Final answer:
When water changes from a solid to a gas phase without a liquid phase, it undergoes sublimation, which occurs under very low pressure for water and at standard atmospheric pressure for carbon dioxide (dry ice).
Step-by-step explanation:
Sublimation of Water and Other Substances
When water changes from a solid to a gas without becoming a liquid, there is no liquid phase. This process is called sublimation, and it occurs at pressures below 0.00600 atm for water. Sublimation can account for significant losses of snowpack as well as being utilized in technological applications such as the automatic defrosting of freezers and the freeze-drying of foods. Carbon dioxide, known as dry ice in its solid form, sublimates directly to gas at atmospheric pressure without passing through a liquid phase, unlike water which requires very low pressures to skip the liquid phase.
Sublimation demonstrates how pressure and temperature affect the states of matter, creating situations where conventional phase changes, like melting and evaporating, do not occur. At pressures below the triple point, water exists only as solid or gas and can undergo sublimation. Familiar examples of this include the disappearing of snow without melting or the evaporation of ice cubes in a freezer.