GCSE Physics: Density of materials

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1. What is the equation for the density of a material?

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   ρ = m / V (density = mass ÷ volume).

2. What is the SI unit of density?

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   Kilograms per metre cubed, kg/m³.

3. Which Greek letter is the symbol for density?

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   ρ (rho).

4. Density is mass divided by ?.

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   volume

5. What unit must volume be in when calculating density in kg/m³?

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   Metres cubed, m³.

6. Which model explains why different states of matter have different densities?

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   The particle model — density depends on how closely the atoms or molecules are arranged.

7. Why is a gas much less dense than the same substance as a solid?

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   In a gas the particles are far apart, so there is less mass in each unit of volume; in a solid the particles are closely packed.

8. How is the volume of a regularly shaped solid found when measuring its density?

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   By measuring its dimensions (e.g. with a ruler, micrometer or Vernier callipers) and calculating the volume.

9. How is the volume of an irregularly shaped solid found when measuring its density?

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   By a displacement technique — submerge it in water and measure the volume of water displaced.

10. Name an instrument more precise than a ruler for measuring the dimensions of a small object.

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    A micrometer or Vernier callipers.

11. When applying the density equation to a change, what quantity is assumed to be conserved?

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    Mass — the equation ρ = m/V is applied to changes where mass stays the same (e.g. a change of state).