1. Aqueous Solutions

2. Thinking of the Molecules… Why do chemists work mainly with LIQUID solutions?!

4. Exothermic Rxns The temperature of the solution rises as solute is dissolved This is because the reaction causes a loss of heat in the system

5. Endothermic Rxn The temperature of the solution decreases as the solute is dissolved This is because the system is absorbing heat from its surroundings

6. Solution Process Model Simultaneous steps in solution creation 1.Solvent particles separate 2.Solute particles separate 3.Solute particles bond to solvent particles

7. Bond Breaking Requires energy Why?! ENDOTHERMIC REACTION

8. Bond Making Releases energy Why? EXOTHERMIC REACTION

9. RECAP: Label Exo and Endo Steps Simultaneous steps in solution creation 1.Solvent particles separate 2.Solute particles separate 3.Solute particles bond to solvent particles

10. Since dissolving is always 3 steps, whether the reaction is endo or exo depends on the SUM of the energies involved

11. If the reaction is ENDO More energy is needed to Break bonds than is given off in formation

12. If the reaction is EXO More energy is given off in formation of bonds than is needed to break bonds

13. Electrolytes Conduct electricity In order to conduct electricity, charged particles (ions) must be present in solution

14. Nonelectrolytes Do not conduct electricity Solutes form neutral molecules in solution, so no current is able to flow

15. Dissociation The separation of ions from the crystals of ionic compounds

16. i.e. NaCl dissolves in water forming Na+ and Cl- water surrounds the ions (solvation aka hydration) negative polar side of water attracts to the Na+, the positive side to the Cl-

17. this is represented through the symbol (aq) meaning aqueous solution i.e. K2SO4(s)  2K+(aq) + SO4 2 -(aq) note the charges always have to be balanced and equal

18. Ionization The formation of ions from polar molecules by the action of a solvent

19. i.e. HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq) Remember HCl is not an ionic substance, but it is molecular HCl breaks down into H+ and Cl-, but H+ is immediately hydrated into H3O+

20. i.e. HBr + H2O  H3O+(aq) + Br-(aq)