Referring to the phase diagram for carbon dioxide shown in...

Referring to the phase diagram for carbon dioxide shown in Active Figure $13-17 \mathrm{~b}$ for approximate values, draw a heating curve similar to that in Active Figure $13-15$ for carbon dioxide at 1 atmosphere pressure. Draw a second heating curve for carbon dioxide at 5 atm pressure. Estimate the transition temperatures.

Key Concepts

Pressure Effects on Phase Behavior

Pressure significantly influences the temperatures and conditions at which phase transitions occur. Higher pressures can shift phase transition temperatures, such as increasing the boiling point or enabling states that are not under lower pressures. Understanding this dependence is critical when analyzing phase diagrams and heating curves under different pressure constraints.

Phase Transitions

Phase transitions refer to the processes wherein a substance changes from one state of matter to another—such as from solid to liquid (melting), liquid to gas (boiling), or solid directly to gas (sublimation). These transitions occur at specific temperatures and pressures, during which the temperature remains constant as energy is used to alter the internal bonding rather than increasing kinetic energy.

Heating Curves

A heating curve illustrates the change in temperature of a substance as heat is added, marking the regions where the temperature remains constant during phase transitions despite the continuous input of heat. It demonstrates the energy absorbed as latent heat to change the state of the material, separating regions of temperature rise (sensible heat) from phase change plateaus.

Phase Diagrams

A phase diagram is a graphical representation that maps the regions of stability for different phases of a substance as functions of temperature and pressure. It shows the conditions under which a substance exists as a solid, liquid, or gas, and depicts boundaries where phase transitions occur. This tool is essential for understanding the equilibrium states of materials and predicting behavior under varying thermodynamic conditions.

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