Solid water (ice) is slowly warmed from a very low temperature. What minimum external pressure $p_1$ must be applied to the solid if a melting phase transition is to be observed? Describe the sequence of phase transitions that occur if the applied pressure $p$ is such that .

The vapor pressure is the pressure of the vapor phase of a substance when it is in equilibrium with the solid or liquid phase of the substance. The relative humidity is the partial pressure of water vapor in the air divided by the vapor pressure of water at that same temperature, expressed as a percentage. The air is saturated when the humidity is $100\%$. The vapor pressure of water at $20.0$°C is $2.34\times {10}^3$ Pa. If the air temperature is $20.0$°C and the relative humidity is $60\%$, what is the partial pressure of water vapor in the atmosphere (that is, the pressure due to water vapor alone)?

For diatomic carbon dioxide gas (CO₂, molar mass $44.0$ g/mol) at $T = 300$ K, calculate the average speed $v_{av}$.

For a gas of nitrogen molecules (N₂), what must the temperature be if $94.7\%$ of all the molecules have speeds less than $1500$ m/s? Use Table $18.2$. The molar mass of N₂ is $28.0$ g/mol.

For diatomic carbon dioxide gas (CO₂, molar mass $44.0$ g/mol) at $T=300$ K, calculate the root-mean-square speed $v_{rms}$.