Here's why:
* Kinetic Energy: As temperature rises, molecules gain more kinetic energy. This increased movement makes it easier for solute molecules to break apart from each other and disperse among the solvent molecules.
* Enthalpy of Dissolution: The process of dissolving a solid in a liquid often requires energy (endothermic). Increasing the temperature provides this energy, making it easier for the dissolution to occur.
However, there are some exceptions:
* Gases: The solubility of gases in liquids *decreases* as temperature increases. Think about a carbonated beverage: it goes flat as it warms up because the CO2 gas is less soluble in the liquid.
* Certain Salts: A few salts, like lithium sulfate (Li₂SO₄), become *less* soluble as the temperature increases.
In general, the solubility of solids and liquids in liquids increases with increasing temperature.
