Hydraattisia

Hydraattisia is a term used in chemistry to describe compounds that contain water molecules incorporated into their crystal structure. These water molecules are known as water of hydration or sometimes just hydrate water. When a substance forms a hydrate, it typically occurs when an ionic compound crystallizes from an aqueous solution. The water molecules become bound to the ions through electrostatic interactions, forming a stable, organized structure.

The presence of water of hydration can significantly alter the physical properties of a substance compared to its anhydrous (water-free) form. For example, hydrates often have different colors, densities, and melting points. Some substances readily form hydrates, while others do not. The number of water molecules associated with each formula unit of the compound is indicated in its chemical formula, often by a dot followed by the number of water molecules, such as CuSO4·5H2O for copper(II) sulfate pentahydrate.

Heating a hydrate can cause the water of hydration to be driven off, a process called dehydration. This often results in a change in appearance, and the substance returns to its anhydrous state. The reversibility of hydration and dehydration is a key characteristic. Some hydrates can be rehydrated by exposure to moisture. The study of hydrates is important in various fields, including materials science, pharmaceuticals, and industrial processes where the water content of a solid can affect its behavior and usability.