Solids, Liquids and Gases
6 marks · NormalA science teacher uses an ice block and an iron block to demonstrate differences in properties of solids and liquids. She measures the volume and mass of both blocks. Later, she places the iron block on a wooden bench and the ice block in water.
State the equation to calculate the density of a substance, and name the correct SI unit for density.
The iron block has a mass of 1.20 kg and a volume of 1.5 × 10⁻⁴ m³. Calculate the density of the iron block.
When the iron block is placed on a wooden bench, it exerts a force of 12 N over an area of 0.006 m². Calculate the pressure applied to the bench by the iron block. Give your answer in Pa.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) density = mass / volume; SI unit is kg/m³
(b) 8000 kg/m³
(c) 2000 Pa
Common mistakes: Using g/cm³ instead of kg/m³; Forgetting to convert area/mass units
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · States correct density formula: density = mass/volume
A1 (a) · 1 mark · Names correct SI unit: kg/m³
M2 (b) · 1 mark · Substitutes values correctly into formula or shows correct arrangement
A2 (b) · 1 mark · Evaluates density as 8000 kg/m³ (accept nearest integer/rounded value)
M3 (c) · 1 mark · Substitutes values into pressure formula or rearranges
A3 (c) · 1 mark · Evaluates as 2000 Pa (accept answers between 1990–2010)
Worked solution
a) The density of a substance is calculated as:
SI unit for density is kg/m³.
b) Density = 1.20 kg / (1.5 × 10⁻⁴ m³)
c) Pressure = Force / Area = 12 N / 0.006 m² = 2000 Pa