Density and the density practical – IGCSE Physics exam questions with mark scheme

1Grade 1–34 marks

A student has a metal block measuring 5.0 cm × 4.0 cm × 10.0 cm. The mass of the block is 540 g.

(a) State the equation linking density, mass and volume. [1]

(b) Calculate the density of the metal. Give the unit. [3]

(a) density = mass ÷ volume; accept $\rho = \dfrac{m}{V}$ or rearranged forms; do not accept a triangle with no equation(1)
(b) volume = 5.0 × 4.0 × 10.0 = 200 (cm³)(1)
(b) density = 540 ÷ 200 (evaluation) = 2.7(1)
(b) g/cm³; accept 2700 kg/m³ for both final marks(1)
Answer: (a) density = mass ÷ volume (b) 2.7 g/cm³
Examiner tip: The unit mark is lost when students write 'g/cm' or leave it out; work out the volume first and keep it in cm³.

2Grade 4–56 marks

A student wants to find the density of a small, irregularly shaped stone.

(a) Describe how the student could use a measuring cylinder, water and a balance to determine the density of the stone. [5]

(b) Suggest one way the student could make the measurement of volume more accurate. [1]

(a) measure the mass of the stone using the (top-pan) balance(1)
(a) part-fill the measuring cylinder with water and record the volume(1)
(a) lower/place the stone into the water so it is fully submerged and record the new volume(1)
(a) volume of stone = new reading − initial reading(1)
(a) density = mass ÷ volume (of stone)(1)
(b) read the meniscus at eye level / use a narrower measuring cylinder with finer scale / repeat and take a mean / lower stone gently on a thread to avoid splashing; any one(1)
Answer: Mass on balance; volume by displacement (difference in readings); density = mass ÷ volume.
Examiner tip: Students often forget to say the stone must be fully submerged or to subtract the initial reading.

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