Final answer:
Lead is the most dense substance in the provided list, with a higher density than aluminum, iron, and wood, due to its heavy atoms and close atomic packing.
Step-by-step explanation:
The substance that is the most dense in the provided list is lead (Pb). When comparing the densities of different substances, it is important to refer to their specific density values. From the information provided, we know that the density of aluminum is 2.7 g/cm³ and that the density of iron is higher than that of wood and air, implying it is more than 2.7 g/cm³. However, no direct density value is provided for lead within the information.
Nevertheless, it is commonly known that lead is denser than both aluminum and iron due to its heavy atoms and close atomic packing. In summary, among aluminum, iron, wood, and lead, lead has the highest density. This is consistent with general scientific knowledge, as the densities of solids like lead are much higher than those of other phases, such as gases, due to the close packing of atoms and significantly less empty space between them.