Solution:
The above statement is true.On heating, most solid substances change to liquid and then convert into a gaseous state on further heating. Similarly, cooling a gaseous substance is first converted into liquid and then a solid. But some solid substances on heating are directly converted into a gaseous state without passing through the liquid phase. Similarly, on cooling, the vapours are directly converted into a solid. Such substances are called sublimate, and the process is called sublimation. The naphthalene balls undergo sublimation. The naphthalene is kept between woollen and silk clothes to protect them from insects and moths. After some time, these balls do not leave any residue behind. The naphthalene balls sublime, and the vapours thus formed prevent the clothes from insects and moths.
