24.1 – How Solutions Form

 Same composition, color, density and taste throughout  Homogenous mixture  Exist in all states of matter  The air we breathe  Sterling silver  Brass  Alloys

 Solute = Substance being dissolved  Solvent = Substance doing the dissolving  You add a solute to a solvent  Solvents and Solutions exist in the same state of matter  Aqueous solution = solution with water as the solvent

 Dissolving occurs at the surface  Particles are always moving  Water molecules are polar  They have a positive and a negative end

 Water molecules clusters around the solid molecules with their negative ends attracted to the positive ends of the solids

 Liquids and gases follow the same procedure  Solids dissolved in solids  melt solid into liquid form then dissolve

 Rates vary by substances  Four ways to speed up dissolving 1. Stir the solution 2. Increase temperature 3. Increase pressure 4. Reduce the crystal size

 Surface area – breaking a solid into pieces or a powder increases surface area  Dissolving takes place at the surface  So more surface area allows for more solvent to come in contact with solute

 The amount of a substance that can dissolve in a solvent  Depends on the nature of substances  The solubility of two substances can be compared by measuring

 Expressed as a percent by volume of a solvent  A concentrated solution has a large amount of solute in the solvent  A dilute solution has a small amount of solute in the solvent

 Saturated solution  Contains all the solute it can hold at a given temperature  As temperature of a liquid solvent increases, the amount of solid solute it can dissolve increase  Unsaturated solution  Able to dissolve more solute at a given temperature

 Solubility curve  Line on a graph used to figure how much solute can dissolve at any temperature on the graph

 Supersaturated solution  Contains more solute than a saturated one at the same temperature  Made by raising temperature of a saturated solution, adding more solute, and lowering temperature back without disturbing the solution  The solution is unstable, it will crystallize if disturbed, giving off energy, and producing heat

 When dissolved in water, it loses at least one hydrogen atom forming hydronium ions (H 3 O + )  Taste sour  Are corrosive  Can damage skin or tissue  React with an indicator (litmus paper) to produce a predictable color change (red)

Food contains acid – Citrus food = citric acid – Yogurt & buttermilk = lactic acid – Vinegar = acetic acid Stomach uses hydrochloric acid Four acids are vital to industry – Sulfuric acid = car batteries & manufacturing of fertilizers – Phosphoric acid = detergents, fertilizers, and soft drinks – Nitric acid = fertilizers – Hydrochloric acid = used to clean steel

 Forms hydroxide ions (OH - ) in a water solution  Or accepts Hydronium ions (H 3 O + ) from acids  Feel slippery in solution  React with indicators to produce predictable color changes  Many are crystalline solids in pure undissolved state  Strong bases are corrosive

 Used in cleaning products, medications, fabrics and deodorants

 Process in which an ionic solid separates into its positive and negative ions  Acid = (H 3 O + )  Base = (OH - ) and does not combine with water

 A chemical reaction between an acid and a base in water solution  H 3 O + + OH -  2 H 2 O

 Acid + Base  Salt + H 2 O  Salt = negative ion from acid and positive ion from base

 Base that does not contain OH -  Forms NH 4 + in H 2 O  NH 3 + H 2 O  NH OH -

 Depends on how completely an acid or base separates into ions when dissolved in water  Strong acid = ionizes almost completely  Weak acid = only partly ionizes in solution  Strong base = dissociates completely  Weak base = does not ionize completely

 Strong acids and bases conduct more electricity than weak ones  Equations for strong acids and bases use a single arrow  indicating ions are formed  Equations for weak acids and bases use double arrows pointing in opposite directions  indicating an incomplete reaction

 Term used to describe the amount of acid or base dissolved in solution  Different from strength  Strength = classification  Concentration = amount

 Measure of the concentration of H ions in a solution  how acidic or basic it is  Determined using a universal indicator paper (litmus) or a pH meter  pH lower than 7 = acid Strong acid = pH  pH greater than 7 = basic Strong base = pH  pH exactly 7 = neutral