Final answer:
A 1g piece of aluminum with a density of 2.70 g/cm³ will sink when dropped into water because its density is greater than the density of water, resulting in the aluminum being pulled to the bottom by gravity.
Step-by-step explanation:
If a 1g piece of aluminum is dropped in a cup of water, with aluminum having a density of 2.70 g/cm³ and water having a density of 1.00 g/cm³, the aluminum will sink to the bottom. This occurs because the density of aluminum is higher than that of water, indicating that for a given volume, aluminum has more mass than water. Therefore, buoyant forces cannot keep it afloat, and gravity will pull it downwards.
Density is a measure of how much mass is contained in a given volume. From our understanding that the density of aluminum is approximately 2.7 times that of water, we can infer that any piece of aluminum, irrespective of its mass, will be denser than water. This clearly supports the outcome that a piece of aluminum will sink when placed in water due to the simple fact that its density is greater than water's density.