Honors Chemistry Chapter 15 Notes: Water and Aqueous Systems
(student edition)
Chapter 15 problems:26, 44, 59, 61, 67-71, 76, 79 (Hey! It’s time to review for the final - look at the 14 cumulative review ?’s on page 468 and pick at least a few to do - don’t pick the ones you know best - pick the ones you don’t remember – do these with your chapter problems, but on a separate piece of paper).
15.1 Water and its Properties
Water in the LiquidState:
Water has a shape. The oxygen atom forms a bond with the hydrogen atoms. Oxygen’s electronegativity causes the electrons to exist around it more. This gives the oxygen a partial charge and the hydrogen atoms a partial charge. Because of the electronegativity difference between the atoms and the bent shape of the molecule, water is considered a molecule. If two water molecules are close together, a dipole-dipole intermolecular force develops. This is IMF is called a bond. It occurs between the two water molecules and causes many different properties.
Surface Tension:The hydrogen bonds between water molecules causes water to have a surface tension. Surface tension is the inward , or pull, that tends to minimize surface area. A interferes with the hydrogen bonding and lowers the surface tension ( ).
Vapor Pressure:The hydrogen bonds between the water molecules causes water to have a vapor pressure. Vapor pressure is the result of water molecules leaving the . The
bonds prevent this from occurring.
Water in the SolidState
solids - dense - least volume liquids - dense - particles are
these previous 2 statements are true for most substances - that’s why solids sink in liquids
water is very unusual
Density Vs TempDensity Vs Temp
(most substances)(water)
when water molecules line up, they take up space than they would as a solid due to
and the honeycomb shape of the regular repeating pattern - that’s why ice floats
15.2Homogeneous Aqueous Systems
Two parts to a solution: : the part that gets dissolved.
: the part that does the dissolving.
The Solution Process:
Dissolving an ionic compound in water ( ):
Na+ Cl- Na+ Na+
Cl- Na+O-2O-2
Na+ Na+
+H+H+ H+H+O-2
Cl- Na+ O-2Cl-Cl-
Na+ Cl-H+H+
H+H+ Cl-Cl-
Step #1Step #2Step #3
Breakup theBreakup theFormation of the
( )( )( )
Electrolytes and Nonelectrolytes:
Some water solutions conduct electricity. These solutions are called .
Strong electrolytes: production of a lot of ions during the solution process.
NaCl(s) + H2O(l)
HCl(g) + H2O(l)
Weak electrolyte: production of a small amount of ions during the solution process.
HC2H3O2(l) + H2O(l) ↔
Hydrates:
Water of Hydration in Crystals: when an aqueous solution is , will be left behind.
Three possible situations can result:
a) pure crystals
b) crystals with some H2O
c) crystals w/ H2O combined chemically in a definite ratio - a
the water in a hydrate is called the water of hydration. These crystals are dry to the touch:
CuSO4 . 5 H2O yields
some definitions:
Anhydrous: crystals without .
Decrepitation: when water leaves a crystal .
Efflorescence: loss of water from a hydrate.
Hygroscopic Substances: absorb water from the .
Deliquescent: absorbs so much water, the crystals themselves in that water.
Calcium and Magnesium chloride - used in dirt roads and clay tennis courtskeep down dust
15.3Heterogeneous Aqueous Systems
Heterogeneous aqueous systems are called .
Types of Mechanical Mixtures: , , and
( ).
Mechanical mixtures exhibit the effect. This is the reflection of off of particles big enough to reflect light. An example is dust in the projection light at movie theaters.
A comparison of solutions and mechanical mixtures:
Category / Solutions / Colloids / Suspensions / EmulsionsHetero or
Homo
Particle
Size
Settling
Tyndall
Effect
Examples
The classification of matter chart:
1