Argon has a normal boiling point of 87.2 K and a melting...

Name: Problem 74, Chapter 11: Chemistry: Structure and Properties
Uploaded: 2021-08-26T00:10:01-08:00
Duration: 3 min 35 s
Channel: Lori Mccoy
Description: Argon has a normal boiling point of 87.2 K and a melting point (at 1 atm) of 84.1 K. Its critical temperature is 150.8 K, and its critical pressure is 48.3 atm. It has a triple point at 83.7 K and 0.68 atm. Sketch the phase diagram for argon. Which has the greater density, solid argon or liquid argon?

Argon has a normal boiling point of 87.2 K and a melting point (at 1 atm) of 84.1 K. Its critical temperature is 150.8 K, and its critical pressure is 48.3 atm. It has a triple point at 83.7 K and 0.68 atm. Sketch the phase diagram for argon. Which has the greater density, solid argon or liquid argon?

Key Concepts

Phase Diagram

A phase diagram is a graphical representation of the conditions of temperature and pressure at which distinct phases (solid, liquid, and gas) of a substance exist in equilibrium. It includes boundaries that indicate where phase transitions occur, such as melting, boiling, and sublimation curves, and highlights special points like the triple point and critical point.

Triple Point

The triple point on a phase diagram is the unique set of conditions where all three phases of a substance (solid, liquid, and gas) coexist in equilibrium. It is a critical reference point that defines the fundamental thermodynamic properties of the substance.

Critical Point

The critical point marks the end of the liquid-gas coexistence curve on a phase diagram. Beyond this point, the liquid and gas phases become indistinguishable, forming a supercritical fluid with unique properties.

Melting and Boiling Points

Melting and boiling points are specific temperatures at which a substance changes phase at a given pressure, typically one atmosphere. The melting point is where a solid becomes a liquid, and the boiling point (or normal boiling point) is where a liquid becomes a gas. These transition points are key markers on the phase diagram.

Density Differences in Phase Transitions

Density variations between different phases of a substance are an important aspect of phase behavior. For most substances, including noble gases like argon, the solid phase is denser than the liquid phase because the molecules are packed more closely together. This contrasts with anomalous substances like water, where the solid phase is less dense than the liquid phase.

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