During a very cold winter, the temperature may remain below freezing for extended periods. However, fallen snow can still disappear, even though it cannot melt. This is possible because a solid can vaporize directly, without passing through the liquid state. Is this process (sublimation) a physical or a chemical change?

Sublimation is a physical change.

Explanation:

Phase changes such as evaporation, sublimation, condensation, deposition, etc are physical changes where only changes in the energy states of matter take place.

A change that occurs in the physical form or physical properties of a substance without altering its chemical composition i.e., chemical bonds are not broken or formed is known as a physical change. For example, when water (liquid) evaporates into water vapor (gas) or water (liquid) freezes to form ice (solid) or ice sublimes to form water vapor (gas), there are only changes in the physical form of water, but the chemical identity of the water is not altered (water remains water, no matter if it is solid, liquid or gas).

A change occurs when one or more substances react to form other substances by the breaking or making of some chemical bonds is known as a chemical change or chemical reaction. For example, the reaction between hydrochloric acid and sodium hydroxide produces salt (sodium chloride) and water.

Sublimation is a phase change where a substance transforms into the gas state from the solid-state without passing through the liquid state. It is an endothermic process where the molecules of a solid substance overcome the attractive forces of the neighboring molecules and escape into the vapor phase by the absorption of heat energy. It is only a physical change since the chemical composition of the substance is not altered. This process is usually used as a purification technique. Examples include the sublimation of snow and ice at temperatures below the freezing point during a very cold winter, sublimation is dry ice (solid carbon dioxide), etc.

a plasma is a warm ionized gasoline consisting of approximately equal numbers of definitely charged ions and negatively charged electrons. the characteristics of plasmas are notably unique from the ones of ordinary neutral gases in order that plasmas are considered a awesome "fourth kingdom of remember."