Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want density — the formula, units and floating rules — to become a reliable source of marks instead of a rearrangement puzzle.
What query it owns: how to understand and revise density in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the density revision-guide angle, while Tutopiya’s Density subtopic page owns the learning resource and the free Density quiz owns the practice.

Density tells you how much mass is packed into a given volume. Cambridge IGCSE Coordinated Science (0654) expects you to use ρ = m/V, convert units correctly, and predict whether objects float or sink. This guide links the formula to the practical and calculation questions examiners set every year.

Key takeaways

• Density = mass ÷ volume → ρ = m/V.
• SI unit: kg/m³; also used: g/cm³ (1 g/cm³ = 1000 kg/m³).
• Water has density ≈ 1 g/cm³ (1000 kg/m³).
• An object floats if its density is less than the liquid; sinks if greater.
• Volume of a regular solid: V = length × width × height; irregular solids use displacement.

What is density in Cambridge IGCSE Coordinated Science?

Density is a property of a substance — pure water always has the same density at a given temperature. Heavier (more dense) substances have more mass per unit volume. Comparing densities tells you whether an object floats: a cork floats on water because cork is less dense than water; an iron nail sinks because iron is denser.

You can read the full explanation, diagrams and notes on Tutopiya’s Density subtopic page before you attempt questions.

The density equation and unit conversions

Form	Use when
ρ = m/V	Finding density from mass and volume
m = ρV	Finding mass
V = m/ρ	Finding volume

Unit tip: 1 g/cm³ = 1000 kg/m³. Convert cm³ to m³ by dividing by 1 000 000 (or keep g and cm³ together).

Floating and sinking — the rule

Comparison	Result
Object density < liquid density	Floats
Object density = liquid density	Suspended (neither floats nor sinks)
Object density > liquid density	Sinks

Density in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical density stem
Calculate	Use ρ = m/V	”Calculate the density of the block.”
Define	Give precise meaning	”Define density.”
Explain	Link density to observation	”Explain why the oil floats on water.”
Determine volume	Measure or calculate V	Displacement method for irregular objects

Worked exam-style stems (how to answer the wording)

1. “A block has mass 200 g and volume 50 cm³. Calculate its density.” ρ = m/V = 200/50 = 4 g/cm³. Mark-scheme reward: correct calculation and unit.
2. “Define density.” Mass per unit volume. Reward: mass + per unit volume.
3. “An object has density 0.8 g/cm³. State whether it floats or sinks in water.” Floats — its density is less than water (1 g/cm³). Reward: floats + correct comparison.

Test yourself with the Density quiz once you can calculate density and predict floating behaviour.

How density connects to the rest of Coordinated Science physics

Density builds on Mass And Weight and Length And Time for accurate measurement. It links to The Particulate Nature of Matter — gases are less dense than liquids. The Cambridge IGCSE Coordinated Science resource hub links every Motion subtopic.

Common mistakes students make

• Dividing volume by mass instead of mass by volume.
• Mixing units — e.g. grams with m³ without converting.
• Forgetting water density is 1 g/cm³ when comparing floating.
• Using weight instead of mass in ρ = m/V.
• Not converting cm³ to m³ when the answer must be in kg/m³.

When you need more support

If density questions keep costing marks, work through the Density quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is density hard in Coordinated Science? One formula and one floating rule cover most questions — unit conversion is the main challenge.

What is the formula for density? ρ = m/V — density equals mass divided by volume.

Why does oil float on water? Oil is less dense than water (density less than 1 g/cm³).

How do I revise density effectively? Practise ρ = m/V calculations, learn the floating rule, then take the Density quiz.

Ready to master Cambridge IGCSE Coordinated Science density?

Start with the Density subtopic page, then book a free trial with a Cambridge IGCSE Coordinated Science specialist to turn density calculations into guaranteed marks.

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