Review with your table partner:
What are the two main types of bonds in molecules
and how do they compare?
Which elements do not form molecules? Why?
What are valence electrons?
Chemistry Review
Chemical Bonds
Elements form bonds in order to gain, lose or share
electrons so that they have ________________
__________________________.
1st energy level holds up to ____ electrons
2nd energy level holds up to ___ electrons
3rd energy level is stable with ___ in 1st 2
sublevels (holds 18 total electrons)
Magnesium: Atomic number 12
2 Types of Chemical Bonds
Ionic Bond:
___________ of electrons
Forms charged _________
Atom that gains an electron becomes a
____________
Atom that loses electron becomes a
__________________________.
Ions held together by attraction of opposite charges.
Covalent Bond:
Atoms _____electrons
Covalent bonds may be either polar or nonpolar.
Nonpolar covalent bond:
Electrons are shared _________ between the atoms.
Example: methane (CH4)
Polar covalent bond:
_____________ sharing of electrons because one
element has a stronger electronegativity.
The unequal sharing causing the molecule to have
__________ ________. (Negative on the side with
the stronger attraction to the electrons.)
Examples:
Water (H2O)
Ammonia (NH3)
Water is a polar molecule.
Oxygen has a greater attraction to the
shared electron than the hydrogen does.
Oxygen pole is negatively charged
Hydrogen pole is positively charged
Hydrogen bonds: the attraction between opposite
poles of two polar molecules.
Example: hydrogen bonds form between + hydrogen
pole of 1 water molecule and – oxygen pole of
another water molecule.
Note: hydrogen bonds are
attractions between
molecules (or distant parts
of a large molecule)
They are not the bonds
that hold together a
molecule.
Hydrogen Bond Animation
http://www.northland.cc.mn.us/biology/Biology1111/animatio
ns/hydrogenbonds.html
Discuss with your table partner:
How are polar covalent bonds similar to ionic
bonds and different from nonpolar covalent
bonds?
___________________________________________
___________________________________________
___________________________________________
___________________________________________
Molecular Bonds
_____
Covalent
______
Hydro_________:
“Water________” _____to charged poles of H2O
___________________
_______
Hydro_______:
“Water______”
_____________
Discuss with your table partner:
What do the words cohesive and adhesive mean?
Can you give some examples that show that water is
cohesive and can be adhesive?
How do these properties relate to the type of
chemical bond in a water molecule?
Water Video
http://www.youtube.com/watch?v=ihm0Xpw1jZo
Special Properties of H2O
Water is cohesive (attraction between _____particles)
Water molecules are held together by___________
____________.
 _____________
Water is adhesive (attraction between _________
particles). Due to its charged poles, water is
attracted to ________________________.
 _____________
http://news.cnet.com/8301-17938_105-57580453-1/wringing-out-a-space-station-washcloth-makes-water-clingy/
Or https://www.youtube.com/watch?v=fPA8Nl1XG4A
Video: Wringing a Washcloth in Space
Special Properties of H2O
Water _________ temperature change.
Water has a high specific heat which means it takes
____________ to heat compared to other
substances, and it also cools down more_________.
This property is due to the fact that it takes _____
energy to break the hydrogen bonds.
Coastal areas often have _______climates due to this
property.
Water Balloon Video
https://www.youtube.com/watch?v=qeDZQ9-gsjY
Heating Water vs. Oil Video
https://www.youtube.com/watch?v=fbuoYojx_Yg
Special Properties of H2O
• Water is a good solvent. (A solvent is a
substance that is ________________________.
Many ______ (such as salt) and _______ (such as
sugar) substances dissolve in water.
https://www.youtube.com/watch?v=0eNSnj4ZfZ8&list=PLY0vtkWGFeZ4
uJmvR_n3thMUWfaywuqxd
Video: Water and Living Things
pH Scale
The pH scale ranges from 0 to 14.
A pH of 7 is neutral
H+ = OHA pH below 7 is ______ greater H + (H+ > OH-)
A pH above 7 is ______ greater OH- (H+ < OH- )
Each step in
pH scale is a
10 fold change
(logarithmic
scale)
How does a pH of 5 compare to a pH of 7?
A.It is 2 x more acidic
B.It is 20 x more acidic
C.It is 100 x more acidic
D.It is 2 x less acidic
E.It is 20 x less acidic
F.It is 100 x less acidic
Answer = ________________
__________
Chemical Reactions
CH4 + 2O2
_________
CO2 + 2 H2O
___________
Subscript :
The number below the symbol for an element in the formula
of a molecule. It represents the number of atoms of that
element __________________________.
Subscripts
CH4 + 2O2
CO2 + 2 H2O
Coefficients
Coefficient:
The number in front of a formula for a molecule, in a chemical
equation. It indicates the __________________ that are
involved in the chemical reaction.
Balancing Chemical Equations
Equations must be balanced:
The number/type of atoms on the reactants side
must be equal to that on the products side.
________________________________________.
C6H12O6 + __O2
___CO2 + __ H2O
( ___ carbons, _____ hydrogen, ____oxygen on each side)
Metabolism:
____________________that happen in an
organism. These reactions build up or break down
molecules that are important for the functioning of
the organism.
Special Properties of Water
Water is a polar molecule:
Unequal sharing of electrons.
Oxygen pole has partial
negative charge and hydrogen
pole has partial positive
charge.
Polarity of water
molecules cause them
to form hydrogen
bonds
Hydrogen bonds:
Weak attractions between
two polar molecules
Water is a good solvent:
Ionic and polar molecules are
attracted to charged poles.
Water is cohesive (sticks
together) due to hydrogen bonds.
Water resists temperature change
(high specific heat= more energy
required to raise its temperature.)
Due to extra energy required to
break hydrogen bonds.