Ch Solutions

Sec. 1 – How Solutions Form Solution = homogeneous mixture mixed at the molecular level; may be liquids, gases, or solids(alloy) Solute  Substance being dissolved Solvent  Substance doing the dissolving

How does dissolving happen? Water molecules are polar so their (-) ends attach to the (+) ends of particles pulling them into solution.

The moving water & solid molecules spread evenly to form a solution. *Note: When making an alloy soln, you must melt the solids.

Rate of Dissolving Speeding up dissolving rate: –Stir the solution –Increase surface area of solid by crushing it into smaller pieces –Increase the Temp. (speeds up movement) –Gas in a liquid: cool the liquid & increase the pressure of the gas

Sec. 2 – Dissolving without Water Nonpolar materials have no (+) or (-) areas, b/c they share electrons evenly.

Nonpolar Molecules: not attracted to polar molecules in water nonpolar solvents dissolve nonpolar solvents “like dissolves like” large particles of C & H - hydrocarbons

Useful Nonpolar Molecules: Oils – contain hydrocarbons Soaps – has polar and nonpolar properties Vitamin A – dissolves in the fats of body cells (Vit B & C are polar) Most solvents are toxic

Section 3 – Solubility & Concentration SolubilitySolubility – –The amount of substance that CAN dissolve in a solvent –Depends on the nature of the substance –Solubilities can be compared by measuring Concentration -Concentration - Concentrated solution –A large amount of solute in the solvent Dilute solution –A small amount of solute in the solvent Concentrations are expressed as percent by volume of solute

Types of solutions… Saturated – –Contains ALL the solute it can hold at a given temp. (perfect) As temp. of a liquid solvent increases, the amount of solid solute it can dissolve also increases A solubility curve is used to display how much solute can be dissolved at given temps.

Types of solutions… Unsaturated – –Can hold more solute at a given temp. –Not saturated (can still add to it)

Types of solutions… Supersaturated – –Contains more solute than a saturated one at the same temperature. –Over saturated (too far)

Supersaturation… Supersaturated solutions are made by raising the temp. of a saturated solution, adding more solute and decreasing the temp. back down without disturbing the solution Unstable – if disturbed, they will crystallize –This gives off energy & produces heat

Section 4 – Particles in Solution electrolyteelectrolyte – – Compounds that form ions (ionize) & conduct electricity in water NonelectrolyteNonelectrolyte – Substances that do not ionize and cannot conduct electricity

Formation of Ions “ Ionization ” –Molecules break apart in water, causing ions to become charged (ions) “ Dissociation ” –Ionic solid separates into positive & negative ions

Effects of solute particles All particles affect the physical properties of the solvent – Polar, nonpolar, electrolyte & nonelectrolyte Adding solute to solvent lowers freezing point & raises the boiling point