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Ch 18: A Macroscopic Description of Matter
Chapter 18, Problem 18

How many atoms are in a 2.0 cm×2.0 cm×2.0 cm cube of aluminum?

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Determine the volume of the aluminum cube using the formula for the volume of a cube, V = a^3, where 'a' is the length of a side of the cube.
Convert the volume from cubic centimeters to cubic meters by using the conversion factor (1 m = 100 cm).
Calculate the mass of the aluminum cube using the density formula, \( \rho = \frac{m}{V} \), where \( \rho \) is the density of aluminum (approximately 2700 kg/m^3). Rearrange the formula to find the mass (m = \( \rho \times V \)).
Use Avogadro's number and the molar mass of aluminum to find the number of moles of aluminum in the cube. The molar mass of aluminum is approximately 26.98 g/mol.
Multiply the number of moles by Avogadro's number (approximately 6.022 \times 10^{23} atoms/mol) to find the total number of aluminum atoms in the cube.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Structure

Atoms are the basic building blocks of matter, consisting of protons, neutrons, and electrons. In a solid like aluminum, atoms are arranged in a closely packed structure, which influences the material's properties. Understanding atomic structure is essential for calculating the number of atoms in a given volume.
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Density

Density is defined as mass per unit volume and is a critical property for determining how many atoms are present in a specific volume of material. For aluminum, the density is approximately 2.7 g/cm³. By knowing the density, one can calculate the mass of the aluminum cube and subsequently the number of atoms it contains.
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Avogadro's Number

Avogadro's number, approximately 6.022 x 10²³, is the number of atoms or molecules in one mole of a substance. This concept is vital for converting the mass of aluminum into moles and then determining the total number of atoms. It provides a bridge between macroscopic measurements and atomic-scale quantities.
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