📚 Year 8 SQA Science: Formula & Theorem Quick Reference Handbook | Year 8 SQA 科学：公式定理速查手册
This quick reference handbook compiles the essential formulas, equations and scientific theorems needed for the Year 8 SQA Science curriculum. Covering physics, chemistry and biology, it is designed to help you revise key relationships involving speed, density, forces, energy, electricity, chemical reactions and biological processes. Use it as a rapid checklist to ensure you know how to apply each principle and its units correctly.
这本速查手册汇编了 Year 8 SQA 科学课程所必需的核心公式、方程和科学定理。它涵盖物理、化学和生物，旨在帮助你复习速度、密度、力、能量、电学、化学反应以及生命过程等方面的关键关系。把它用作快速检查清单，确保你正确掌握每个原理的应用及其单位。
1. Speed, Distance and Time | 速度、距离与时间
The average speed of an object can be found using the formula v = d / t, where v is speed, d is distance travelled, and t is the time taken.
物体的平均速度可用公式 v = d / t 求出，其中 v 为速度，d 为通过的距离，t 为所用时间。
Speed is measured in metres per second (m/s), distance in metres (m) and time in seconds (s).
速度的单位是米/秒（m/s），距离的单位是米（m），时间的单位是秒（s）。
If you need to find distance or time, rearrange the equation: d = v × t and t = d / v.
如需计算距离或时间，可变形公式：d = v × t 和 t = d / v。
On a distance–time graph, a straight line represents constant speed; the steeper the line, the greater the speed.
在距离‑时间图中，直线代表匀速运动；直线越陡，速度越大。
2. Density, Mass and Volume | 密度、质量与体积
Density measures how much mass is packed into a given volume and is given by ρ = m / V, where ρ is density, m is mass and V is volume.
密度衡量单位体积内所含质量的大小，公式为 ρ = m / V，ρ 为密度，m 为质量，V 为体积。
Common units are kilograms per cubic metre (kg/m³) and grams per cubic centimetre (g/cm³). The density of water is 1 g/cm³ (or 1000 kg/m³).
常用单位是千克/立方米（kg/m³）和克/立方厘米（g/cm³）。水的密度为 1 g/cm³（即 1000 kg/m³）。
An object floats if its density is less than the density of the fluid it is placed in; it sinks if its density is greater.
物体的密度小于所在流体的密度时会漂浮，大于时则会下沉。
3. Force, Mass and Acceleration (Newton’s Second Law) | 力、质量与加速度（牛顿第二定律）
Newton’s Second Law states that the resultant force acting on an object is equal to the object’s mass multiplied by its acceleration: F = m × a.
牛顿第二定律指出，作用在物体上的合力等于物体的质量乘以其加速度：F = m × a。
Force is measured in newtons (N), mass in kilograms (kg) and acceleration in metres per second squared (m/s²).
力的单位是牛顿（N），质量的单位是千克（kg），加速度的单位是米/秒²（m/s²）。
On Earth’s surface, the weight of an object is a special case: W = m × g, where g ≈ 9.8 N/kg (often rounded to 10 N/kg).
在地球表面，物体的重量是一个特例：W = m × g，其中 g ≈ 9.8 N/kg（常近似为 10 N/kg）。
4. Pressure, Force and Area | 压强、力与面积
Pressure tells us how concentrated a force is on a surface: P = F / A, where P is pressure, F is force and A is the area over which the force acts.
压强表示力在表面上的集中程度：P = F / A，P 为压强，F 为力，A 为受力面积。
Pressure is measured in pascals (Pa); 1 Pa = 1 N/m².
压强的单位是帕斯卡（Pa）；1 Pa = 1 N/m²。
For a constant force, increasing the area reduces the pressure, which explains why snowshoes prevent sinking into soft snow.
力一定时，增大受力面积会减小压强，这就是雪鞋能防止陷入松软雪地的原理。
5. Ohm’s Law (Voltage, Current and Resistance) | 欧姆定律（电压、电流与电阻）
Ohm’s Law relates the voltage across a conductor to the current flowing through it and its resistance: V = I × R.
欧姆定律描述了导体两端的电压与流过它的电流及其电阻的关系：V = I × R。
V is voltage in volts (V), I is current in amperes (A), and R is resistance in ohms (Ω).
V 为电压，单位伏特（V）；I 为电流，单位安培（A）；R 为电阻，单位欧姆（Ω）。
You can also write I = V / R and R = V / I, making it easy to find the missing quantity in a circuit.
也可变形为 I = V / R 和 R = V / I，便于在电路中求未知量。
6. Work, Energy and Power | 功、能量与功率
Work is done when a force moves an object in the direction of the force: W = F × d. Work and energy are both measured in joules (J).
当力使物体沿力的方向移动时，力做了功：W = F × d。功和能量均以焦耳（J）为单位。
Power is the rate of doing work or transferring energy: P = W / t (or P = ΔE / t). Power is measured in watts (W), where 1 W = 1 J/s.
功率是做功或转移能量的速率：P = W / t（或 P = ΔE / t）。功率的单位是瓦特（W），1 W = 1 J/s。
7. Kinetic and Potential Energy | 动能与势能
Kinetic energy is the energy of motion: Eₖ = ½ m v², where m is mass (kg) and v is speed (m/s).
动能是运动的能量：Eₖ = ½ m v²，m 为质量（kg），v 为速度（m/s）。
Gravitational potential energy (GPE) depends on height, mass and gravity: Eₚ = m g h, where h is height (m) and g = 9.8 N/kg.
重力势能（GPE）取决于高度、质量和引力场强：Eₚ = m g h，h 为高度（m），g = 9.8 N/kg。
8. Law of Conservation of Energy | 能量守恒定律
Energy cannot be created or destroyed; it can only be transferred, stored or transformed from one form to another.
能量既不能被创造，也不能被消灭；它只能被转移、储存或从一种形式转化为另一种形式。
In a pendulum swing, GPE converts to kinetic energy and back again, but the total energy remains constant if we ignore air resistance.
在单摆运动中，重力势能转化为动能，再转化回来，若忽略空气阻力，总能量保持不变。
9. Chemical Reactions and Conservation of Mass | 化学反应与质量守恒
During a chemical reaction, atoms are rearranged to form new substances, but no atoms are gained or lost. The total mass of reactants equals the total mass of products.
在化学反应中，原子重新排列形成新物质，但原子不会凭空产生或消失。反应物的总质量等于生成物的总质量。
Word equations and symbol equations must be balanced to show this conservation of mass.
文字方程式和符号方程式必须配平以体现质量守恒。
10. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen.
光合作用是植物将光能转化为化学能、产生葡萄糖和氧气的过程。
The balanced summary equation is:
配平的简式方程式为：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
(Light energy and chlorophyll are required above the arrow.)
（箭头上方需写光照和叶绿素。）
11. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration releases energy from glucose in the presence of oxygen. It occurs in the mitochondria of cells.
有氧呼吸在氧气存在下从葡萄糖释放能量。该过程发生在细胞的线粒体中。
The word equation is: glucose + oxygen → carbon dioxide + water + energy (ATP).
文字方程式为：葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量（ATP）。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
12. Cell Theory and Magnification | 细胞学说与放大倍数
The cell theory states that all living things are made of cells, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells.
细胞学说指出：所有生物都由细胞构成，细胞是结构和功能的基本单位，所有细胞都来源于已存在的细胞。
When using a light microscope, the total magnification is calculated as: magnification = eyepiece lens × objective lens.
使用光学显微镜时，总放大倍数计算公式为：放大倍数 = 目镜放大倍数 × 物镜放大倍数。
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