Chapter 6

A needle sinks when placed on the surface of hot \(\left(90^{\circ} \mathrm{C}\right)\) water but floats when placed on the surface of cold \(\left(5^{\circ} \mathrm{C}\right)\) water. Why?

The mercury level in a capillary tube inserted into a dish of mercury is below the surface of the mercury in the dish. Why?

Describe the origin of surface tension in terms of inter molecular interactions.

Why does the density of water increase when it is cooled from \(6^{\circ} \mathrm{C}\) to \(4^{\circ} \mathrm{C}\) but then increase when it is cooled from \(4^{\circ} \mathrm{C}\) to \(2^{\circ} \mathrm{C} ?\)

Which type of inter molecular force exists in all substances?

Why does water climb higher in a capillary tube than in a test tube?

Methanol has a larger molar mass than water but boils at a lower temperature. Suggest a reason why.

What kinds of intermolecular forces must be overcome as (a) solid \(\mathrm{CO}_{2}\) sublimes; (b) \(\mathrm{CHCl}_{3}\) boils; (c) ice melts?

Which of these compounds has the lowest boiling point: (a) \(\mathrm{CH}_{4},\) (b) \(\mathrm{CH}_{3} \mathrm{Cl},(\mathrm{c}) \mathrm{CH}_{2} \mathrm{Cl}_{2},\) (d) \(\mathrm{CHCl}_{3},\) (e) \(\mathrm{CCl}_{4}.\)

A partially filled bottle contains an equal number of moles of methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right),\) ethanol \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right),\) and propanol \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\right) .\) Which of these alcohols is present in the highest mole percent in the vapor above the liquid mixture in the bottle?

Does the sublimation point of ice increase or decrease with increasing pressure?

Why is methanol miscible with water but methane is not?

The melting point of hydrogen is \(15.0 \mathrm{K}\) at 1.00 atm. The temperature of its triple point is \(13.8 \mathrm{K} .\) Does liquid \(\mathrm{H}_{2}\) expand or contract when it freezes?

Sketch a phase diagram for element \(Z\), which has a triple point at \(152 \mathrm{K}\) and 0.371 atm, a boiling point of \(166 \mathrm{K}\) at a pressure of 1.00 bar, and a normal melting point of \(161 \mathrm{K}.\)