2 Classification of Matter Solutions are homogeneous mixtures
3 Solute Solvent A solute is the dissolved substance in a solution. Salt in salt waterSugar in soda drinksCarbon dioxide in soda drinksSolventA solvent is the dissolving medium in a solution.Water in salt waterWater in soda
4 SolubilityIf less than one gram of the substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered insoluble.If more than ten grams of substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered soluble.If between one and ten grams of a substance will dissolve in 100 grams (or 100 mL) of solvent, the substance is considered moderately soluble.
5 “Like Dissolves Like”Nonpolar solutes dissolve best in nonpolar solventsFatsBenzeneSteroidsHexaneWaxesToluenePolar and ionic solutes dissolve best in polar solventsInorganic SaltsWaterSugarsSmall alcoholsAcetic acid
6 Solubility of Ionic Compounds in Water The polar charges on water molecules are attracted to the opposite charge on the ions in ionic compoundsIf this attraction causes the ions to separate (“dissociate”), then the ionic compound “dissolves”Ionic compounds that are soluble, always form ions in solution
9 Electrolytes and Nonelectrolytes An electrolyte is:A substance whose aqueous solution conducts an electric currentIonic compounds form electrolytes when they dissolve, because the ions separate and move around independentlyA nonelectrolyte is:A substance whose aqueous solution does not conduct an electric currentMolecular compounds do not form electrolytes when they dissolve
11 Solubility of Molecular Compounds in Water •If we are comparing the water solubility of two similar molecules, the one with the higher percentage of the molecule that is polar (hydrophilic) is expected to have higher water solubility.•We predict that the molecule with the higher percentage of its structure that is nonpolar (hydrophobic) to be less soluble in water.
21 Solubility TrendsThe solubility of MOST solids increases with temperature.The rate at which solids dissolve increases with increasing surface area of the solid.The solubility of gases decreases with increases in temperature.The solubility of gases increases with the pressure above the solution.
23 Solubility and Temperature Temperature affects how much solute dissolves (solubility)Temperature affects how quickly a solute dissolves (rate)Increasing the temperature not only increases the amount of solute that will dissolve but also increases the rate at which the solute will dissolve
24 Therefore… Solids tend to dissolve best when: Heated Stirred Ground into small particlesGases tend to dissolve best when:The solution is coldPressure is high