The Polarity of Water Molecules
Water is called a universal solvent because its molecules are polar, with oxygen being more electronegative than hydrogen, creating a partial negative charge near oxygen and partial positive charges near hydrogens. This polarity enables water to interact with and surround charged or polar solute particles, facilitating dissolution through the formation of hydration shells.
Hydrogen Bonding and Solvation
Key to water's solvent properties are hydrogen bonds, where the partially positive hydrogen of one water molecule attracts the partially negative oxygen of another. In solvation, these bonds allow water to stabilize ions or molecules by surrounding them, breaking down solute lattices like in ionic compounds such as sodium chloride, where Na+ and Cl- ions become individually hydrated.
Practical Example: Dissolving Table Salt
Consider table salt (NaCl) in water: the polar water molecules orient their negative ends toward Na+ ions and positive ends toward Cl- ions, weakening the ionic bonds in the salt crystal. This process, known as dissociation, results in a solution where ions are freely mobile, illustrating water's ability to dissolve both ionic and polar covalent substances like glucose.
Importance in Chemical and Biological Systems
Water's solvent capabilities are essential for life, enabling nutrient transport in cells, chemical reactions in aqueous environments, and metabolic processes. In chemistry, it supports reactions in solutions, pH regulation, and industrial applications like purification, underscoring its role in maintaining homeostasis and facilitating diverse biochemical interactions.