Number Systems in IGCSE Science: Units, Standard Form and Significant Figures | IGCSE科学中的数字系统：单位、标准形式与有效数字

📚 Number Systems in IGCSE Science: Units, Standard Form and Significant Figures | IGCSE科学中的数字系统：单位、标准形式与有效数字

Numbers are the language of measurement in science. Every observation in IGCSE Science must be recorded as a number together with its unit. Without a unit, a measurement has no scientific meaning. Cambridge IGCSE Science tests your ability to handle numbers accurately through unit conversions, standard form, significant figures, estimation and practical data recording.

数字是科学测量的语言。在IGCSE科学中，每一个观察结果都必须记录为数字和单位。没有单位的测量在科学上没有意义。剑桥IGCSE科学考查你准确处理数字的能力，包括单位换算、标准形式、有效数字、估算和实验数据记录。

1. Why Numbers Matter in Science | 为什么数字在科学中重要

In science, a number is never enough by itself. If you write ‘length = 5’, the reader does not know whether you mean 5 metres, 5 centimetres or 5 kilometres. This is why every measurement must have both a numerical value and a unit. Numeracy skills are assessed throughout the Cambridge IGCSE Science papers, from multiple-choice questions to long practical investigations.

在科学中，仅有数字是远远不够的。如果你写 ‘长度 = 5’，读者不知道你指的是 5 米、5 厘米还是 5 千米。这就是为什么每个测量值都必须同时具有数值和单位。数字技能贯穿剑桥IGCSE科学试卷的考查，从选择题到长实验探究题都涉及。

You also need to decide how precise a measurement is. The number of digits you write tells others how reliable your data is. Writing too many digits suggests false precision, while writing too few loses useful information. This balance is a key part of scientific communication.

你还需要判断一个测量值的精密度。你写出的位数告诉别人你的数据有多可靠。写太多位数意味着虚假的精密度，而写太少则丢失了有用的信息。这种平衡是科学交流的关键部分。

2. SI Base Units and Prefixes | 国际单位制基本单位与词头

The International System of Units (SI) gives scientists a shared set of base units. For Cambridge IGCSE Science, the most common base units are the metre (m) for length, the kilogram (kg) for mass, the second (s) for time, the ampere (A) for electric current, the kelvin (K) for temperature and the mole (mol) for amount of substance.

国际单位制（SI）为科学家提供了一套共同的基本单位。对于剑桥IGCSE科学来说，最常见的基本单位是长度单位米（m）、质量单位千克（kg）、时间单位秒（s）、电流单位安培（A）、温度单位开尔文（K）和物质的量单位摩尔（mol）。

Prefixes are attached to base units to express very large or very small values conveniently. A kilometre is 10³ metres, a millimetre is 10⁻³ metres, and a nanometre is 10⁻⁹ metres. The table below shows the prefixes you should know for IGCSE Science.

词头附加在基本单位上，以方便地表示非常大或非常小的值。一千米是 10³ 米，一毫米是 10⁻³ 米，一纳米是 10⁻⁹ 米。下表列出了IGCSE科学中你需要掌握的词头。

3. Derived Units and Their Symbols | 导出单位及其符号

Many quantities in IGCSE Science are expressed in derived units made by combining base units. Speed is measured in metres per second (m s⁻¹). Density is measured in kilograms per cubic metre (kg m⁻³). Force uses the newton (N), where 1 N = 1 kg m s⁻².

IGCSE科学中的许多量使用由基本单位组合而成的导出单位来表示。速度的单位是米每秒（m s⁻¹）。密度的单位是千克每立方米（kg m⁻³）。力使用牛顿（N），其中 1 N = 1 kg m s⁻²。

Energy uses the joule (J), pressure uses the pascal (Pa), and power uses the watt (W). Their relationships are shown below. Electrical measurements introduce other derived units such as the volt (V), the ohm (Ω) and the hertz (Hz) for frequency.

能量使用焦耳（J），压强使用帕斯卡（Pa），功率使用瓦特（W）。它们的关系如下所示。电学测量还引入了其他导出单位，如电压单位伏特（V）、电阻单位欧姆（Ω）和频率单位赫兹（Hz）。

1 J = 1 N m = 1 kg m² s⁻² 1 W = 1 J s⁻¹ 1 Pa =

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