Is the process of moth balls gradually dissapearing in a closet a physical or chemical change?
It is a physical change called sublimation. Whereas most solids on being heated first become liquids and only vaporise (evaporate), i.e. turn into gas on heating to higher temperatures, there are some solids like sulphur or naphthalene (the material in moth balls) that directly go on heating from solid to gas, i.e. they sublime.
