Dive in!

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Dive in!

• Chemistry Review and Properties of Water!

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The Atom

• The atom has three parts
• Protons
• Neutrons
• Electrons

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Lewis Dot Diagrams
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Chemical Bonds

• Compounds are stable combinations of different
  elements held together by chemical bonds. Two of
  the most common are ionic and covalent.
• When atom loses electron(s) and become positive,
  called cations, when they gain electron(s) and
  become negatively charged, called anions.
• Covalent bond formed when two atoms share one
  or more pairs of valence electrons. H-H, OO, N N

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Differences between Ionic Covalent bonds
Ionic Bonds Covalent Bonds
Bond between metals and non-metals Bond between non-metals
Metal loses its valence electrons to the non-metal (stolen!) Atoms share their valence electrons
The atoms are held together by the attraction between () (-) The atoms are bonded by the shared electrons
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Water!

• Our bodies are 70 water
• Vital for Transport carries substances in and
  out of cells
• Maintains body temperature
• Acts as a solvent

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Covalent bonding
Polar covalent bond unequal sharing of
electrons Why is water considered a polar
molecule? What is a partial positive and
partial negative charge? Hydrogen Bonds
Intermolecular bonds!!
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Covalent bonding vs. Hydrogen bonding
Hydrogen Bond
Covalent Bond
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Intermolecular Bonds p 17

• There are three types of intermolecular bonds
  (collectively referred to as van der Waals
  forces)
• London Forces exist between all atoms, very
  weak, unequal distribution of electrons
• Dipole-Dipole forces hold molecules together
  (--)
• Hydrogen Bonds H of one molecule and N, O, F of
  a nearby polar molecule

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Universal Solvent
Water is the solvent of Life! Solute substance
dissolved in a solvent to form a solution
Solvent fluid that dissolves solutes Example
Ice Tea water is the solvent and tea and sugar
the solutes
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Water-soluble protein
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Properties of Water
Cohesion, Adhesion and Surface Tension
cohesion water attracted to other water

molecules because of polar properties
adhesion water attracted to other materials
surface tension water is pulled together
creating the
smallest surface area possible
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Properties of Water
Capillary Action
Because water has both adhesive and cohesive
properties, capillary action is present.
Capillary Action waters adhesive property is
the cause of capillary action. Water is
attracted to some other material and then through
cohesion, other water molecules move too as a
result of the original adhesion. Ex
Think water in a straw Ex Water
moves through trees this way
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Surface tension
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Properties of Water
In order to raise the temperature of water, the
average molecular speed has to increase. It
takes much more energy to raise the temperature
of water compared to other solvents because
hydrogen bonds hold the water molecules
together! Water has a high heat capacity. The
specific heat is the amount of heat per unit mass
required to raise the temperature by one degree
Celsius.
High Heat Capacity
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Properties of Water
Density
Water is less dense as a solid! This is because
the hydrogen bonds are stable in ice each
molecule of water is bound to four of its
neighbors.
Solid water molecules are bonded together
space between fixed Liquid water molecules are
constantly bonding and rebonding space is
always changing
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Ice, water, vapor
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Properties of Water
So, can you name all of the properties of water?
Adhesion Cohesion Capillary action High
surface tension Holds heat to regulate
temperature (High heat capacity) Less dense as a
solid than a liquid
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Acids and Bases
Strength compared using pH scale Ranges from 0
14 Logarithmic Scale (gets 10x
bigger/smaller) Acid donates H when added to
aqueous solutions Ranges from pH 0-6.9 Base
breaks up into hydroxide (OH-) ions and
another compound when placed in an
aqueous solution Ranges from pH
7.1 14 Distilled water is pH 7.0 or neutral.
Why? H2O H OH-
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Acids and Bases
Buffers compounds used to maintain a contant pH
within a system
H2CO3 H HCO3- Carbonic acid
bicarbonate ion
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• Buffers resist changes to the pH of a solution
  when H or OH- is added to the solution.
• Buffers accept hydrogen ions from the solution
  when they are in excess and donate hydrogen ions
  when they have been depleted.

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Acids and Bases
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Making Biological Molecules
and H2O
Condensation Reaction
H2O
Hydrolysis Reaction