The phenomenon you're describing, where the size of naphthalene balls reduces over time when placed in an open environment, is known as sublimation. Naphthalene is a solid compound that can undergo sublimation, which means it transitions directly from a solid to a gaseous state without passing through a liquid phase. Here's an explanation of why this occurs:
Sublimation process: Naphthalene has a relatively high vapor pressure, even at room temperature. Vapor pressure refers to the tendency of a substance to evaporate and become a gas. When naphthalene balls are exposed to air, the molecules on the surface gain enough energy to break free from the solid state and enter the gaseous phase directly.
Gradual evaporation: As the naphthalene molecules evaporate into the air, the size of the naphthalene balls decreases over time. The process is similar to how an ice cube slowly shrinks as it sits in a freezer, even without direct melting.
Open environment: Placing naphthalene balls in an open environment provides a continuous exchange of air, allowing for a consistent supply of fresh air molecules to interact with the naphthalene's surface. This continuous exposure promotes the sublimation process and the gradual reduction in size of the naphthalene balls.
It's worth noting that sublimation is influenced by various factors such as temperature, air circulation, and the surface area of the substance. Higher temperatures and increased air movement can accelerate the sublimation process. So, in warmer environments with good airflow, naphthalene balls may sublimate more quickly.
Sublimation of naphthalene balls is a natural process and does not pose any significant health risks. However, it's advisable to use naphthalene balls in well-ventilated areas to avoid inhaling the vaporized particles and to prevent prolonged exposure to concentrated levels of the substance.