24.1 – How Solutions Form

Same composition, color, density and taste throughoutHomogenous

mixture

Exist in all states of matterThe air we breatheSterling silverBrassAlloys

Solute = Substance being dissolved

Solvent = Substance doing the dissolvingYou add a solute to a solventSolvents and Solutions exist in the same state of matter

Aqueous solution = solution with water as the solvent

Dissolving occurs at the surfaceParticles are always moving

Water molecules are polarThey 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 dissolving1. Stir the solution2. Increase temperature3. Increase pressure4. Reduce the crystal size

Surface area – breaking a solid into pieces or a powder increases surface areaDissolving takes place at the surfaceSo more surface area allows for

more solvent to come in contact with solute

The amount of a substance that can dissolve in a solventDepends on the nature of substances

The solubility of two substances can be compared by measuring

Expressed as a percent by volume of a solventA concentrated solution has a large amount of solute in the solvent

A dilute solution has a small amount of solute in the solvent

Saturated solutionContains 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 solutionAble to dissolve more solute at a given temperature

Solubility curveLine on a graph used to figure how much solute can dissolve at any temperature on the graph

Supersaturated solutionContains 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 (H3O+)

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 solutionOr accepts Hydronium ions (H3O+) 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 ionsAcid = (H3O+) Base = (OH-) and does not combine with water

A chemical reaction between an acid and a base in water solutionH3O+ + OH- 2 H2O

Acid + Base Salt + H2OSalt = negative ion from acid and positive ion from base

Base that does not contain OH-

Forms NH4+ in H2O

NH3 + H2O NH4+ + OH-

Depends on how completely an acid or base separates into ions when dissolved in waterStrong acid = ionizes almost

completelyWeak acid = only partly ionizes in

solutionStrong base = dissociates completelyWeak base = does not ionize

completely

Strong acids and bases conduct more electricity than weak ones

Equations for strong acids and bases use a single arrowindicating ions are formed

Equations for weak acids and bases use double arrows pointing in opposite directionsindicating an incomplete reaction

Term used to describe the amount of acid or base dissolved in solution

Different from strengthStrength = classificationConcentration = amount

Measure of the concentration of H ions in a solutionhow acidic or basic it is

Determined using a universal indicator paper (litmus) or a pH meterpH lower than 7 = acid

Strong acid = pH 0-3.0pH greater than 7 = basic

Strong base = pH 10-14pH exactly 7 = neutral