Chemistry
Chemistry
Problem
A chemist stores 10.0 g of ethanol in three sealed, rigid containers maintained respectively at –120 °C, 25 °C, and 80 °C. At –120 °C the ethanol is a crystalline solid, at 25 °C it is a liquid, and at 80 °C it exists as a vapor at 1.00 atm. Assume no chemical decomposition occurs and that the mass of ethanol remains 10.0 g in each container. (a) Describe qualitatively how the average spacing between ethanol molecules differs among the three containers. (b) Rank the ethanol samples in order of decreasing mass density (largest to smallest). Justify your ranking in terms of molecular spacing. (c) Rank the three samples in order of increasing ease of compression (least pressure required to achieve a given fractional volume decrease). Explain your reasoning. (d) For each phase, discuss how the effective strength of intermolecular forces influences both the density and the compressibility you ranked above.Intuitive explanation
The key insight is that density changes dramatically across phase transitions, even though the mass stays constant. Since each container is rigid (fixed volume), the same 10.0 g of ethanol will occupy very different volumes depending on its physical state—solid, liquid, and gas have vastly different densities. Understanding how tightly molecules pack in each phase lets you rank the volumes and predict properties like pressure in the sealed containers.
Intuitive explanation
The key insight is that density changes dramatically across phase transitions, even though the mass stays constant. Since each container is rigid (fixed volume), the same 10.0 g of ethanol will occupy very different volumes depending on its physical state—solid, liquid, and gas have vastly different densities. Understanding how tightly molecules pack in each phase lets you rank the volumes and predict properties like pressure in the sealed containers.