📚 GCSE Edexcel Science: Calculation Practice | GCSE Edexcel 科学：计算题专项训练
Mastering calculations is an essential skill for GCSE Edexcel Science. Whether you are tackling Physics equations, Chemistry mole questions or Biology data analysis, a systematic approach to problem-solving will boost your confidence and marks. This article provides focused practice on key calculation types across the three sciences, with step‑by‑step guidance in both English and Chinese.
掌握计算题是 GCSE Edexcel 科学的核心技能。无论是物理公式、化学摩尔计算还是生物数据分析，系统化的解题方法都能有效提升你的信心和分数。本文针对三门科学中的关键计算题型进行专项训练，并提供中英双语的逐步指导。
1. Understanding Units and Conversions | 理解单位与转换
Start every calculation by checking the units given. Convert all quantities to SI base units—metres (m), kilograms (kg), seconds (s), amperes (A)—before substituting into any formula. This avoids errors from mixed units like cm and km.
开始任何计算前，务必检查题目所给的单位。将所有物理量转换为 SI 基本单位——米（m）、千克（kg）、秒（s）、安培（A）——然后再代入公式。这样可以避免因单位混用（如厘米和千米）而产生的错误。
Remember that areas and volumes require squaring or cubing the conversion factor. For example, to convert 5 cm2 to m2: 5 cm2 = 5 ÷ (100)2 m2 = 5 × 10⁻⁴ m2.
面积和体积的单位换算需要将进率进行平方或立方。例如，把 5 cm2 换算为 m2：5 cm2 = 5 ÷ (100)2 m2 = 5 × 10⁻⁴ m2。
Useful conversions: 1 km = 1000 m, 1 m = 100 cm, 1 kg = 1000 g, 1 tonne = 1000 kg, 1 litre = 1 dm3 = 1000 cm3.
常用换算：1 千米 = 1000 米，1 米 = 100 厘米，1 千克 = 1000 克，1 吨 = 1000 千克，1 升 = 1 dm3 = 1000 cm3。
2. Speed, Distance and Time | 速度、距离和时间
average speed = distance ÷ time
To find the distance travelled, rearrange the formula: distance = speed × time. Always ensure time is in seconds (s) if speed is in m/s.
求距离时，可重组公式：距离 = 速度 × 时间。如果速度单位是 m/s，时间必须用秒（s）。
On a distance–time graph, the gradient represents the speed. A steeper line indicates a higher speed.
在距离‑时间图像中，斜率代表速度。线越陡，速度越快。
Example: A car travels 150 km in 2 hours. Find the average speed in m/s.
Step 1: speed in km/h = 150 km ÷ 2 h = 75 km/h.
Step 2: convert to m/s by dividing by 3.6: 75 ÷ 3.6 ≈ 20.8 m/s.
示例：一辆汽车 2 小时行驶 150 km。求平均速度，单位为 m/s。
步骤 1：速度（km/h）= 150 km ÷ 2 h = 75 km/h。
步骤 2：换算为 m/s，除以 3.6：75 ÷ 3.6 ≈ 20.8 m/s。
3. Acceleration and Force | 加速度与力
acceleration (a) = (final velocity – initial velocity) ÷ time
force (F) = mass (m) × acceleration (a)
Acceleration is measured in m/s2. When using F = ma, ensure mass is in kg and acceleration in m/s2 to obtain force in newtons (N).
加速度的单位是 m/s2。使用 F = ma 时，质量必须用 kg，加速度用 m/s2，这样得到的力就是牛顿（N）。
Example: A 4 kg object accelerates from rest to 12 m/s in 3 seconds. Calculate the acceleration and the resultant force.
a = (12 – 0) / 3 = 4 m/s2. Then F = 4 × 4 = 16 N.
示例：一个 4 kg 的物体从静止加速到 12 m/s，用时 3 秒。计算加速度与合力。
a = (12 – 0) / 3 = 4 m/s2。然后 F = 4 × 4 = 16 N。
4. Density and Pressure | 密度与压强
density (ρ) = mass ÷ volume
pressure (P) = force ÷ area
Density is usually expressed in kg/m3 or g/cm3. A common pitfall is mixing g and kg with cm3 and m3—convert first.
密度通常以 kg/m3 或 g/cm3 表示。常见的错误是将 g、kg 与 cm3、m3 混用——务必先换算单位。
Pressure is measured in pascals (Pa), where 1 Pa = 1 N/m2. In solids, pressure acts over a small area to produce a large effect, explaining sharp knives and high heels.
压强的单位是帕斯卡（Pa），1 Pa = 1 N/m2。在固体中，作用在较小面积上的力会产生较大的压强，这就是刀刃和高跟鞋的原理。
Example: A block of mass 2 kg rests on a surface with an area of 0.05 m2. Taking g = 10 N/kg, force = weight = 20 N. Pressure = 20 / 0.05 = 400 Pa.
示例：一个质量为 2 kg 的木块放在面积为 0.05 m2 的表面上。取 g = 10 N/kg，力 = 重力 = 20 N。压强 = 20 / 0.05 = 400 Pa。
5. Work, Energy and Power | 功、能与功率
work done (W) = force (F) × distance (d)
power (P) = work done (W) ÷ time (t)
Energy is often calculated using gravitational potential energy (GPE) and kinetic energy (KE).
能量通常用重力势能（GPE）和动能（KE）来计算。
GPE = m × g × h
KE = ½ × m × v2
Take g = 10 N/kg on Earth unless stated otherwise. Remember that for power, the unit is the watt (W), where 1 W = 1 J/s.
除非题目另有说明，地球上的 g 取 10 N/kg。功率的单位是瓦特（W），1 W = 1 J/s。
Example: A mass of 5 kg is lifted 3 m. GPE gained = 5 × 10 × 3 = 150 J. If this takes 2 seconds, power = 150 / 2 = 75 W.
示例：将 5 kg 的物体提升 3 m。增加的 GPE = 5 × 10 × 3 = 150 J。若用时 2 秒，功率 = 150 / 2 = 75 W。
6. Electrical Circuits: Ohm’s Law and Power | 电路：欧姆定律与电功率
voltage (V) = current (I) × resistance (R)
electrical power (P) = current (I) × voltage (V) = I2 × R
energy transferred (E) = power (P) × time (t)
Always convert current to amperes (A) and resistance to ohms (Ω). Energy is usually given in joules (J), but electricity bills use kilowatt‑hours (kWh).
电流必须换算为安培（A），电阻为欧姆（Ω）。能量通常用焦耳（J）表示，但电费单用千瓦时（kWh）。
To convert joules to kWh, divide by 3.6 × 106. Pay attention to whether the time is in seconds or hours.
将焦耳转换为千瓦时，需除以 3.6 × 106。注意时间单位是秒还是小时。
Example: A 12 V lamp draws 2 A. Power = 12 × 2 = 24 W. In 5 minutes (300 s), energy used = 24 × 300 = 7200 J.
示例：一个 12 V 的灯泡通过 2 A 电流。功率 = 12 × 2 = 24 W。5 分钟（300 s）内消耗的能量 = 24 × 300 = 7200 J。
7. Moles and Molar Mass | 摩尔与摩尔质量
amount (n) = mass (m) ÷ molar mass (Mr)
The molar mass is the relative formula mass of a substance in grams per mole. Calculate Mr using the periodic table, adding the atomic masses of all atoms in the formula.
摩尔质量是物质的相对式量，单位为 g/mol。利用周期表，将化学式中所有原子的相对原子质量相加，即可得到 Mr。
For example, the Mr of H2O = (2 × 1) + 16 = 18 g/mol. To find the mass of 0.5 mol of water: mass = 0.5 × 18 = 9 g.
例如，水的 Mr = (2×1) + 16 = 18 g/mol。计算 0.5 mol 水的质量：质量 = 0.5 × 18 = 9 g。
In solids, liquids and dissolved substances, the mole relationship is fundamental to all quantitative chemistry.
在固体、液体和溶液中，摩尔关系是定量化学的基础。
8. Concentration and Titrations | 浓度与滴定
concentration (c) = amount (n) ÷ volume (V in dm3)
Concentration is often given in mol/dm3. If volume is in cm3, divide by 1000 to convert to dm3. In a titration, use the mole ratio from the balanced equation to find an unknown concentration.
浓度常用 mol/dm3 表示。若体积为 cm3，需除以 1000 转换为 dm3。在滴定中，利用配平化学方程式中的摩尔比来求未知浓度。Published by TutorHao | GCSE Science Revision Series | aleveler.com
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