Passage
Water is unique in that all three of its phases exist over a small range of pressures and temperatures, as shown in Figure 1.
Figure 1 Phase diagram for waterIn the liquid phase, water dissolves and transports molecules, and aids in the biochemical reactions necessary to support life. For this reason, scientists believe liquid-phase water is essential to the existence of extraterrestrial life. Although it has been known for some time that water is present in both the gas and ice phases on Mars, the question remains as to whether there are regions where liquid-phase water can stably exist. Estimates of Mars' surface temperature and pressure generated from satellite readings and global climate models, as well as observations made by Mars rovers, reveal that surface conditions on the planet can vary greatly.Table 1 Temperature and Pressure of Various Locations on Mars
Despite the extremely low pressures and temperatures on Mars, satellite images have repeatedly found evidence of flowing liquid water in several regions during the late Martian summer season. These regions, called recurring slope lineae (RSL) , are hypothesized to be thermodynamically stable under certain Martian conditions due to the presence of dissolved salts. A simple understanding of this hypothesis is afforded by Raoult law, which states that the vapor pressure and freezing point of an ideal solution are lowered as the number of moles of dissolved solute increases. Moreover, this effect also impacts the solution boiling point (the point at which the vapor pressure of the solution becomes equal to the ambient pressure) .The briny-water hypothesis was confirmed in 2015 when spectral data from the Compact Reconnaissance Imaging Spectrometer onboard the Mars Reconnaissance Orbiter revealed the presence of hydrated perchlorates in the same regions and times that RSL were observed. Studies are already underway to determine how common such briny water flows are and whether the conditions within them are suitable for microbial life.
-Which of the following conclusions can be made based on Figure 1 and the data in Table 1?

Question

Passage
Water is unique in that all three of its phases exist over a small range of pressures and temperatures, as shown in Figure 1.

Figure 1 Phase diagram for waterIn the liquid phase, water dissolves and transports molecules, and aids in the biochemical reactions necessary to support life. For this reason, scientists believe liquid-phase water is essential to the existence of extraterrestrial life. Although it has been known for some time that water is present in both the gas and ice phases on Mars, the question remains as to whether there are regions where liquid-phase water can stably exist. Estimates of Mars' surface temperature and pressure generated from satellite readings and global climate models, as well as observations made by Mars rovers, reveal that surface conditions on the planet can vary greatly.Table 1 Temperature and Pressure of Various Locations on Mars

Despite the extremely low pressures and temperatures on Mars, satellite images have repeatedly found evidence of flowing liquid water in several regions during the late Martian summer season. These regions, called recurring slope lineae (RSL) , are hypothesized to be thermodynamically stable under certain Martian conditions due to the presence of dissolved salts. A simple understanding of this hypothesis is afforded by Raoult law, which states that the vapor pressure and freezing point of an ideal solution are lowered as the number of moles of dissolved solute increases. Moreover, this effect also impacts the solution boiling point (the point at which the vapor pressure of the solution becomes equal to the ambient pressure) .The briny-water hypothesis was confirmed in 2015 when spectral data from the Compact Reconnaissance Imaging Spectrometer onboard the Mars Reconnaissance Orbiter revealed the presence of hydrated perchlorates in the same regions and times that RSL were observed. Studies are already underway to determine how common such briny water flows are and whether the conditions within them are suitable for microbial life.
-Which of the following conclusions can be made based on Figure 1 and the data in Table 1?

Quizplus · Accepted Answer

11ecba2d_11a3_e100_a3bf_e178264790f9_MD0008_00 A phase diagram illustrates a substance's stability in a given phase (solid, liquid, or gas) as a function of pressure and temperature. The triple point is the point at which all three boundary lines intersect, and indicates the temperature and pressure at which all three phases simultaneously exist in equilibrium. Liquid water cannot exist at pressures below the triple point. The boundary lines between phases indicate the conditions under which two phases are in equilibrium. If a change in conditions results in the crossing of a boundary line, a substance will undergo the corresponding change in phase. Liquid water initially at 274 K and 6.5 mb will cross the liquid-gas boundary line when heated to 313 K (the temperature at the Spirit location), so liquid water will boil under these conditions. (Choice A) Conditions at the Viking I location are 256 K and 7.11 mb. Under these conditions, water enters the solid phase. (Choice B) Sublimation can occur only at pressures below the triple point. Because 6.60 mb (the pressure at the Pathfinder site) is above the triple point, the ice will melt when heated to 274 K. (Choice C) Because 6.00 mb (Mars' average pressure) is below the triple point, liquid water cannot exist under these conditions. Therefore, exposing the vapor to average Martian atmospheric conditions will cause it to undergo a phase transition directly to ice (deposition). Educational objective: A phase diagram shows the stability of each phase (solid, liquid, and gas) as a function of pressure and temperature. Equilibrium between two phases is indicated by phase boundaries, and crossing a phase boundary indicates a phase change. The triple point is the temperature and pressure at which all three phases exist in equilibrium.

Passage Water Is Unique in That All Three of Its Phases