Solutions How Solutions Form Definitions Solution - homogeneous mixture Solute – substance being dissolved Solvent – substance doing the dissolving, present in greater amount Definitions Solute - KMnO4 Solvent - H2O Types of Solutions Based on state of solvent. All solid-liquid-gas combos are possible. EX: dental amalgam (alloy of silver, mercury, etc.) • liquid solute, solid solvent • solid solution Bell Ringer What is a solution? What is a solute? What is a solvent? Types of Solutions Unsaturated – not holding all the solute it can, will dissolve more. Saturated- holding all the solute it can, won’t dissolve any more. Supersaturated- holding more than theoretically possible, very unstable • Seed Crystal Dissolving Solvation • occurs at the surface of the solute • solvent particles surround solute particles (+/- attraction) • solute particles are pulled into solution Dissolving NaCl dissolving in water Rate of Solution Solids dissolve faster... • more stirring • small particle size (increased surface area) • high temperature Rate of Solution Gases dissolve faster... • no shaking or stirring • high pressure • low temperature Solutions Solubility & Concentration Concentration Concentrated solution • large amount of solute Dilute solution • small amount of solute Concentration % by Volume • usually liquid in liquid • EX: 10% juice = 10mL juice + 90mL water % by Mass • usually solid in liquid • EX: 20% NaCl = 20g NaCl + 80g water Concentration UNSATURATED SATURATED SUPERSATURATED SOLUTION SOLUTION SOLUTION more solute no more solute becomes unstable, dissolves dissolves crystals form concentration Solubility Solubility - maximum grams of solute that will dissolve in 100 g of solvent at a given temperature • varies with temperature • based on a saturated solution Solubility Solubility Curve - shows the dependence of solubility on temperature Solubility Solids are more soluble at... • high temperatures. Gases are more soluble at... • low temperatures. • high pressures (Henry’s Law). Bell Ringer What is a saturated solution? What is a supersaturated solution? What is solubility? What factors can affect solubility? Solutions Particles in Solution POLAR MOLECULE A molecule that has electrically charged areas. Also called a polar substance or polar compound. + DURACELL _ NON-POLAR SUBSTANCES Non-polar substances do not have charged ends DURACELL Aqueous (Water) Solutions Water dissolves ionic compounds and polar covalent molecules very well. • Salt is ionic- makes salt water. The rule is: “like dissolves like” Polar dissolves polar. Nonpolar dissolves nonpolar. Oil is nonpolar. • Oil and water don’t mix. STRUCTURE OF WATER H H O 1 molecule of water is made up of 2 hydrogen atoms bonded with 1 oxygen atom Water is Very Polar + H H + O - Universal Solvent Why is water so good at dissolving things? Because water is a polar molecule and is shaped like a wedge, it is able to break up substances into smaller pieces (dissolve). • Water 1) breaks the + and - charged pieces apart, and 2) surrounds them. How Ionic solids dissolve in water These ions have been pulled away from the main crystal structure by water’s polarity. H H H H H These ions have http://www.youtube.com/watch?v= been surrounded VTmfQUNLlMY by water, and are now dissolved! Bell Ringer What is a polar molecule? Why is water called the universal solvent? Hint: 2 parts to this answer Electrolytes and Nonelectrolytes Electrolytes- compounds that conduct an electric current in aqueous solution, or in the molten state • all ionic compounds are electrolytes because they dissociate into ions (they are also called “salts”) NaCl Na1+ and Cl1- • Must have charged particles that can move. Electrolytes and Nonelectrolytes Do not conduct? = Nonelectrolytes. • Most are molecular materials, because they do not have ions Not all electrolytes conduct to the same degree • there are weak electrolytes, and strong electrolytes • depends on: the degree of ionization Electrolytes- conduct electricity - + - + - + salt acetic acid sugar Weak Non- Electrolyte Electrolyte Electrolyte solute exists as solute exists as solute exists as ions only ions and molecules molecules only Colligative Properties Colligative properties - properties of solutions that depend only on solute concentration Freezing Point Depression • solutes lower the f.p. of a solvent Boiling Point Elevation • solutes raise the b.p. of a solvent Colligative Properties Freezing Point Depression Colligative Properties Boiling Point Elevation Solute particles “get in the way.” Colligative Properties Effect increases as the solute concentration increases. Uses: • antifreeze • making ice cream • salting icy roads • http://www.youtube.com/watch?v=PVL24HAesnc&list=PL 8dPuuaLjXtPHzzYuWy6fYEaX9mQQ8oGr&index=23 .