Name the phase transition in each of the following situations and indicate whether it is exothermic or endothermic: (d) Molten lava from a volcano turns into solid rock.

Ethyl chloride (C₂H₅Cl) boils at 12 °C. When liquid C₂H₅Cl under pressure is sprayed on a room-temperature (25 °C) surface in air, the surface is cooled considerably. (a) What does this observation tell us about the specific heat of C₂H₅Cl(g) as compared with that of C₂H₅Cl(l)?

Ethyl chloride (C₂H₅Cl) boils at 12 °C. When liquid C₂H₅Cl under pressure is sprayed on a room-temperature (25 °C) surface in air, the surface is cooled considerably. (b) Assume that the heat lost by the surface is gained by ethyl chloride. What enthalpies must you consider if you were to calculate the final temperature of the surface?

For many years drinking water has been cooled in hot climates by evaporating it from the surfaces of canvas bags or porous clay pots. How many grams of water can be cooled from 35 to 20 °C by the evaporation of 60 g of water? (The heat of vaporization of water in this temperature range is 2.4 kJ/g. The specific heat of water is 4.18 J/g-K).

The critical temperatures and pressures of a series of halogenated methanes are as follows:

(a) List the intermolecular forces that occur for each compound.

The critical temperatures and pressures of a series of halogenated methanes are as follows: (c) Predict the critical temperature and pressure for CCl4 based on the trends in this table. Look up the experimentally determined critical temperatures and pressures for CCl4, using a source such as the CRC Handbook of Chemistry and Physics, and suggest a reason for any discrepancies.

(a) Place the following substances in order of increasing volatility: CH₄, CBr₄, CH₂Cl₂, CH₃Cl, CHBr₃, and CH₂Br₂. (b) How do the boiling points vary through this series? (c) Explain your answer to part (b) in terms of intermolecular forces.

(a) Two pans of water are on different burners of a stove. One pan of water is boiling vigorously, while the other is boiling gently. What can be said about the temperature of the water in the two pans?

You are high up in the mountains and boil water to make some tea. However, when you drink your tea, it is not as hot as it should be. You try again and again, but the water is just not hot enough to make a hot cup of tea. Which is the best explanation for this result? (a) High in the mountains, it is probably very dry, and so the water is rapidly evaporating from your cup and cooling it. (b) High in the mountains, it is probably very windy, and so the water is rapidly evaporating from your cup and cooling it. (c) High in the mountains, the air pressure is significantly less than 1 atm, so the boiling point of water is much lower than at sea level. (d) High in the mountains, the air pressure is significantly less than 1 atm, so the boiling point of water is much higher than at sea level.

Using the vapor-pressure curves in Figure 11.25, (d) estimate the external pressure at which diethyl ether will boil at 40 °C.

Appendix B lists the vapor pressure of water at various external pressures. (c) A city at an altitude of 5000 ft above sea level has a barometric pressure of 633 torr. To what temperature would you have to heat water to boil it in this city?

Referring to Figure 11.29, describe the phase changes (and the temperatures at which they occur) when CO2 is heated from -80 to -20°C at (a) a constant pressure of 3 atm,

The phase diagram for neon is

Use the phase diagram to answer the following questions. (a) What is the approximate value of the normal melting point?

Use the phase diagram of neon to answer the following questions. (a) What is the approximate value of the normal boiling point?

Use the phase diagram of neon to answer the following questions. (b) What can you say about the strength of the intermolecular forces in neon and argon based on the critical points of Ne and Ar (see Table 11.5.)?

At 25 °C gallium is a solid with a density of 5.91 g/cm³. Its melting point, 29.8 °C, is low enough that you can melt it by holding it in your hand. The density of liquid gallium just above the melting point is 6.1 g/cm³. Based on this information, what unusual feature would you expect to find in the phase diagram of gallium?

Indicate whether each statement is true or false: (a) The liquid crystal state is another phase of matter, just like solid, liquid, and gas. (b) Liquid crystalline molecules are generally spherical in shape. (d) Molecules that exhibit a liquid crystalline phase show weaker-than-expected intermolecular forces. (e) Molecules containing only carbon and hydrogen are likely to form liquid crystalline phases. (f) Molecules can exhibit more than one liquid crystalline phase.