SOLUTIONS Sections 8.1 & 8.2

SOLUTIONS Solute—A substance whose particles are dissolved in a solution Solvent—The substance in which the solute dissolves The solution takes the state of the solvent

Solute Solvent Example Gas Air Liquid Water in air Carbonated beverages Vinegar Solid Sugar water Stainless steel

Substances can dissolve in water in three ways: Dissociation—An ionic compound separates into ions as it dissolves Dispersion—The process involves breaking into smaller pieces Ionization—Neutral molecules gain or lose electrons

PROPERTIES OF LIQUID SOLUTIONS The three physical properties of a solution that vary from those of its solute and solvent are: Conductivity Freezing point Boiling point

SOLUTIONS During the formation of a solution, energy is either released or absorbed (exothermic OR endothermic)

FACTORS AFFECTING RATES OF DISSOLVING Surface area —The greater the surface area, the more frequent the collisions occur which results in faster dissolving Stirring —Stirring the solution allows for more collisions Increasing temperature —increasing the temperature causes the particles in the solvent to move faster, thus there are more collisions

SOLUBILITY AND CONCENTRATION Solubility is the maximum amount of solute that dissolves in a given amount of solvent and a constant temperature

Three types of solutions Saturated solutions hold as much solute as the solvent can hold at a given temperature Unsaturated solutions have less than the maximum amount of solute that can be dissolved Supersaturated solutions contain more solute than it normally hold at a given temperature

Solubility curve Which substance does not greatly increase, increases the most, decrease in solubility, as the temp is increased? If 50g of KCl are dissolved in 100g of water at 50oC, what type of soln is formed? Which substance is the Most, Least soluble at 0oC? Which 2 substances have the same solubility at 60oC? At 30oC which substance, Pb(NO3)2 or KNO3, can form the more concentrated solution?

Solubility curve

FACTORS AFFECTING SOLUBILITY Polarity of the solvent— “LIKE DISSOLVES LIKE” meaning that a polar solvent will dissolve a polar solute Temperature—Temperature increases the solubility of a solid in a liquid but a gas becomes less soluble at higher temperatures Pressure—Increasing the pressure on a gas increases its solubility in a liquid

Concentration The concentration of a solution is the amount of solute dissolved in a specific amount of solution Concentration = Solute x 100% Solution

Concentration of solutions % by volume = Volume of solute x100% Volume of solution Percent by Mass=Mass of solute x 100% Mass of solution

Examples What is the concentration if: solute = 15mL and solution = 100mL? A 300 mL solution contains 50mL of HCl dissolved in 250mL of water. What is the concentration of the HCl? What is the concentration of water? The relative humidity is 30%. If you sample 1 liter of this air how much of it is water vapor and how much of it is air?