b. Why does this phenomenon not take place between two solids?
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Answer:
When materials in a solid move directly into the gaseous state, it’s called Sublimation. Most solids can do this to varying degrees. Water is extremely good at this process, and this plays a significant role in our weather. This because the ice absorbs heat energy during sublimation. Here is what Wakipedia has to say:
Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.[1] Sublimation is an endothermic process that occurs at temperatures and pressures below a substance's triple point in its phase diagram. The reverse process of sublimation is deposition or desublimation, in which a substance passes directly from a gas to a solid phase.[2] Sublimation has also been used as a generic term to describe a solid-to-gas transition (sublimation) followed by a gas-to-solid transition (deposition).[3]
At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gaseous state requires an intermediate liquid state. The pressure referred to is the partial pressure of the substance, not the total (e.g. atmospheric) pressure of the entire system. So, all solids that possess an appreciable vapour pressure at a certain temperature usually can sublime in air (e.g. water ice just below 0 °C). For some substances, such as carbon and arsenic, sublimation is much easier than evaporation from the melt, because the pressure of their triple point is very high, and it is difficult to obtain them as liquids.
The term sublimation refers to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction. Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen.
Sublimation requires additional energy and is an endothermic change. The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization.
Other good examples are CO2(s) which is dry ice, and Naphthalene(s) which is moth balls.
Answer:
because their intermolecular force is very tight