Chapter15-16 Water and SolutionsWhy I love water

___________________ ________________________________________Allows for life on earthIs impressive as both a liquid and a solid

How does it do all this?!?HYDROGEN BONDS!!!

Recall from previous chapters that _________________________ _________________________________________________________________________________________________________________________________________________________

Liquid: Surface Tensionwater sticks togetherDue to ____________. The molecules on the outside of drop are all attracted to the center molecules causing water to bead up.The ______________ ________________________________________________ Surface tension Makes it hard to spill!

Altering Surface TensionYou can ___________ ________________________________________________Play-Doh uses a surfactant molecule to bind fat to liquid, to make that strange texture of fun!

Liquid: Low Vapor Pressure (high boiling point)It takes a lot of energy to get water molecules to leave solution_____________________More energy = more heat needed = higher boiling point__________ less vapor at equilibrium (at a given temp) __________________

Becoming SolidWhen water freezes the hydrogen bonds move each molecule an exact distance apart decreasing densityTherefore _________________________________

Ice Floats!!!!Lets think about the significance of thisHomogeneous Aqueous SolutionsHomogeneous: _________ __________________________________________Aqueous: ____________ __________ water is the universal solventSolution: a ____________ _________ formed when one substance (_______) is dissolved into another (___________).

SolutionsContainSolute: _______________________ ______. Usually a solid (and sometimes a gas) and is the smaller part of the solution.Solvent_______________________ that accepts the solute. The most common solvent is H2O, therefore most solutions are aqueous.The __________________________all of the solution can pass through a filter paper. e.g. Kool Aid.Dissolving is a ______________ because no new substances are formed. Click here to see an animation of salt dissolving in water.

10Electrolytes conduct electricityWhen ionic solids dissolve in water, the positive and negative ions separate from each other and are free to move around.e.g. NaCl(s) Na+(aq) + Cl-(aq)The ions can piggy back electrons through the solution, allowing electricity to flowThese __________________________.e.g. Gatorade, Smart WaterStrong Electrolytes: ______________________Weak Electrolytes: ____________________

Rates of Dissolution:how fast a solute dissolves.There are 3 ways to speed up the dissolving process.1.) ____________________(Liquid)Higher Temp means higher KE of the solvent molecules which makes them move faster, and so, they get the job done quicker.2______________________________(solid)Instead of using one big lump, grind it up into small granules. Dissolving only occurs at the surface of the solute and this will increase the surface area.3.) _____________________________.This gets the dissolved particles, which are hanging around the surface, out of the way so that the water molecules can continue to dissolve (attack) the solid.How much solute can dissolve?Solubility: __________________________________________ _______________________________________________________________________________Units are in g/100 mL H2O or g/100g H2OE.g.For Sugar C12H22O11@ 20oC204g will dissolve in 100g of H2O@ 40oC238g @ 60oC287g

Scenario: 287g of sugar has been dissolved into 100mL of water at 60C. The water then cools down to 40C. What will happen?

Some more terms that describe solutions:

Saturated Solution: ________________ ________________________that can be dissolved. (equilibrium between dissolving and precipitation)Concentrated: the amount of solute (solid) dissolved is _____________________ pt.Dilute: the solution can still dissolve much more solute. (solid)Miscible: when _______________ _____ ____________________. (e.g. food coloring into water)Immiscible: _____________________ _ ___________________(e.g. oil & water)

Ways to affect saturationChange the pressure: ______ ________________(not really of solids). _____________________ ____________________________ ____________________________Why soda goes flat faster when it is NOT in a closed systemRelationship described by Henrys LawUse fizz keeper to save money!Change the Temperature________________________________For a ______________they have energy so they are stronger________________________________________If you lower temperature slowly you can trick the solvent into holding more than it is capable of (super saturated solution)For a ______________ more heat = more energy= more likely to leave as gas (makes them _______________________)

MolarityThe concentration of a solution is a measure of how much solute is dissolved in the solvent.Solutions can be __________________________.We need a more exact way to represent this concentration.The most common way to represent concentration is by _______ ___________Molarity (M) = # moles of solute in 1L of solution (not solvent)i.e Molarity (M) = __________________An exampleWhat is the Molarity of a solution if 60.g of LiCl is dissolved into water up to a level of 2.0LFirst: find # moles of LiClNeed to find Molar Mass:

M = n = V = 0.708 M (pron. Molar)Example #2How many grams of Ba(NO3)2 is required to make 250 mL of 0.5 M solution? (A typical lab prep skill!)Find # moles needed first:Convert mL to L Solve for MolesNext, convert moles to mass using Molar Mass (M)

A class example to do.You have 12.52 g of Calcium Carbonate and are asked to make a 0.25M solution. What Volume of water is require to do this?

Changing Concentrations of a solutionA solutions concentration can be changed either by adjusting the Volume or the solute._____________________________________________i.e. Molarity decreases (think of Crystal Light more water = more dilute)__________________________________________________________________________ i.e. Molarity increases. More difficult to do. Best to add more solute. We have a formula to help.

Mostly used for diluting concentrated acids.(Notice that Molar Mass is not relevant for this)Lets do a very important exampleIts Wed morning and Mrs. Walle is rushing to get her Chem lab prepared on time. She needs to prepare 500mL of 1.0 M HCl acid. But, she only has 12 M HCl acid on hand. What Volume of the concentrated acid does she use to prepare the new solution?Mi = 12 MMf = 1.0 MVi = ?Vf = 500mLMiVi = MfVfVi = 41.7 mLVi = 0.0417 L (mL is OK to use)Your turn to do an exampleIts lab day, and a mischievous Chem student has not read the lab directions. He (because girls always read instructions!) accidentally pours 50 mL of 2.0 M HCl acid into a beaker containing 200 mL of water. What is the new concentration of this acid?(Note: Use the correct final Volume)

Ans.Mf = 0.4 M

Colligative PropertiesWhen you make a solution it changes the properties of the solvent_______________________________________________________________(amount of solute dissolved)Vapor Pressure LoweringFreezing Point DepressionBoiling Point Elevation

Vapor Pressure LoweringIf the solute is less volatile than the solvent, the solute on the surface will not vaporize_______________________________________________________________________________________________Since pressure from the gas creates the vapor pressure, the vapor pressure decrease with increasing concentration

Freezing Point DepressionThe presence of a solute in a solvent disrupts the solvents ability to get organizedA solvent needs to get organized to freeze_______________________________________________________________________________________________________________________________Salting the roads on the where it snows.

Boiling Point ElevationThe solute particles monopolize space on the surface of the solution____________________________________________________________________________________________________________________________________More heat means a higher boiling point.