---
title: "Density and How to Measure It"
description: "Density is mass per unit volume, found by weighing and by measuring volume, including displacement for an awkward shape. Particle spacing explains why the same substance has a much lower density as a "
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source: https://lightmysky.com/learn/science/density-and-how-to-measure-it-mt_HrKI1-UzfI.md
retrieved: 2026-09-12
---

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# Density and How to Measure It

Density is mass per unit volume, found by weighing and by measuring volume, including displacement for an awkward shape. Particle spacing explains why the same substance has a much lower density as a gas.

Subject: Science · Area: Matter & Materials · Ages 15 to 16
Page: https://lightmysky.com/learn/science/density-and-how-to-measure-it-mt_HrKI1-UzfI

## Ready when they can

- Calculates density in kg per cubic metre or g per cubic centimetre and rearranges for mass or volume
- Measures the volume of an irregular solid by displacement and reports its density
- Uses particle spacing to explain the density order of a solid, a liquid and a gas

## Lesson: Packing mass into volume

Density packs mass and volume into one number. Divide mass by volume to get it, in kilograms per cubic metre or grams per cubic centimetre. Flip the link to find mass from density times volume, or volume from mass over density.

**Example.** Tom measures a strange stone. He weighs it on a balance, then lowers it into a measuring cylinder and reads how far the water level rises. That rise equals the volume of the stone. He divides mass by that volume and compares the answer with known values.

Particles explain the usual order of densities. Solids pack tightly, liquids sit looser, and gas particles fly far apart with mostly empty space. The same particles with wider spacing always mean lower density. Floating is a density contest, since denser fluids push harder on what they hold.

**Tip.** Two objects can share a mass yet differ wildly in density if their volumes differ. Always divide before you judge. A big light box can hold the same mass as one small heavy bolt.

**Recap.** Density is mass over volume, and spacing decides its size.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [The Particle Model](https://lightmysky.com/learn/science/the-particle-model-mt_b6kZgqolEd)
- [Specific Heat Capacity as a Material Property](https://lightmysky.com/learn/science/specific-heat-capacity-as-a-material-property-mt_mXC9IKom3P)

## Opens up

- [Pressure in Liquids and the Atmosphere](https://lightmysky.com/learn/science/pressure-in-liquids-and-the-atmosphere-mt_eLGNkEJAZl)
- [Uncertainty, Precision and Significant Figures in a Measurement](https://lightmysky.com/learn/science/uncertainty-precision-and-significant-figures-in-a-measurement-mt_HPc3OahYoV)
- [Stress, Strain and the Young Modulus](https://lightmysky.com/learn/science/stress-strain-and-the-young-modulus-mt_uWdqhWGT7Y)