1. Water and Solutions
Ch. 13

2. Properties of Water Colorless Odorless Neutral pH; 7 Polar molecule
Positive H+ region and Negative O2- region
Exists in all 3 phases of matter
Solid form is less dense than liquid
Why is this important?

3. Density of Water As water cools, the molecules move closer together
Volume decreases and density increases
At 4oC water the most dense it can be; almost 1.0g/ml
Below 4oC, H-bonds force the molecules in to hexagonal crystals
Expanding the ice lowers the density to g/ml

4. Special Properties of Water
High Surface Tension 表面张力
Attraction between molecules on the surface of water; cohesion
Causes water to bead up; form rain drops

5. Special Properties of Water
Capillary Action 毛细作用
Attraction between molecules in a liquid and the molecules on a surface; adhesion
Pulls water upwards against the force of gravity
Allows tall trees and plants to exist

6. Special Properties of Water
High Specific Heat Capacity比热容:
Amount of energy need to raise the temperature 1 g of substance 1oC
Water: J/goC
Why is this important to living things?
Water absorbs the heat produced by biological processes
1 g of sugar produces 16.7 J
Water absorbs heat from the sun; keeps the Earth cool during the day and warm as night.

7. Aqueous Solutions A mixture of water and dissolved minerals
Heterogeneous or Homogenous?
What are the two parts of a solution called?
Solute and Solvent
Solution Concentrations
Solutions with a high concentration of solute are called concentrated 浓缩的
Solutions with a low concentration of solute are called diluted稀释的

8. Solubility
The concentration of solute in a solvent depends on the solute’s solubility溶解度
Maximum amount of solute that can dissolve in a given solvent
Creates 3 levels of concentration:
Unsaturated不饱和的
-solute dissolves; more can be added
Saturated饱和的
-Past maximum solute level; extra solute can bee seen in solvent
Supersaturated过饱和的
- Applying heat dissolves extra solute but solution will crystallize when cooled

9. Solution Concentration
Why are the terms “Concentrated” and “Diluted” not useful in a Chemistry lab?
They are relative terms. The solution is “diluted” but compared to what?
When doing reactions you need to know the exact concentration of chemicals being used
Molarity物质的量浓度(M)
Number of moles/L of a substance in a solution
Ex. 1 M HCl = 1 mol of HCl/ 1 L of H2O

10. Calculating Molarity = 349 g KBr M = mol/L
M= mol NaCl/ 4.5 L H2O
M= 0.15 mol/L = 0.15 M
3 mol KBr
119.0 g KBr
1 L H2O
977.6 mL H2O
= 349 g KBr
1 mol KBr
1000 mL H2O
1 L H2O

11. Formation of Solutions
Solubility determine if solutions can form
Simple rule for solutions:
“Like dissolves Like”相似相溶
Substances with similar properties will dissolve into each other
Polar vs. Non-polar Substances
Polar substances will dissolve polar substances
Salts, Sugars, water, acids…
Non-polar dissolve non-polar
Oils, fats, hydrocarbons…
Non-polar + polar = heterogeneous mixture

12. Formation of Solutions
Factors that effect solubility:
Size of solutes
Temperature of solvent
Stirring or mixing action
Solutions cover all phases of matter:

13. Types of Solutions Electrolytes电解质 Non-electrolytes非电解质
Water dissolves ionic compounds into free floating ions
The charged particles allow the conduction of electricity through the water
More ions = stronger electrolyte
Does pure water conduct electricity?
Non-electrolytes非电解质
Molecules and organic compounds do not break into ions in water
Cannot conduct electricity

14. Mixtures with Larger Particles
Suspensions悬浮液
Heterogeneous mixtures with particles large and 1 micrometer
When stirred the mixture appears homogenous but over time the solid material will settle on the bottom
Ex. whole milk, dirty water, paint…
Colloids胶体
“Heterogeneous” mixture completely and evenly spread throughout another substance
Particles never settle or separate
Will glow due to Tyndall effect丁达尔效应
Light particles bounce of particles inside substance
Ex. Regular milk, whipped cream, jelly…

15. Effects of Solutes on Substances
Solutes change how particles in solvents interact
Boiling Point Elevation沸点升高:
Solutes take up space at the top of a liquid solvent
Less surface for liquid molecules to escape into gas molecules
Temperature must be raised higher than the normal boiling point
Freezing Point Depression凝固点降低:
Solutes prevent liquid solvent particles from getting close enough to change to a solid state
Temperature must be below the normal freezing point