Use the volumes found by displacement to calculate the densities of the objects. Record your data in Table 2.2. The accepted values for density are: aluminum = 2.71 g/cm3; PE = about 0.925 g/cm3; and iron = 7.87 g/cm3. Compare your values from Question 4 with these. How do they compare? Why are they different? Note: the density of different kinds of PE and PVC vary because of the difference in the arrangements of their molecules.