Answer: Sublimation.
Notes: A change in which one or more new substances are formed is called a chemical change. A chemical change is also called a chemical reaction. Chemical changes are very important in our lives. All new substances are formed as a result of chemical changes. For example, digestion of food in our body, ripening of fruits, fermentation of grapes, etc., happen due to series of chemical changes. A change in which a substance undergoes a change in its physical properties is called a physical change.. During sublimation, a solid substance when heated changes into vapour form, and the vapour on cooling gives back the substance in solid form.
