📚 Year 8 AQA Science: Formula and Theorem Quick Reference Handbook | Year 8 AQA 科学：公式定理速查手册
Welcome to your Year 8 AQA Science quick reference guide. This handbook brings together the essential formulas, equations, and key principles from physics, chemistry, and biology that you need to master by the end of the year. Use it to revise, check your understanding, and support your homework – each formula is presented with clear explanations and correct units so you can apply them confidently in lessons and assessments.
欢迎使用 Year 8 AQA 科学速查手册。本手册汇集了物理、化学、生物三科中你必须掌握的核心公式、方程式和重要原理。你可以用它来复习、检查理解水平、完成课后作业——每个公式都配有清晰的说明和正确单位，让你能够在课堂和考试中有信心地运用它们。
1. Speed, Distance and Time | 速度、距离和时间
Speed is a measure of how fast an object is moving. It can be calculated if you know the distance travelled and the time taken.
速度是衡量物体运动快慢的物理量。如果知道了移动的距离和所用的时间，便可以计算出速度。
v = s ÷ t
me (s). Speed is often measured in metres per second, but can also be given in kilometres per hour (km/h) or miles per hour (mph).
v 代表速度（单位：米/秒，m/s），s 代表距离（米，m），t 代表时间（秒，s）。速度通常用米每秒表示，也可以用千米每小时（km/h）或英里每小时（mph）表示。
ple, a car that travels 200 metres in 10 seconds has a speed of v = 200 m ÷ 10 s = 20 m/s.
例如，一辆汽车在 10 秒内行驶 200 米，其速度为 v = 200 m ÷ 10 s = 20 m/s。
2. Pressure | 压强
Pressure describes how concentrated a force is. It is the force acting per unit area of a surface.
压强描述力的集中程度，它是作用在物体单位面积上的力。
P = F ÷ A
= pressure (pascals, Pa), F = force (newtons, N), A = area (m²). 1 Pa is equal to 1 N/m².
P 表示压强（单位：帕斯卡，Pa），F 表示力（牛顿，N），A 表示受力面积（平方米，m²）。1 Pa 等于 1 N/m²。
The same force produces higher pressure when applied over a smaller area. This explains why a sharp knife cuts more easily than a blunt one.
在相同大小的力作用下，受力面积越小，压强越大。这解释了为什么锋利的刀比钝刀更容易切割。
3. Density | 密度
Density tells you how much mass is packed into a certain volume. It is a property of materials that can help identify substances.
密度表示单位体积内所含物质的质量，它是物质的一种特性，可以用来鉴别物质。
ρ = m ÷ V
(Greek letter rho) = density (kg/m³ or g/cm³), m = mass (kg or g), V = volume (m³ or cm³).
ρ（希腊字母 rho）表示密度（单位：千克/立方米 kg/m³ 或 克/立方厘米 g/cm³），m 表示质量（kg 或 g），V 表示体积（m³ 或 cm³）。
Objects with a density less than that of water (1 g/cm³) will float, while those with a higher density will sink.
密度小于水（1 g/cm³）的物体会浮在水面上，密度大于水的物体则会下沉。
4. Work Done and Energy Transfer | 做功与能量转移
Work is done whenever a force makes an object move. Energy is transferred from one store to another when work is done.
当一个力使物体移动时，我们就说力做了功。做功的同时，能量从一个储存库转移到了另一个储存库。
W = F × d
f the force (m). 1 joule is the work done when a force of 1 newton moves an object 1 metre.
W 表示做功（单位：焦耳，J），F 表示力（N），d 表示物体在力的方向上移动的距离（m）。1 焦耳相当于 1 牛顿的力使物体移动 1 米所做的功。
ook weighing 10 N through a height of 2 m, the work done against gravity is 10 × 2 = 20 J.
如果你将一本重 10 N 的书竖直向上提升 2 m，那么克服重力所做的功为 10 × 2 = 20 J。
5. Hooke's Law | 胡克定律
Hooke's Law describes the way a spring stretches. It states that the extension of a spring is directly proportional to the force applied, provided the elastic limit is not exceeded.
胡克定律描述了弹簧的拉伸规律：在弹性限度内，弹簧的伸长量与其所受的力成正比。
F = k × e
= spring constant (N/m), e = extension (m). A stiffer spring has a larger spring constant.
F 表示施加的力（N），k 是弹簧常数（N/m），e 是伸长量（m）。弹簧常数越大，弹簧越硬。
05 m when a force of 4 N is applied, its spring constant is k = F ÷ e = 4 ÷ 0.05 = 80 N/m.
如果一个弹簧在 4 N 的力作用下伸长了 0.05 m，则其弹簧常数为 k = 4 ÷ 0.05 = 80 N/m。
6. Ohm's Law | 欧姆定律
Ohm's Law links the voltage across a component, the current flowing through it, and its resistance. For many conductors at constant temperature, current is proportional to voltage.
欧姆定律将元件两端的电压、通过元件的电流和电阻联系起来。对于许多导体，在温度不变时，电流与电压成正比。
V = I × R
V = voltage (volts, V), I = current (amperes, A), R = resistance (ohms, Ω).
V 表示电压（单位：伏特，V），I 表示电流（安培，A），R 表示电阻（欧姆，Ω）。
a current of 0.4 A and a resistance of 15 Ω, the voltage across it is V = 0.4 × 15 = 6 V.
如果一盏灯的电流为 0.4 A，电阻为 15 Ω，则其两端的电压为 V = 0.4 × 15 = 6 V。
7. Electrical Charge, Current and Time | 电荷、电流和时间
The amount of electrical charge that flows in a circuit depends on the current and the time for which it flows.
电路中流动的电荷量取决于电流的大小和通电时间的长短。
Q = I × t
Q = charge (coulombs, C), I = current (A), t = time (s).
Q 表示电荷量（单位：库仑，C），I 表示电流（A），t 表示时间（s）。
A current of 2 A flowing for 30 seconds transfers a charge of Q = 2 × 30 = 60 C.
2 A 的电流流过 30 秒，转移的电荷量为 Q = 2 × 30 = 60 C。
8. Conservation of Mass in Chemical Reactions | 化学反应中的质量守恒
During a chemical reaction, atoms are rearranged but no atoms are created or destroyed. Therefore, the total mass of the reactants equals the total mass of the products.
在化学反应过程中，原子重新组合，但没有原子被创造或消失。因此，反应物的总质量等于生成物的总质量。
For example, when magnesium burns in oxygen: magnesium + oxygen → magnesium oxide.
例如，镁在氧气中燃烧：镁 + 氧气 → 氧化镁。
2Mg + O₂ → 2MgO
If you measure the mass of all reactants and products in a sealed container, the reading on the balance does not change.
如果你在密封容器中测量所有反应物和生成物的质量，天平读数将保持不变。
9. Moments (Turning Forces) | 力矩（转动效应）
A moment is the turning effect of a force. It depends on the size of the force and how far it is applied from the pivot.
力矩是力的转动效应，它取决于力的大小和作用点到支点的距离。
M = F × d
rce (N), d = perpendicular distance from the pivot to the line of action of the force (m).
M 表示力矩（单位：牛顿米，N·m），F 表示力（N），d 表示从支点到力作用线的垂直距离（m）。
For a seesaw to balance, the total clockwise moment must equal the total anticlockwise moment.
要使跷跷板平衡，顺时针力矩的总和必须等于逆时针力矩的总和。
10. Weight and Mass | 重量与质量
Mass is the amount of matter in an object and is measured in kilograms. Weight is the force of gravity acting on that mass.
质量是物体所含物质的多少，单位是千克。重量是作用在该质量上的重力。
W = m × g
field strength (N/kg). On Earth, g ≈ 9.8 N/kg, often rounded to 10 N/kg for calculations.
W 表示重量（N），m 表示质量（kg），g 表示重力场强度（N/kg）。在地球表面，g 约等于 9.8 N/kg，计算时常常取 10 N/kg。
mately 50 N (5 × 10). On the Moon, where g ≈ 1.6 N/kg, its weight would be only about 8 N.
一个 5 kg 的物体在地球上的重量约为 50 N（5 × 10）。而在月球上，g 约等于 1.6 N/kg，它的重量仅为约 8 N。
11. Respiration Equation | 呼吸作用方程式
Aerobic respiration is the chemical reaction that releases energy from glucose in the presence of oxygen. This energy is used for all living processes.
有氧呼吸是在氧气参与下，从葡萄糖中释放能量的化学反应。这些能量用于维持一切生命活动。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ energy)
Glucose and oxygen react to produce carbon dioxide, water and energy. Respiration takes place continuously in the mitochondria of plant and animal cells.
葡萄糖与氧气反应，生成二氧化碳、水和能量。呼吸作用在动植物细胞的线粒体中持续进行。
12. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which green plants and some other organisms use light energy to convert carbon dioxide and water into glucose and oxygen.
光合作用是绿色植物和某些其他生物利用光能，将二氧化碳和水转化为葡萄糖和氧气的过程。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Light energy is absorbed by chlorophyll in chloroplasts. The glucose produced can be used immediately for respiration or stored as starch.
叶绿体中的叶绿素吸收光能。生成的葡萄糖可以立即用于呼吸作用，或转化为淀粉储存起来。
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