A. At room temperature, the energy present in the water molecules is sufficient to overcome the inter-molecular forces of attraction that would be present in ice (solid phase), but not enough to get converted into the gaseous phase. Thus water exists as a liquid at room temperature.

B. Naphthalene balls undergo sublimation process in which the naphthalene balls (solid) are converted into their vapour state directly. Therefore, they disappear without leaving any solid behind. Naphthalene balls are commonly used to store clothes. They prevent the attack of moths or molds on the clothes or other materials.

C. The particles of perfume (gaseous state) mix with the air quickly. This process of intermixing on their own is called diffusion. The diffused particles move with high speeds due to weak inter-molecular forces of attraction and travel long distances (several metres). Hence we can smell the perfume from several meters away.