Page 83 - Physics

Density and relative density

Chapter Four

Density and relative density

Introducti on

Density is an important concept for scientists and engineers because it is
useful in determining the characteristics of a material. Engineers must think
of the density of the materials before marine and air transport vessels can be
designed and built so that they will fl oat. For example, aluminium alloy as
one of the materials used in aircraft construction substituted steel because
aluminium is less dense than steel. In this chapter, you will learn the concept
of density, how to determine the densities of solids and liquids, the concept
of relative density and the determination of the relative density of solids and
liquids. The competencies developed are useful in designing and constructing
of models for marine and air transport vessels so that they will fl oat. Moreover,
you will acquire skills in identifying the purity of a substance and estimating
the composition of different types of mixtures.

Think
how concept of density can be used in designing marine and air transport
vessels

Concept of density
Suppose you measure the mass of three blocks made up of glass, iron and wood whose
size are identical shown in Figure 4.1. You will fi nd that the masses of all blocks are
different although their volumes are similar.

Glass Iron Wood
Figure 4.1 Blocks of glass, iron, and wood

The iron block will have a greater mass than the glass block which has a greater mass
than the wooden block. The difference in mass arises from the way the particles of the
blocks are packed together. This suggests that a comparison of the mass of a substance

77

Physics Form 1 Final.indd 77 16/10/2024 20:56