1. WATER And Solution Formation
Ch. 15 & 16
WATER
And
Solution Formation

2. Water is unique Polar Molecular Compound
IMF = Hydrogen “bonds” = VERY STRONG
Causes :
High boiling point
Low vapor pressure
High surface tension
Surfactant: disrupts H-bond, lowers surface tension

3. Solid Water (ICE) Unique structure due to H-bond
Ice floats bc of structure
Less dense than liquid
Open hexagon structure
or honeycombed shape

4. Solutions Solvent: Dissolving medium (does the dissolving)
Solute: the dissolved particles (gets dissolved)
Solvation: the dissolving process
“like dissolves like”
Water is called the UNIVERSAL SOLVENT

5. Electrolytes Electrolyte: conducts electricity when dissolved in water
All ionic compounds are electrolytes
Dissociate into ions.

6. Nonelectrolytes Nonelectrolyte: doesn’t conduct electricity
Most molecular compounds
Especially carbon based (organic) compounds

7. Solutions Notes

8. Properties of Liquids Both Gases and liquids have kinetic energy
This means the molecules are constantly moving
Key difference:
Gases have no intermolecular forces
Liquids do!

9. Evaporation vs. Vaporization
Vaporization: phase change from liquid to gas when the liquid is boiling
Evaporation: phase change from liquid to gas when liquid is not boiling
Happens at the surface because the KE of the molecules is greater so they become gases.

10. Boiling Point
Temperature where a liquid begins to boil and vaporize. Happens when the vapor pressure of the liquid is equal to the external pressure.
When pressure decreases boiling point decreases
This is why water boils faster at higher altitudes- increase in altitude = decrease in pressure

11. Intermolecular Forces Review
Forces between molecules in a compound
Weaker than ionic and covalent bonds
Hydrogen bonding is strongest, Van der wals are weakest.

12. Properties of Water
Water molecules are polar (unequal distribution of charge!)
Oxygen atoms have slightly negative charge
Hydrogen atoms have slightly positive charge
Hydrogen bonding gives water unique properties of high surface tension and low vapor pressure.

14. Two types of mixtures
Homogeneous: mixtures with uniform properties throughout
Heterogeneous: mixtures that have two or more components or phases
Solution: A homogeneous mixture of two or more substances in a single phase.

15. What happens when sugar dissolves?
Sugar molecules get distributed uniformly among the water molecules.

16. What does it mean to be soluble?
Soluble- capable of being dissolved
Is sugar soluble in water?
What about oil?
Like dissolves like! (oil is nonpolar, water is polar)

17. Parts of a solution
Solute: the substance that is being dissolved (sugar, salt, hot chocolate mix)
Solvent: the substance that is having something dissolved into it (usually water). Also called the dissolving medium
Usually more solvent than solute in a solution

18. Types of solutions
Solutions can be in each of the three phases of matter: solid, liquid gas!
Ex: 14 karat and 18 karat gold are solutions.

19. Properties of solutes
Electrolytes: a substance that dissolves in water and conducts an electric current.
Ex: NaCl, or any soluble ionic compound
Nonelectrolyte: substance that dissolves in water that does not conduct electric current.
Ex: Sugar

20. Factors that increase the rate of dissolution
Dissolution: process of a substance dissolving
Increased surface area: dissolving happens at the surface. A sugar cube will dissolve slower than a spoonful of sugar.
Agitation: stirring or shaking a solution helps to dissolve the solids faster
Heating: as the solvent temp heats up the particles move faster (faster kinetic energy) so they can dissolve faster--for solids!

21. Solubility
Solution equilibrium: the physical state where dissolving and crystalization are happening at the same time
Saturated solution: a solution that contains the maximum amount of dissolved solute. (full, can’t take any more)
Unsaturated: a solution that contains less solute than a saturated solution (still has room for more)

22. Solubility
Solubility: the amount of a substance required to form a saturated solution with a specific amount of solvent at a specific temperature.
Ex: at 20°C exactly 35.9 g of NaCl will dissolve in 100 mL of water.

23. Solubility Graph and calculation
Solubility is determined in grams of solute
100 g of water
What is the solubility of sodium nitrate at 20oC?
How much ammonium chloride can be dissolved in 200g of water at 30oC?
How does gas solubility change with temp?

24. Solution calculations
Molarity (M): moles solute/L soln
Molality (m): moles solute/kg solvent
M&m problems can be solved by setting up ratios!
Percent concentration: mass solute/mass soln
~~~May need to convert between mass and moles~~~