📚 IGCSE Edexcel Science: Formula Handbook | IGCSE Edexcel 科学：公式汇总手册
This handbook brings together every key equation you need for IGCSE Edexcel Science – Physics, Chemistry and Biology. Work through it step by step to sharpen your numerical skills and boost your exam confidence.
本手册汇总了 IGCSE Edexcel 科学（物理、化学、生物）所有关键公式。循序渐进地练习这些计算，能有效提升你的实考信心。
1. Speed and Acceleration | 速度与加速度
Average speed is the total distance travelled divided by the total time taken. The standard unit is metres per second (m/s).
平均速度等于物体运动的总距离除以总时间，常用单位为米每秒 (m/s)。
v = s / t
Acceleration measures how quickly velocity changes. It is the change in velocity divided by the time over which that change occurs.
加速度衡量速度变化的快慢，等于速度变化量除以发生这一变化所用的时间。
a = (v − u) / t
For uniformly accelerated motion, the final velocity v can be found from the initial velocity u, the constant acceleration a and the displacement s.
对于匀加速直线运动，未速度 v 可以利用初速度 u、加速度 a 和位移 s 求出。
v² = u² + 2as
Displacement during uniform acceleration can also be expressed using the average of the initial and final velocities.
匀加速运动中的位移也可以用初、未速度的平均值来表示。
s = (u + v) t / 2
2. Force, Mass and Momentum | 力、质量与动量
Newton's second law states that the net force acting on an object equals the product of its mass and acceleration.
牛顿第二定律指出，作用在物体上的合力等于物体的质量与其加速度的乘积。
F = m a
Weight is the gravitational force on a mass. On Earth, the gravitational field strength g is approximately 10 N/kg (or 9.8 N/kg).
重量是质量受到的引力；地球表面的引力场强度 g 约为 10 N/kg（或 9.8 N/kg）。
W = m g
Momentum is the product of mass and velocity. It is a vector quantity, conserved in collisions and explosions when no external force acts.
动量等于质量与速度的乘积，是矢量。在没有外力作用时，碰撞和爆炸过程中动量守恒。
p = m v
The rate of change of momentum gives the net force acting on an object.
动量随时间的变化率等于物体所受的合力。
F = (mv − mu) / t
Hooke's law describes the extension of a spring within its elastic limit.
胡克定律描述了弹簧在弹性限度内的伸长量。
F = k x
3. Energy, Work and Power | 能量、功和功率
Work done is the energy transferred when a force moves through a distance in the direction of the force.
力在其作用方向上使物体移动一段距离时就做了功，功等于能量转移。
W = F d
Kinetic energy (KE) depends on mass and the square of speed.
动能取决于质量和速度的平方。
KE = ½ m v²
Gravitational potential energy (GPE) gained when lifting an object is proportional to mass, gravitational field strength and height.
提升物体时所增加的重力势能与质量、引力场强度和高度成正比。
GPE = m g h
Power is the rate of doing work or transferring energy. One watt is one joule per second.
功率是做功或能量转移的速率，1 瓦特等于 1 焦耳每秒。
P = W / t
Efficiency compares useful output energy or power to total input. It is often expressed as a percentage.
效率比较有用输出能量（或功率）与总输入能量（或功率）之比，常用百分数表示。
Efficiency = (useful output / total input) × 100%
4. Density and Pressure | 密度与压强
Density is mass per unit volume; the standard unit is kg/m³.
密度是单位体积的质量，标准单位为 kg/m³。
ρ = m / V
Pressure acting on a surface is force per unit area. The unit is the pascal (Pa), equal to N/m².
作用于表面的压强等于单位面积上的力，单位是帕斯卡 (Pa)，即 N/m²。
p = F / A
For a column of liquid, pressure depends on the fluid density, gravitational field strength and the depth.
对于液柱，压强取决于液体密度、引力场强度和深度。
p = h ρ g
5. Electricity | 电学
Ohm's law links the potential difference across a conductor to the current and resistance.
欧姆定律将导体两端的电势差与电流和电阻联系起来。
V = I R
Electric charge transferred depends on current and time.
转移的电荷量取决于电流大小和通电时间。
Q = I t
Electrical power can be calculated from current and voltage, and also from current squared times resistance.
电功率可以由电流与电压的乘积求得，也可用电流的平方乘以电阻计算。
P = I V
P = I² R
Energy transferred electrically is the product of power and time.
电能转移等于电功率与时间的乘积。
E = P t
For resistors in series, total resistance is the sum; for two resistors in parallel, the product over sum rule applies.
串联电阻的总阻值为各电阻之和；两个电阻并联时，可用积/和公式。
Rtotal = R₁ + R₂ (series)
1/Rtotal = 1/R₁ + 1/R₂ (parallel)
6. Waves | 波
The speed of a wave is the product of its frequency and wavelength.
波速等于频率与波长的乘积。
v = f λ
The period of a wave is the reciprocal of the frequency.
波的周期是频率的倒数。
T = 1 / f
When light travels from a medium into another, the refractive index n relates the angles of incidence and refraction.
光从一种介质进入另一种介质时，折射率 n 将入射角和折射角联系起来。
n = sin i / sin r
The critical angle for total internal reflection can be found if the refractive index is known.
已知折射率时可求出全反射的临界角。
sin c = 1 / n
The refractive index also equals the ratio of the speed of light in vacuum to the speed in the medium.
折射率也等于真空光速与介质中光速之比。
n = c / v
7. The Mole Concept (Chemistry) | 摩尔概念（化学）
The amount of substance, measured in moles (n), connects mass (m) and molar mass (M).
物质的量（n，单位摩尔）将质量 (m) 与摩尔质量 (M) 联系起来。
n = m / M
At room temperature and pressure (RTP), one mole of any gas occupies 24 dm³.
在常温常压 (RTP) 下，1 摩尔任何气体的体积为 24 dm³。
n = V(gas) / 24 dm³
Concentration of a solution is the amount of solute per unit volume; it is usually expressed in mol/dm³.
溶液的浓度为溶质的物质的量除以溶液体积，常用 mol/dm³ 表示。
c = n / V
The percentage by mass of an element in a compound can be determined from the relative formula masses.
化合物中某元素的质量分数可通过相对式量计算。
% mass = (total mass of element / Mr of compound) × 100
8. Titrations and Reacting Masses | 滴定与反应质量
In a titration, the unknown concentration is found using the equation caVa / cbVb = na / nb, where n refers to the stoichiometric coefficients.
滴定中可利用化学计量数之比求出未知浓度：caVa / cbVb = na / nb。
c₁V₁ / n₁ = c₂V₂ / n₂
Reacting masses are calculated by converting mass to moles, scaling by the mole ratio from the balanced equation, and converting back to mass.
反应质量的计算步骤：质量转摩尔 → 用化学计量比转换 → 摩尔转回质量。
mass A → mol A → mol B → mass B
The volume of gas produced in a reaction can be predicted from the moles of a reactant at RTP.
反应产生的气体体积可根据反应物的摩尔数以及 RTP 下的摩尔体积来预测。
V(gas) = n × 24 dm³
9. Energy Changes in Reactions | 反应中的能量变化
The heat energy change in a solution is calculated using the mass, specific heat capacity and temperature change.
溶液中的热量变化通过质量、比热容与温度变化计算。
q = m c ΔT
The molar enthalpy change ΔH is the heat change per mole of a specified reactant or product.
摩尔焓变 ΔH 是每摩尔指定反应物或产物的热量变化。
ΔH = −q / n
A negative ΔH indicates an exothermic reaction; a positive ΔH indicates an endothermic reaction.
ΔH 为负表示放热反应，ΔH 为正表示吸热反应。
10. Quantitative Biology | 生物学中的定量关系
Magnification is the ratio of image size to actual size. The formula can be rearranged to find any missing value.
放大倍数为图像尺寸与实际尺寸之比，这个公式可以变形求任一未知量。
Magnification = image size / actual size
Energy transfer efficiency between trophic levels is expressed as a percentage.
营养级之间的能量传递效率用百分数表示。
Efficiency = (energy available after transfer / energy available before transfer) × 100%
Rate of reaction or rate of photosynthesis can be measured as the reciprocal of time taken for a certain change to occur.
反应速率或光合作用速率可用发生特定变化所需时间的倒数来衡量。
Rate = 1 / time
g Cardiac output and breathing rate calculations also use simple products: cardiac output = heart rate × stroke volume.
心输出量等也可用简单乘积计算：心输出量 = 心率 × 每搏输出量。
Q = heart rate × SV
Percentage change calculations appear across all sciences to compare initial and final values.
百分比变化计算在所有科学学科中都用于比较初值与终值。
% change = (final − initial) / initial × 100
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