(a) State what is meant by the density of a material. [1]
(b) Write the equation that links density, mass and volume. [1]
(c) Give two units in which density can be measured. [1]
A solid aluminium block has a mass of 135 g and a volume of 50 cm³. Calculate its density and give the unit.
A glass paperweight has a volume of 30 cm³. Glass has a density of 2.5 g/cm³. Calculate the mass of the paperweight.
A piece of copper has a mass of 89.6 g. Copper has a density of 8.96 g/cm³. Calculate the volume of the copper.
A learner places two objects in a beaker of water, which has a density of 1.0 g/cm³: a wax block of density 0.9 g/cm³ and a steel ball of density 7.8 g/cm³. For each object, state whether it floats or sinks and explain your answer using density.
(a) Convert a density of 2.7 g/cm³ into kg/m³. [2]
(b) Two liquids that do not mix are poured into the same jar: golden syrup of density 1.4 g/cm³ and vegetable oil of density 0.92 g/cm³. Predict which liquid floats on top and explain your prediction using density. [2]
Total: 17 marks. Original work by the TheLucidSTEM team. Written in the style of the papers; no past paper question is reproduced.
Answer key · full worked solutionsclick to reveal
(a) Density is the mass per unit volume of a material, that is the mass contained in each unit of volume.
(b) density = mass ÷ volume, written ρ = m / V.
(c) Any two of: g/cm³ and kg/m³.
ρ = m ÷ V = 135 ÷ 50 = 2.7 g/cm³.
m = ρ × V = 2.5 × 30 = 75 g.
V = m ÷ ρ = 89.6 ÷ 8.96 = 10 cm³.
Wax: floats. Its density (0.9 g/cm³) is less than the density of water (1.0 g/cm³), so it floats.
Steel: sinks. Its density (7.8 g/cm³) is greater than the density of water (1.0 g/cm³), so it sinks.
(a) 1 g/cm³ = 1000 kg/m³, so 2.7 g/cm³ = 2.7 × 1000 = 2700 kg/m³.
(b) The vegetable oil floats on top. It is less dense (0.92 g/cm³) than the golden syrup (1.4 g/cm³), and the less dense liquid floats on the denser one.