Measuring Density: Techniques and Calculations for A-Level Physics | 密度的测量与计算技巧

📚 Measuring Density: Techniques and Calculations for A-Level Physics | 密度的测量与计算技巧

Density is a fundamental physical property that relates the mass of a substance to the volume it occupies. In A-Level physics, accurate density measurement is essential for identifying materials, analysing fluid behaviour and solving problems involving buoyancy. This guide covers all the core techniques you need, from regular solid blocks to liquids, gases and modern applications.

密度是连接物体质量与其所占体积的基本物理性质。在 A-Level 物理中，准确的密度测量对于鉴别材料、分析流体行为以及解决浮力相关问题都至关重要。本指南涵盖所有核心技巧，从规则固体块到液体、气体及现代应用。

1. Density Basics | 密度基础

Density (ρ) is defined as the mass per unit volume of a material. The fundamental equation is

密度（ρ）定义为单位体积内所含的质量。基本公式为

ρ = m / V

where m is the mass in kilograms (kg) and V is the volume in cubic metres (m³). The SI unit of density is therefore kg/m³. In many laboratory calculations, g/cm³ is used instead. Remember that 1 g/cm³ = 1000 kg/m³.

其中 m 是质量（单位为千克 kg），V 是体积（单位为立方米 m³）。因此密度的 SI 单位是 kg/m³。在许多实验室计算中，常用 g/cm³。请记住 1 g/cm³ = 1000 kg/m³。

Density is an intensive property: it does not depend on the amount of substance present. However, temperature affects density because most materials expand when heated. For assessments, you should quote density to an appropriate number of significant figures

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