Question

(a) Write down an equation that defines density.
(b) 5 kg of material A occupy 20 cm³ whereas 20 kg of material B occupy 90 cm³. Which has the greater density : A or B? Support your answer with calculations.

Answer 1

Density is defined by the following equation:
$\rho =\frac{m}{V}$,
where ρ = density,
V = volume, and
m = mass.

(b)
ρ (density of material A) = ?
V (volume of material A) = 20 cm³
m (mass of material A) = 5 kg = 5 × 1,000 = 5,000 g
$$\begin{gathered} \rho =\frac{m}{V} \\ =\frac{5,000}{20} \end{gathered}$$

ρ = 250 g/cm³
Ans: Density of material A = 250 g/cm³.

ρ (density of material B) = ?
V (volume of material B) = 90 cm³
m (mass of material B) = 20 kg = 20 × 1,000 = 20,000 g
$$\begin{gathered} \rho =\frac{m}{V} \\ =\frac{20,000}{90} \end{gathered}$$
ρ = 222.222 g/cm³
Answer: Density of material B = 222.22 g/cm³.
A has greater density.