Formations of Solutions Objectives: 1.Explain the process by which solutions form. 2.Give the definition of solubility and explain how it is affected by variousfactors. KeyTerms: Solvation, hydration, solubility

Solutions Solutions are homogenous (looks the same) mixtures of substances in a single state. – Solutions can exist in any phase – The particles in a solution are very small - atoms, ions,molecules – Particles in a solution are evenly distributed – one part of the solution has the same molecular make-up as another – Solutions do not separate under normal conditions Common solution types: – alloy - solution consisting of 2 or more metals – aqueous - any solution containing water – hydrate - solution where water is the solvent

Solvation Solvation is the term given to the interaction between solvent and solute. – If the solvent is water the reaction is called hydration - water is the most common polar solvent solute - substance dissolved in a solution solvent - substance that does the dissolving soluble - substance that is capable of dissolving – Remember that “like dissolves like”… polar and ionic solutes dissolve in polar solvents and non-polar solutes in non-polar solvents insoluble - substance that does not dissolve miscible – soluble in any amount

Solubility Solubility is the amount of solute that can dissolve in a solution at given conditions. – expressed in grams of solute per 100grams of solvent. – A solvent containing its maximum amount of solute is said to be saturated with solute any amount less is unsaturated holding more solute (past saturation point) is supersaturated – Created by cooling a saturated solution – substances that can mix in any proportions are said to be miscible example: alcohol and water solvent is substance with the greater amount Substances that don't mix in any proportion are said to be immiscible – example: oil & water

Factors Affecting Solubility - Temperature Temperature – Solubility of a gas is decreased with an increase in temperature due to an increase in the kinetic energy of the molecules vapor pressure of the gas rises – Solubility of a solid is usually increased with an increase in temperature by increasing the KE of the solution exception: – Exothermic rxns (reactions releasing heat) - increasing temperature decreases solubility – an increase temperature has no effect on solubility when there is no temperature change for the solution (boiling)

Factors Affecting Solubility - Pressure Pressure – Solubility of a gas is increased with and increase in pressure (Henry's Law) S 1 /P 1 = S 2 /P 2 Solubility of a gas is directly proportional to the pressure exerted above it – Solubility of a solid is usually unaffected by pressure

Factors Affecting Solubility – Solute Size Surface area – The greater the surface area the greater the rate of dissolving – Breaking the solute into smaller pieces increases the surface area Greater Surface Area

Factors Affecting Solubility – Stirring Stirring - increases the rate of dissolving by bringing solvent in contact with solute