1. Solvation:
* Water molecules approach the surface of the solid: Water molecules, being polar, have a positive end (hydrogen) and a negative end (oxygen). These poles create attractive forces with the ions or molecules in the crystalline solid.
* Water molecules surround the ions or molecules: The positive end of water molecules will interact with negatively charged ions or molecules in the solid, while the negative end will interact with positively charged ions or molecules. This process is called solvation.
* The attractive forces between water molecules and the solid particles overcome the forces holding the solid together: As more water molecules surround the particles, the attractions between the water molecules and the solid particles become stronger than the attractions holding the particles together in the crystal lattice.
2. Dissociation:
* Ionic compounds: If the solid is an ionic compound, the water molecules pull the ions apart, separating them from the crystal lattice. This process is called dissociation. The ions are now surrounded by water molecules, forming a hydrated ion.
* Covalent compounds: If the solid is a covalent compound, the water molecules may still surround the molecules, breaking the intermolecular forces holding the solid together. This process is called solvation.
3. Formation of a Solution:
* The separated particles are now dispersed evenly throughout the water: The dissolved ions or molecules are now evenly distributed throughout the water, forming a homogeneous mixture called a solution.
Factors Affecting Dissolution:
* Nature of the solute and solvent: Polar solutes (like ionic compounds) dissolve well in polar solvents like water, while nonpolar solutes dissolve well in nonpolar solvents.
* Temperature: Increasing temperature generally increases the rate of dissolution.
* Pressure: For gases dissolving in liquids, increasing pressure increases the solubility.
* Surface area of the solid: A larger surface area allows more contact points for water molecules to interact with the solid, increasing the rate of dissolution.
Key takeaways:
* Dissolution is a physical process where the attractive forces between water molecules and the solid particles overcome the forces holding the solid together.
* Water molecules surround and solvate the particles, separating them from the crystal lattice.
* The result is a homogeneous mixture called a solution.
