Solutions
Properties of Solutions Why do you use rock salt when making homemade ice cream? Why do they place sand or Calcium chloride on the overpasses when there is chance of freezing Why do you use 50% antifreeze and 50% water in your car?
Solution Formation Three ways to speed up dissolving process of solutes in solvents Agitate it (Stir it) Crush it (reduce the surface area) Heat it (increase the kinetic energy of the molecules)
Solubility 100 grams of water add 36.o grams of NaCl 25 C All the salt dissolves One more gram and it does not
Kinetic Molecular Theory Kinetic Molecular theory says that molecules are in constant motion and therefore they should continually bombard the solute until it is dissolved However there is an equilibrium point where there is too much solute in the solvent
Terminology Saturated Solution- maximum amount of solute for a given solvent at constant temperature Solubility- amount that dissolves in a given quantity of a solvent at a given temperature to produce a saturated solution Expressed in grams of solute per 100 grams of solvent
Terminology unsaturated- solution that contains less solutes than a saturated solution Supersaturated- more solute in the solvent then what is suppose to be there (rock candy) YouTube - Supersaturated Sodium Acetate
Terminology Miscible- two liquids that dissolve in each other Immiscible- liquids that are insoluble in each other
Mythbusters and Chemistry YouTube - Superheating of water (Mythbusters) YouTube - Superheating water to make it explode It is the impurities in water that enable it to boil at 100 degrees Celsius Remember it is the universal solvent
Factors affecting solubility Solubility versus temperature graphs No pressure! most substances as temperature increases their solubility increases BUT NOT ALL ACT LIKE THIS!
Favorite Soda Which scenario will the CO2 release faster It is cold outside and you leave your coke can open in your truck It is August in Texas and you leave your coke can open in your truck
Applications Candy- Rock Candy- supersaturated solutions Ice cream Cloud seeding YouTube - How humans make rain - The Science of Superstorms - BBC YouTube - Cloud seeding in the Texas panhandle.
Molarity Yesterday you made solutions of different concentrations Concentration refers to how much solute is there- the more there is the more solute that is dissolved in it! Dilute- refers to one that has a low concentration of solute
Molarity (M) Way to express the concentration quantitatively Moles of solute dissolved per liter of solution Also known as molar concentration moles of solute = liters of solution x molarity (mol/l)
Dilutions Dilution reduces the moles of solute per unit volume- total moles of solute in solution does not change
Percent Solutions Used for liquids miscible in other liquids Like alcohol- Isopropyl alcohol can be bought with 50%, 70%, or 90% concentration.
Colligative Properties Three important colligative properties include decrease vapor pressure boiling point elevation freezing point depression
Vapor Pressure is the pressure exerted by a vapor that is a dynamic equilibrium with its liquid in a closed system a solute that is nonvolatile (not easily vaporized) always has a lower vapor pressure in a solvent glucose, sodium chloride
Boiling Point Elevation In order to get those particles to the next phase change, you must increase the kinetic energy So when you add more particles it takes more energy in order to get the solution to boil That is why you use antifreeze in cars
Freezing Point Depression When substances freeze, they take on orderly patterns Solutes disrupt this orderly pattern Causes more Kinetic energy needed to be withdrawn from the system prior to freezing The difference between the original freezing point and the new one is called the freezing point depression