Final answer:
The student's question calculating the density of a solid (21 g and 2 cm³) found it to be 10.5 g/cm³. This does not match common substances' densities directly, indicating the need for further investigation or data.
Step-by-step explanation:
The question asks for the identification of a substance based on its mass and volume. We will use the property of density to determine which substance the sample could be. Density is the mass of a substance per unit volume (mass divided by volume). To find the density of the solid, we use the formula: Density = Mass / Volume. Given that the mass of the solid is 21 g and the volume is 2 cm³, we calculate the density as follows:
Density = 21 g / 2 cm³ = 10.5 g/cm³
Comparing this value to a list of known densities, such as the ones provided for aluminum and gold, we can determine which substance the sample is likely to be. Since the calculated density does not exactly match the density of a common substance in the list, we may need to consider that this could be an alloy or a material with impurities, and further investigation or additional data would be necessary to conclusively identify the substance.