organisms are buried and preserved in sedimentary rock. Studying rock layers helps scientists understand the history of the Earth.
化石为进化以及环境变化提供证据。当生物遗体或痕迹被埋藏并保存在沉积岩中时就形成化石。研究岩层有助于科学家了解地球的历史。
8. Electricity and Magnetism | 电与磁
Electric current is the flow of electric charge. A series circuit has only one loop, so the current is the same everywhere. A parallel circuit has more than one loop, and the current splits while the voltage remains the same across each branch.
电流是电荷的流动。串联电路只有一个回路，因此各处电流相同。并联电路有多个回路，电流会分流，但各支路两端的电压相同。
Resistance measures how difficult it is for current to flow. Wires, bulbs and resistors have resistance. Adding more bulbs in series increases total resistance and reduces the current in the circuit.
电阻衡量电流通过的难易程度。导线、灯泡和电阻器都有电阻。在串联电路中增加更多灯泡会增加总电阻并减小电路中的电流。
An electromagnet is made by wrapping a wire coil around an iron core; it becomes magnetic when current flows. The strength can be increased by adding more coils, increasing the current, or using a soft iron core.
电磁铁由绕在铁芯上的线圈制成，通电后具有磁性。增加线圈匝数、增大电流或使用软铁芯都可以增强磁性。
9. Energy Stores and Transfers | 能量储存与转移
Energy can be stored as kinetic, gravitational potential, chemical, elastic, thermal, nuclear and magnetic energy. Energy cannot be created or destroyed; it is conserved and transferred between stores.
能量可以储存为动能、重力势能、化学能、弹性势能、热能、核能和磁能。能量既不能凭空产生，也不会凭空消失；能量守恒并在不同储存形式之间转移。
y power = energy transferred ÷ time. The unit of power is the watt (W), where 1 W = 1 J/s.
功率是能量转移的速率。计算公式为：功率 = 转移的能量 ÷ 时间。功率的单位是瓦特（W），1 W = 1 J/s。
Energy transfers can be shown using Sankey diagrams. Useful energy is transferred to where it is wanted, but some energy is always wasted, often as heat. Efficiency compares useful output energy with total input energy.
能量转移可以用桑基图表示。有用能量被转移至需要的地方，但总有一部分能量被浪费，通常以热的形式散失。效率是比较有用输出能量与总输入能量。
10. Motion and Pressure | 运动与压强
e. It is calculated by speed = distance ÷ time. Average speed can be found from a distance–time graph, where a steeper line means higher speed.
速度是单位时间内通过的距离。计算公式为：速度 = 距离 ÷ 时间。平均速度可以从路程-时间图中得出，线越陡表示速度越快。
ntrates force and gives high pressure, as seen with sharp blades; a large area spreads force and lowers pressure, as seen with snowshoes.
压强是单位面积上的压力。压强 = 力 ÷ 面积。面积小会使力集中从而产生较大压强，如锋利的刀刃；面积大会分散力从而减小压强，如雪鞋。
Pressure in fluids increases with depth and acts in all directions. This explains why dams are thicker at the bottom and why submarines need strong walls to withstand high pressure deep underwater.
流体中的压强随深度增加，并且向各个方向作用。这解释了为什么水坝底部更厚，以及为什么潜艇需要坚固的舱壁来承受深水下的高压。
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