ANS:A - bound

Bound moisture refers to water molecules that are physically or chemically attached to the structure of a material, typically through mechanisms such as adsorption, absorption, or molecular interaction. Unlike free or unbound moisture, which can readily evaporate at a given temperature and pressure, bound moisture remains tightly associated with the material and does not contribute significantly to the material's vapor pressure. Here's a breakdown of the different types of bound moisture:

1. Adsorbed Moisture: Adsorbed moisture refers to water molecules that adhere to the surface of a material due to physical forces such as van der Waals interactions or hydrogen bonding. This type of moisture can be removed by heating or reducing the relative humidity of the surrounding environment.
2. Absorbed Moisture: Absorbed moisture refers to water molecules that have been absorbed into the internal structure of a material, such as porous materials like wood, paper, or textiles. The water molecules may be held within the pores or capillaries of the material through capillary action or chemical bonding.
3. Chemically Bound Moisture: Chemically bound moisture occurs when water molecules form chemical bonds with the molecules of the material itself. This type of moisture is more strongly bound and requires higher temperatures or specific chemical treatments to release.

Bound moisture is often considered separately from free moisture in materials because it behaves differently during processes such as drying, heating, or storage. Bound moisture typically requires higher temperatures or longer times to remove compared to free moisture. Understanding the presence and characteristics of bound moisture is important in various industries such as food processing, pharmaceuticals, construction, and materials science, as it can impact the properties, stability, and processing of materials.