The mass per unit volume of a substance is called density $(density = mass/volume)$. Arrange the following in order of increasing density: air, exhaust from chimneys, honey, water, chalk, cotton, and iron.

(N/A) Density is defined as the mass per unit volume of a substance. Generally, the density of states of matter follows the order: $Gas < Liquid < Solid$.
$1$. Air and exhaust from chimneys are gases, which have the lowest density.
$2$. Water and honey are liquids, which have a higher density than gases.
$3$. Cotton, chalk, and iron are solids, which have the highest density.
Within these categories, the specific order of increasing density is:
Air < Exhaust from chimneys < Cotton < Water < Honey < Chalk < Iron.