1. Water and Aqueous Systems

2. Water Molecule

3. Hydrogen Bonds

4. Properties of Water Resulting from Hydrogen Bonding
High surface tension
Low vapor pressure
High specific heat capacity
High heat of vaporization
High boiling point

5. Surface Properties
Surface tension: the inward pull or force the tends to minimize the surface area of a liquid
Water molecules are only hydrogen bonded on one side and are not attracted to the air

6. Water Droplets
Surface tension holds liquids in a spherical shape- smallest surface area for a given volume
Gravity flattens it
The stronger the surface tension the more spherical the drop

7. Surfactant Surface Acting Agent Decreases surface tension
Interferes with hydrogen bonding

9. Specific Heat Capacity
Because of hydrogen bonding the specific heat of water is higher than that of most other substances

10. Evaporation and Condensation
Evaporation kJ per gram is absorbed
Condensation: 2.26 kJ per gram is released

11. Melting Points and Boiling Points of Some Substances with Low Molar Mass
Name of Substance
Formula
Molar Mass (g/mol)
Melting Point (oC)
Boiling Point (oC)
Methane
CH4 16
-183
-164
Ammonia
NH3 17
-77.7
-33.3
Water
H2O 18
100
Neon Ne 20
-249
-246
Methanol
CH3OH 32
-93.9
64.9
Hydrogen Sulfide
H2S 34
-85.5
-60.7

12. Boiling Points and Melting Points
Molecular compounds with low molar masses tend to have low boiling points
Boling Point: oC
Boiling Point: 100oC

13. Hydrogen Bonding in Ice

14. Ice Snowflake Symmetry is Due to Hydrogen Bonding
Ice is less dense than Water

15. Solvents and Solutes
Aqueous Solutions: Water samples containing dissolved substances
Solute: the dissolved particles
Solvent: The medium the particles dissolve in
Solutions are homogeneous mixtures
Solutes can be solids, liquids or gases- ionic or molecular

16. Like Dissolves Like
Solvation: the process that occurs when a solute dissolves
H2O and NaCl
H2O and Oil

17. Electrolytes and Nonelctrolytes
Electrolytes: compounds that conduct electricity in aqueous solution or molten state
ALL Ionic compounds are electrolytes
Not all conduct to the same degree
Nonelectrolytes: don’t conduct

19. Water of Hydration The water in a crystal CuSO4*5H20
A compound that contains water of hydration is called a hydrate

20. Water of Hydration
Effloresce: if a hydrate has a higher vapor pressure than the water in the air the hydrate will lose water

21. Water of Hydration Hygroscopic: remove water from the air
Desiccants: drying agents (remove water from the air)

22. Water of Hydration
Deliquescent: can remove enough water from the air to form a solution

23. Suspensions Mixtures from which particles settle out upon standing
Bigger particles than in a solution
Heterogeneous

24. Colloids
Heterogeneous mixtures containing particles in between a suspension and a solution

25. Tyndall Effect
Particles in a colloid scatter visible light in all directions
Suspensions also exhibit Tyndall effect but solutions NEVER do

26. Brownian Motion
Particles in a colloid viewed under a microscope will flash (scintillate) because of Brownian motion- the chaotic motion of the particles
Caused by the collisions between water molecules and colloidal particles

27. Emulsions Colloidal dispersions of liquids in liquids
An emulsifying agent is necessary for the formation and maintenance of an emulsion