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

Explanation

To arrange the substances in order of increasing density, we will first identify the approximate densities of each substance and then arrange them accordingly.

### Step 1: Identify the Densities
1. **Air**: Approximately 0.0012 g/cm³
2. **Exhaust from chimneys**: Slightly denser than air, approximately 0.0015 g/cm³ (depends on the composition, but generally lighter than most liquids).
3. **Cotton**: Approximately 0.3 g/cm³ (light solid, but denser than air and exhaust).
4. **Water**: Approximately 1 g/cm³ (common reference point for density).
5. **Honey**: Approximately 1.42 g/cm³ (thicker liquid than water).
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