📚 Year 7 WJEC Science: Core Knowledge Points Review | Year 7 WJEC 科学：核心知识点梳理
Welcome to your comprehensive revision guide for Year 7 WJEC Science. This article summarises the essential knowledge you need across biology, chemistry and physics, with clear explanations and helpful tables.
欢迎阅读 Year 7 WJEC 科学综合复习指南。本文总结了生物、化学和物理三个学科的核心知识点，提供清晰的解释和实用的表格。
1. Cells – The Building Blocks of Life | 细胞——生命的基石
All living organisms are made up of cells. Cells are the smallest units of life and can only be seen under a microscope.
所有生物体都由细胞构成。细胞是生命的最小单位，只能在显微镜下观察到。
Animal cells have a nucleus, cytoplasm, cell membrane and mitochondria. Plant cells have all of these plus a rigid cell wall, a large central vacuole and chloroplasts for photosynthesis.
动物细胞具有细胞核、细胞质、细胞膜和线粒体。植物细胞除了这些结构，还有坚硬的细胞壁、中央大液泡和用于光合作用的叶绿体。
- Nucleus – controls cell activities (细胞核——控制细胞活动)
- Cytoplasm – jelly-like substance where reactions occur (细胞质——进行反应的胶状物质)
- Cell membrane – controls what enters and leaves (细胞膜——控制物质进出)
- Mitochondria – release energy through respiration (线粒体——通过呼吸作用释放能量)
- Cell wall (plants) – provides support (细胞壁——提供支持)
- Chloroplasts (plants) – contain chlorophyll for photosynthesis (叶绿体——含有叶绿素进行光合作用)
- Vacuole (plants) – stores sap and helps with rigidity (液泡——储存细胞液，帮助保持坚挺)
Specialised cells are adapted to do a particular job. For example, red blood cells have no nucleus to carry more oxygen, and root hair cells have a large surface area to absorb water.
特化细胞适应执行特定功能。例如，红细胞没有细胞核以便携带更多氧气，根毛细胞具有较大的表面积来吸收水分。
2. States of Matter | 物质的状态
Everything around us is made of matter, which exists in three main states: solid, liquid and gas. These states have different properties depending on how the particles are arranged and move.
我们周围的一切都是由物质构成的，物质以三种主要状态存在：固态、液态和气态。这些状态的性质取决于粒子的排列方式和运动方式。
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Particle arrangement | Tightly packed, regular pattern | Close together, random | Far apart, random |
| Movement | Vibrate in fixed positions | Move around each other | Move quickly in all directions |
| Shape | Fixed | Takes shape of container | Fills container |
| Volume | Fixed | Fixed | Not fixed |
Changes of state, such as melting and boiling, occur when energy is added or removed. Melting is when a solid becomes a liquid, and boiling is when a liquid turns into a gas.
状态的变化，如熔化和沸腾，发生在加入或移除能量时。熔化是固态变为液态，沸腾是液态变为气态。
The particle model can explain why solids hold their shape, liquids can flow, and gases spread out to fill a container.
粒子模型可以解释为什么固体保持形状、液体能够流动、气体会扩散并充满容器。
3. Forces and Motion | 力与运动
A force is a push or a pull. Forces are measured in newtons (N). They can change the speed, direction or shape of an object.
力是推或拉。力的单位是牛顿（N）。力可以改变物体的速度、方向或形状。
Contact forces require objects to touch, such as friction and air resistance. Non-contact forces act over a distance, like gravity and magnetism.
接触力需要物体相互接触，例如摩擦力和空气阻力。非接触力在一定距离外起作用，如重力和磁力。
Weight (N) = mass (kg) × gravitational field strength (N/kg)
On Earth, the gravitational field strength is approximately 10 N/kg. This means a 1 kg object weighs 10 N.
地球上的引力场强度约为10 N/kg。这意味着一个1 kg的物体重量为10 N。
Balanced forces mean no change in motion; an object stays still or moves at a constant speed. Unbalanced forces cause acceleration or deceleration.
平衡力意味着运动状态不变；物体保持静止或匀速运动。非平衡力导致加速或减速。
4. Energy Stores and Transfers | 能量的储存与转移
Energy cannot be created or destroyed, only transferred or stored. Common energy stores include kinetic, thermal, chemical, gravitational potential and elastic potential energy.
能量不能被创造或消灭，只能被转移或储存。常见的能量储存包括动能、热能、化学能、重力势能和弹性势能。
Energy can be transferred by heating, waves, electric current, or mechanically (by forces). Sankey diagrams show energy transfers, with the arrow thickness indicating the amount of energy.
能量可以通过加热、波、电流或机械（力）的方式转移。桑基图展示能量转移，箭头的粗细表示能量的大小。
Efficiency = (Useful output energy ÷ Total input energy) × 100%
A filament light bulb is inefficient because most of the input energy is transferred as thermal energy, not light. An LED is much more efficient.
白炽灯效率低，因为大部分输入能量转化为热能而非光。LED灯效率则高得多。
5. Reproduction in Plants | 植物的繁殖
Flowering plants reproduce sexually. The male sex cell (pollen) must fertilise the female sex cell (ovule). Pollination is the transfer of pollen from the anther to the stigma.
开花植物通过有性繁殖产生后代。雄性生殖细胞（花粉）必须受精雌性生殖细胞（胚珠）。传粉是花粉从花药转移到柱头的过程。
Wind-pollinated plants have light, smooth pollen and small, dull flowers. Insect-pollinated plants have bright petals, scent and sticky pollen.
风媒传粉植物的花粉轻而光滑，花朵小且颜色暗淡。虫媒传粉植物花瓣鲜艳、有香味，花粉具有黏性。
After fertilisation, the ovule becomes a seed and the ovary develops into a fruit. Seed dispersal can be by wind, water, animals or explosion.
受精后，胚珠发育成种子，子房发育成果实。种子可以通过风、水、动物或爆炸的方式传播。
6. Acids and Alkalis | 酸与碱
Substances can be acidic, alkaline or neutral. The pH scale measures this, ranging from 0 (strong acid) to 14 (strong alkali). A pH of 7 is neutral, like pure water.
物质可以是酸性、碱性或中性。pH 值标度衡量酸碱度，范围从0（强酸）到14（强碱）。pH 7 为中性，例如纯水。
Acids contain hydrogen ions (H⁺) when dissolved in water. Alkalis contain hydroxide ions (OH⁻). Indicators like litmus and universal indicator change colour to show pH.
酸溶于水时含有氢离子（H⁺），碱含有氢氧根离子（OH⁻）。石蕊和通用指示剂等指示剂能通过颜色变化显示 pH 值。
Neutralisation is a reaction between an acid and an alkali, producing a salt and water. This is an important reaction used in farming and medicine.
中和反应是酸和碱之间的反应，生成盐和水。这是一个在农业和医学中十分重要的反应。
HCl + NaOH → NaCl + H₂O
7. The Solar System | 太阳系
Our Solar System consists of the Sun, eight planets, their moons, dwarf planets, asteroids and comets. The Sun is a star at the centre, providing light and heat.
我们的太阳系由太阳、八颗行星、它们的卫星、矮行星、小行星和彗星组成。太阳是中心的恒星，提供光和热。
The inner planets (Mercury, Venus, Earth, Mars) are rocky. The outer planets (Jupiter, Saturn, Uranus, Neptune) are gas giants. The asteroid belt lies between Mars and Jupiter.
内行星（水星、金星、地球、火星）是岩石行星。外行星（木星、土星、天王星、海王星）是气态巨行星。小行星带位于火星和木星之间。
The Earth's rotation on its axis causes day and night. Its orbit around the Sun takes one year (365¼ days) and causes the seasons.
地球绕轴自转导致了昼夜交替。地球绕太阳公转一周需要一年（365¼天），并产生了四季变化。
8. Variation and Classification | 变异与分类
Variation is the differences between living organisms. Continuous variation (e.g. height) shows a range of values. Discontinuous variation (e.g. eye colour) falls into distinct groups.
变异是生物体之间的差异。连续变异（如身高）呈现一系列数值。不连续变异（如眼睛颜色）分为明确的类别。
Scientists classify organisms into groups based on shared features. The five kingdoms are Animals, Plants, Fungi, Protists and Prokaryotes.
科学家根据共同特征将生物分类。五个界分别是动物界、植物界、真菌界、原生生物界和原核生物界。
Within each kingdom, organisms are further sorted into phylum, class, order, family, genus and species. The binomial naming system uses genus and species names.
在每个界内，生物进一步被分为门、纲、目、科、属和种。双名法使用属名和种名进行命名。
9. Chemical Reactions | 化学反应
A chemical reaction involves the formation of new substances. Signs include colour change, temperature change, gas production or formation of a precipitate.
化学反应涉及新物质的生成。迹象包括颜色变化、温度变化、产生气体或形成沉淀。
In a chemical reaction, reactants are rearranged to form products. The total mass stays the same – this is the law of conservation of mass.
在化学反应中，反应物重组生成产物。总质量保持不变——这就是质量守恒定律。
Simple reactions you need to know include combustion (burning fuels), oxidation (rusting of iron), and thermal decomposition (breaking down by heat).
你需要了解的简单反应包括燃烧（燃料燃烧）、氧化（铁生锈）和热分解（受热分解）。
2Mg + O₂ → 2MgO
Magnesium burns in oxygen to form magnesium oxide, a white powder. This is a synthesis reaction.
镁在氧气中燃烧生成氧化镁，一种白色粉末。这是一个化合反应。
10. Electricity | 电
An electric current is the flow of electric charge, usually electrons, around a circuit. A complete circuit is needed for current to flow.
电流是电荷（通常是电子）在电路中的流动。需要完整的电路才能有电流通过。
Circuit symbols represent components like cells, batteries, bulbs, switches and motors. You must be able to draw and interpret circuit diagrams.
电路符号代表电池组、电池、灯泡、开关和马达等元件。你必须能够绘制和解读电路图。
Potential difference (V) = Current (A) × Resistance (Ω)
Ohm's law is fundamental: increasing resistance reduces the current if the voltage is constant. Conductors have low resistance; insulators have very high resistance.
欧姆定律是基础：若电压不变，电阻增大会使电流减小。导体的电阻低，绝缘体的电阻非常高。
Series circuits have only one path; current is the same everywhere. Parallel circuits have multiple branches; the total current is shared.
串联电路只有一条路径，各处电流相同。并联电路有多条支路，总电流被分流。
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