📚 Year 7 CIE Science: Core Knowledge Review | Year 7 CIE 科学：核心知识点梳理
This comprehensive revision guide covers the essential topics for Year 7 CIE Science. It summarises key concepts in biology, chemistry, and physics to help you build a solid foundation for Checkpoint and beyond.
这份综合复习指南涵盖 Year 7 CIE 科学的核心主题。它总结了生物学、化学和物理学的关键概念，帮助你在 Checkpoint 及以后的学习中打下坚实基础。
1. Cells – The Building Blocks of Life | 细胞——生命的基石
All living things are made of cells. Cells are the basic units of life that carry out all life processes such as respiration, growth, and reproduction.
所有生物都由细胞构成。细胞是进行一切生命活动（如呼吸、生长和繁殖）的基本单位。
Most cells contain a cell membrane, cytoplasm, and a nucleus that controls activities. Mitochondria release energy through respiration. Plant cells have extra structures: a rigid cell wall made of cellulose, chloroplasts for photosynthesis, and a large permanent vacuole filled with cell sap.
大多数细胞含有细胞膜、细胞质和控制生命活动的细胞核。线粒体通过呼吸作用释放能量。植物细胞具有额外的结构：由纤维素构成的坚硬细胞壁、进行光合作用的叶绿体，以及充满细胞液的大液泡。
| Feature | Animal Cell | Plant Cell |
|---|---|---|
| Cell wall | Absent | Present (cellulose) |
| Chloroplasts | Absent | Present |
| Vacuole | Small temporary vacuoles | Large central vacuole |
The table above highlights the main differences: plant cells possess a cell wall, chloroplasts, and a large vacuole, whereas animal cells do not.
上表突出了主要区别：植物细胞具有细胞壁、叶绿体和大液泡，而动物细胞没有这些结构。
Many cells are specialised to perform specific functions. For example, red blood cells are biconcave discs that carry oxygen, root hair cells have long projections to absorb water and minerals, and sperm cells have a tail to swim.
许多细胞特化以行使特定功能。例如，红细胞是携带氧气的双凹圆盘状，根毛细胞有细长突起以吸收水分和矿物质，精子细胞有尾巴用于游动。
Groups of similar cells form tissues, tissues form organs, and organs work together in organ systems.
相似细胞组成组织，组织构成器官，器官协同工作形成器官系统。
2. Classification of Living Organisms | 生物的分类
Biologists classify living things based on shared features. The five-kingdom system divides life into Animals, Plants, Fungi, Protists, and Monera (bacteria). Members of each kingdom share fundamental characteristics.
生物学家根据共同特征对生物进行分类。五界系统将生物分为动物界、植物界、真菌界、原生生物界和原核生物界（细菌）。每个界内的成员具有基本的共同特征。
Animals are further grouped into vertebrates (with a backbone) and invertebrates (without). Vertebrates include five main classes: mammals, birds, fish, reptiles, and amphibians. Each class has defining traits—mammals have fur and produce milk, birds have feathers and lay hard-shelled eggs, fish breathe with gills, reptiles have dry scaly skin, and amphibians have moist skin and live both in water and on land.
动物可进一步分为脊椎动物（有脊柱）和无脊椎动物（没有脊柱）。脊椎动物包括五个主要类别：哺乳动物、鸟类、鱼类、爬行动物和两栖动物。每一类都有典型特征——哺乳动物有皮毛并产奶，鸟类有羽毛并产硬壳蛋，鱼类用鳃呼吸，爬行动物皮肤干燥有鳞片，两栖动物皮肤湿润且水陆两栖。
Plants are mainly classified as flowering plants (which reproduce using seeds inside fruits) and non-flowering plants such as mosses and ferns, which use spores for reproduction.
植物主要分为开花植物（通过果实内的种子繁殖）和非开花植物（如苔藓和蕨类，用孢子繁殖）。
3. States of Matter and the Particle Model | 物质状态与粒子模型
All matter exists in one of three states: solid, liquid, or gas. The particle model helps explain the properties of each state in terms of the arrangement and movement of tiny particles.
所有物质以三种状态之一存在：固态、液态或气态。粒子模型通过微小粒子的排列和运动来解释每种状态的性质。
In a solid, particles are tightly packed in a regular pattern and can only vibrate in fixed positions. Solids have a definite shape and cannot flow.
在固态中，粒子紧密排列成规则图案，只能在固定位置振动。固体有确定的形状，不能流动。
In a liquid, particles are still close together but are not in a fixed arrangement. They can move past each other, allowing liquids to flow and take the shape of their container.
在液态中，粒子依然彼此靠近但排列不规则。它们可以相互滑动，使得液体能够流动并呈现容器的形状。
In a gas, 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，粒子相距很远并向各个方向快速运动。气体没有固定的形状或体积，且容易被压缩。
Changes of state—such as melting, freezing, boiling, and condensation—occur when a substance gains or loses energy, altering how its particles behave.
状态变化——如熔化、凝固、沸腾和凝结——发生在物质获得或失去能量时，粒子的行为随之改变。
4. Atoms, Elements, and Compounds | 原子、元素与化合物
All substances are made of tiny particles called atoms. An element is a pure substance that contains only one type of atom. Each element is represented by a unique chemical symbol, for example O for oxygen and Fe for iron.
所有物质由微粒——原子构成。元素是只含有一种原子的纯净物。每种元素用独特的化学符号表示，例如 O 代表氧，Fe 代表铁。
The Periodic Table organises all known elements in order of increasing atomic number. Elements in the same group have similar chemical properties.
元素周期表按原子序数递增的顺序排列所有已知元素。同一族中的元素具有相似的化学性质。
A compound forms when two or more different elements chemically combine in fixed proportions. Compounds have properties that are often very different from the elements they contain. For example, water (H₂O) is a liquid compound of hydrogen and oxygen, whereas hydrogen is a flammable gas and oxygen supports combustion.
当两种或多种不同元素以固定比例通过化学方式结合时，就会形成化合物。化合物的性质通常与组成它的元素截然不同。例如，水 (H₂O) 是氢和氧的液态化合物，而氢气是可燃气体，氧气助燃。
We represent compounds using
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