Core Concepts in SQA Science | SQA科学核心知识点梳理

📚 Core Concepts in SQA Science | SQA科学核心知识点梳理

SQA National 5 Science covers a broad range of topics across biology, chemistry and physics, building on the foundations laid in earlier years. This article brings together the essential knowledge you need to master for your assessments – from how science works to the key ideas in each discipline. Each section pairs an English explanation with its Chinese counterpart to support bilingual learning.

SQA国家5级科学课程涵盖生物、化学和物理的广泛主题，是在早期基础上进一步深化。本文汇整了考试评估中必须掌握的核心知识——从科学工作方法到各学科的关键概念。每个小节都配有英文和中文对照说明，助力双语学习。

1. Scientific Inquiry and Variables | 科学探究与变量

All scientific investigations begin with a question. You then design a fair test to collect reliable data. The independent variable is the one you change; the dependent variable is what you measure; all other variables must be kept constant to avoid affecting the results.

所有科学探究都始于一个问题。你需要设计一个公平的实验来收集可靠的数据。自变量是你改变的量；因变量是你测量的量；所有其他变量必须保持不变，以免影响结果。

Repeating measurements and calculating a mean helps to improve accuracy and identify any anomalous results. A valid conclusion must be supported by the evidence and refer back to the aim of the experiment.

重复测量并计算平均值有助于提高准确度，并识别异常结果。有效的结论必须得到证据的支持，并紧扣实验目的。

Independent variable – plotted on the x-axis of a graph.
Dependent variable – plotted on the y-axis.
Control variables – factors kept the same to ensure a fair test.

自变量 – 绘制在图表的x轴上。
因变量 – 绘制在y轴上。
控制变量 – 保持不变的因素，以确保公平实验。

2. Cells and DNA | 细胞与DNA

The cell is the basic unit of life. Animal and plant cells both have a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells also possess a rigid cell wall, a permanent vacuole and chloroplasts for photosynthesis.

细胞是生命的基本单位。动植物细胞都具有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还拥有坚硬的细胞壁、一个永久液泡以及进行光合作用的叶绿体。

DNA is a double‑stranded helix that carries genetic instructions. It is made from four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). A always pairs with T, and C with G. Genes are sections of DNA that code for specific proteins.

DNA是携带遗传指令的双链螺旋结构。它由四种碱基构成：腺嘌呤(A)、胸腺嘧啶(T)、胞嘧啶(C)和鸟嘌呤(G)。A始终与T配对，C与G配对。基因是编码特定蛋白质的DNA片段。

Organelle	Function
Nucleus	Controls cell activities / contains DNA
Mitochondria	Site of aerobic respiration
Ribosomes	Protein synthesis
Chloroplasts (plant only)	Absorb light for photosynthesis

细胞器	功能
细胞核	控制细胞活动 / 含有DNA
线粒体	有氧呼吸的场所
核糖体	蛋白质合成
叶绿体（仅植物）	吸收光能进行光合作用

3. Photosynthesis and Respiration | 光合作用与呼吸

Photosynthesis uses light energy to convert carbon dioxide and water into glucose and oxygen. The overall word equation is:

光合作用利用光能将二氧化碳和水转化为葡萄糖和氧气。总的文字方程式为：

carbon dioxide + water → glucose + oxygen

二氧化碳 + 水 → 葡萄糖 + 氧气

Light intensity, carbon dioxide concentration and temperature all affect the rate of photosynthesis. Limiting factors can be identified from the plateau of a graph.

光照强度、二氧化碳浓度和温度都会影响光合作用的速率。限制因素可以通过曲线图的平台区域来识别。

Aerobic respiration releases energy from glucose using oxygen. It takes place in mitochondria and can be summarised as:

有氧呼吸利用氧气从葡萄糖中释放能量。它发生在线粒体中，可概括为：

glucose + oxygen → carbon dioxide + water (+ energy)

葡萄糖 + 氧气 → 二氧化碳 + 水 (+ 能量)

During vigorous exercise, if oxygen supply is insufficient, muscle cells switch to anaerobic respiration, producing lactic acid and less energy. In yeast, anaerobic respiration produces ethanol and carbon dioxide – a process called fermentation.

剧烈运动时，如果氧气供应不足，肌细胞会转为无氧呼吸，产生乳酸和较少的能量。在酵母中，无氧呼吸产生乙醇和二氧化碳，这一过程称为发酵。

4. Atoms, Elements and Compounds | 原子、元素与化合物

All substances are made of atoms. An element contains only one type of atom, while a compound contains two or more different types chemically bonded together. The periodic table lists all known elements.

所有物质都由原子构成。元素仅包含一种原子，而化合物包含两种或以上不同原子以化学键结合。元素周期表列出了所有已知元素。

Atoms consist of a central nucleus (protons and neutrons) surrounded by electrons in energy levels. The atomic number tells you the number of protons; the mass number is the total of protons plus neutrons.

原子由中心原子核（质子和中子）以及处于能级上的电子组成。原子序数表示质子数；质量数是质子数加中子数的总和。

Particle	Charge	Mass (relative)
Proton	+1	1
Neutron	0	1
Electron	-1	~0

粒子	电荷	相对质量
质子	+1	1
中子	0	1
电子	-1	≈0

Chemical formulae show the ratio of atoms in a compound, e.g. H₂O has two hydrogen atoms for every oxygen atom. Chemical equations must be balanced to conserve mass.

化学式表示化合物中原子的比例，例如H₂O表示每有一个氧原子就有两个氢原子。化学方程式必须配平以体现质量守恒。

5. The Periodic Table and Bonding | 周期表与化学键

The periodic table is arranged in order of increasing atomic number. Groups are vertical columns; 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。族是纵向列；同族元素具有相似的化学性质，因为它们的最外层电子数相同。

Group 1 – alkali metals – are very reactive, especially with water. Group 7 – halogens – are reactive non‑metals. Group 8/0 – noble gases – are unreactive because their outer shells are full.

第1族——碱金属——非常活泼，特别是与水反应。第7族——卤素——是活泼的非金属。第8/0族——稀有气体——不活泼，因为它们的最外电子层已满。

Atoms bond to achieve a stable electron arrangement. Ionic bonding occurs between a metal and a non‑metal: electrons are transferred, forming positive and negative ions that attract. Covalent bonding happens between non‑metals: atoms share pairs of electrons to fill their outer shells.

原子通过成键获得稳定的电子排布。离子键形成于金属和非金属之间：电子转移，形成相互吸引的正负离子。共价键发生在非金属之间：原子共享电子对来填满最外层。

Ionic compounds: high melting/boiling points, conduct electricity when molten/dissolved.
Covalent molecular substances: low melting/boiling points, often do not conduct electricity.

离子化合物：熔点/沸点高，熔融或溶解时导电。
共价分子物质：熔点/沸点低，通常不导电。

6. Acids, Alkalis and Neutralisation | 酸、碱与中和反应

Acids release hydrogen ions (H⁺) in water, while alkalis release hydroxide ions (OH⁻). The pH scale runs from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral.

酸在水中释放氢离子（H⁺），而碱释放氢氧根离子（OH⁻）。pH标度从0（强酸）到14（强碱），7为中性。

Neutralisation is the reaction between an acid and a base (or alkali) producing a salt and water. The general equation is:

中和反应是酸与碱（或碱性物质）反应生成盐和水的过程。通式为：

acid + base → salt + water

酸 + 碱 → 盐 + 水

The name of the salt comes from the acid used: hydrochloric acid produces chlorides, sulfuric acid produces sulfates, nitric acid produces nitrates. Metal oxides and metal carbonates also neutralise acids – a carbonate reaction produces salt, water and carbon dioxide.

盐的名称来自所用的酸：盐酸产生氯化物，硫酸产生硫酸盐，硝酸产生硝酸盐。金属氧化物和金属碳酸盐也能中和酸——碳酸盐反应生成盐、水和二氧化碳。

Titration is a practical technique used to find the exact volume of acid needed to neutralise a known volume of alkali, using an indicator to signal the end point.

滴定是一种实用技术，用于确定中和一定体积碱液所需酸的精确体积，通过指示剂显示终点。

7. Forces and Motion | 力与运动

Forces can change the speed, direction or shape of an object. When forces are balanced, an object remains at rest or moves at a constant speed in a straight line. Unbalanced forces cause acceleration.

力可以改变物体的速度、方向或形状。力平衡时，物体保持静止或沿直线匀速运动。不平衡的力会导致加速。

Key quantities and relationships:

关键物理量及其关系：

average speed = distance ÷ time

平均速率 = 路程 ÷ 时间

acceleration = change in velocity ÷ time taken

加速度 = 速度变化量 ÷ 所花时间

force = mass × acceleration (F = ma)

力 = 质量 × 加速度 (F = ma)

weight = mass × gravitational field strength (W = mg, g = 9.8 N/kg on Earth)

重量 = 质量 × 重力场强度 (W = mg, 地球上g = 9.8 N/kg)

Velocity–time graphs and distance–time graphs provide a visual way to analyse motion. The slope of a distance–time graph gives speed; the slope of a velocity–time graph gives acceleration, and the area under the line represents displacement.

速度–时间图和距离–时间图提供了分析运动的可视化方法。距离–时间图的斜率表示速率；速度–时间图的斜率表示加速度，图线下的面积代表位移。

8. Energy Forms and Transfers | 能量形式与传递

Energy exists in different forms: kinetic, gravitational potential, chemical, thermal (heat), electrical, light, sound and nuclear. Energy can be transferred from one store to another, but the total energy is always conserved.

能量以不同形式存在：动能、重力势能、化学能、热能、电能、光能、声能和核能。能量可以从一种储存形式转移到另一种，但总能量始终守恒。

Work done is a measure of energy transferred. The work done by a force is calculated as:

做功是能量传递的度量。一个力所做的功计算如下：

work done = force × distance moved in direction of force (Ew = Fd)

做功 = 力 × 沿力方向移动的距离 (Ew = Fd)

Gravitational potential energy gained by lifting an object is:

举起物体获得的重力势能为：

Ep = mgh

重力势能 Ep = mgh

Kinetic energy of a moving object is:

运动物体的动能为：

Ek = ½ mv²

动能 Ek = ½ mv²

In many processes, energy is dissipated – spread out as heat to the surroundings – making it less useful. Efficiency is the ratio of useful output energy to total input energy, often expressed as a percentage.

在许多过程中，能量会耗散——以热的形式散失到周围环境——从而降低其实用性。效率是有用输出能量与总输入能量之比，通常以百分比表示。

9. Electricity and Circuits | 电与电路

Electric current is the flow of charge. In a complete circuit, current (I, in amperes) passes from the positive terminal to the negative terminal (conventional direction). Voltage (potential difference, V) provides the push that drives the current.

电流是电荷的流动。在闭合电路中，电流（I，单位为安培）从正极流向负极（常规方向）。电压（电势差，V）提供驱动电流的推力。

Resistance (R) opposes the flow of current. Ohm’s law relates these quantities:

电阻（R）阻碍电流流动。欧姆定律关联这些物理量：

V = I × R

电压 = 电流 × 电阻

Type of circuit	Current	Voltage
Series	Same everywhere	Shared across components
Parallel	Splits at branches	Same across each branch

电路类型	电流	电压
串联	各处相同	各元件分担
并联	支路分流	各支路两端电压相等

Electrical power (P) tells you how much energy is transferred per second. P = I × V and P = E ÷ t. Fuses, circuit breakers and earth wires are safety devices that protect users from excessive current.

电功率（P）表示每秒钟传递能量的多少。P = I × V，并且 P = E ÷ t。保险丝、断路器和地线是保护用户免受过大电流危害的安全装置。

10. Waves and Radiation | 波与辐射

Waves transfer energy without transferring matter. Transverse waves (e.g. light, water waves) have oscillations perpendicular to the direction of energy travel; longitudinal waves (e.g. sound) have oscillations parallel to the travel direction.

波传递能量而不传递物质。横波（例如光波、水波）的振动方向与能量传播方向垂直；纵波（例如声波）的振动方向与传播方向平行。

Key wave properties: frequency (f, in hertz), wavelength (λ), amplitude and wave speed (v). The wave equation is:

波的关键属性：频率（f，单位赫兹）、波长（λ）、振幅和波速（v）。波速公式为：

v = f × λ

波速 = 频率 × 波长

The electromagnetic spectrum groups all transverse waves that travel at the speed of light in a vacuum (3 × 10⁸ m/s). It ranges from long‑wavelength radio waves to short‑wavelength gamma rays. Uses and dangers vary: radio waves for communication, microwaves for heating and Wi‑Fi, infrared for thermal imaging, visible light for seeing, ultraviolet for detecting forgeries but causing skin cancer, X‑rays for medical imaging, gamma rays for cancer treatment and sterilisation but high doses can damage cells.

电磁波谱涵盖了所有以光速在真空中传播（3 × 10⁸ m/s）的横波，范围从长波长的无线电波到短波长的伽马射线。用途和危害各异：无线电波用于通信，微波用于加热和Wi‑Fi，红外线用于热成像，可见光用于视觉，紫外线用于检测假钞但可导致皮肤癌，X射线用于医学成像，伽马射线用于癌症治疗和灭菌，但高剂量会损伤细胞。

Nuclear radiation originates from unstable atomic nuclei. Alpha particles (α) are helium nuclei – highly ionising but stopped by paper. Beta particles (β) are fast electrons – moderately ionising, stopped by a few millimetres of aluminium. Gamma rays (γ) are electromagnetic waves – weakly ionising, very penetrating, stopped by thick lead or concrete.

核辐射来源于不稳定的原子核。α粒子是氦原子核——电离能力强，但能被纸张挡住。β粒子是高速电子——中等电离能力，几毫米铝板可阻挡。γ射线是电磁波——电离能力弱，穿透力极强，需厚铅板或混凝土阻挡。

The half‑life of a radioactive isotope is the time taken for half the nuclei in a sample to decay. This concept is crucial for understanding radioactive dating, medical tracers and nuclear waste management.

放射性同位素的半衰期是样品中一半原子核发生衰变所需的时间。这一概念对于理解放射性定年、医学示踪剂和核废料管理至关重要。

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Core Concepts in SQA Science | SQA科学核心知识点梳理