2. The Scientific Method
• Scientists are always faced with the task of properly
designing an experiment to test any and all variables.
– Example: You decide to test what happens to a balloon when
placed in a warm environment (like a moderately hot oven)
versus what happens to a balloon placed in a cold environment
(like the freezer).
• Several important key terms in designing an experiment:
– Constants - The variables that never change in the experiment.
• Ex: The size of the balloon, the type of balloon, etc.
– Control - The "normal" in an experiment. This is usually what you compare your experiment
to.
• Ex: A balloon placed at room temperature.
– Independent Variable – The variable that you directly control.
• Ex: Where you placed the balloon (oven or freezer).
– Dependent Variable – The variable that changes because of the independent variable.
• Ex: The size of the balloon
3. Covalent vs. Ionic Bonds
• Know the difference between covalent and
ionic bonds.
– Covalent bonds are always between a non-metal
and a non-metal. (groups 4-7)
• Ex: CCl4
• These are ALWAYS referred to as molecules.
– Ionic bonds are always between a metal with a
non-metal. (groups 1-3 with groups 4-7)
• Ex: LiF
• These are usually referred to as compounds.
4. Naming Ionic Bonds
• Name the cation first and the anion second.
• Change the ending of the anion to –ide.
– Ex: Name MgCl2
• Cation: Mg+2 magnesium
• Anion: Cl-1 chloride
– So the name is magnesium chloride
• Note: You don’t have to worry about the
subscripts. BUT MAKE SURE YOUR
CHARGES= “0”
• Do not forget your polyatomic ions.
5. Naming Covalent Molecules
– 1: mono- • Covalent molecules are named in a
– 2: di- similar fashion, except you must use
– 3: tri- the prefixes you learned in class.
– 4: tetra-
– 5: penta- • Name the element as is placing the
– 6: hexa- prefixes for the subscripts and change
– 7: hepta- the ending to –ide.
– 8: octa- – C4H10
– 9: nona- • Tetracarbon decahydride
– 10: deca- – NO2
• Nitrogen Dioxide
6. Mixtures
• Mixtures are • Filtration
combinations of
substances that retain • Distillation
their physical and
chemical properties.
• You can separate • Chromatography
mixtures by using
different techniques. • Crystallization
• See if you can
remember these
separation techniques:
7. The Mole
• The mole is the SI unit used to measure the
amount of a substance.
• You should be able to convert back and forth
between atoms, moles, and grams.
• You should be able to do this for elements and
for compounds.
• Remember this roadmap:
Atoms moles mass (g)
8. Energy Diagrams
• Energy diagrams show
phase changes for a
molecule.
• These phase changes
occur as a result of the
relationship between
temperature and energy.
• Look at the diagram at
the left and think of
water and its phase
changes.
9. Phase changes
• Phase changes occur
wherever there is a flat
region in the diagram.
• What happens to the
molecules as you increase
the temperature?
• Think of the three states
of matter and what
happens to the molecules
in these states.
10. Phases and Their Energies
• As you increase the
temperature, molecules
gain more energy and
break their attraction.
• Look at the picture to
the right to help you
visualize the concept.
11. Reaction Rates
• Chemists can increase the rate of reactions by
doing one of several things:
– Increase the temperature of the substance
– Agitate the mixture
– Increase the surface area of a substance
– Decrease the volume of the container
– Increase the pressure of the container
12. Reaction Rates
• Reaction rates are related to the amount of collisions.
• Temperature: As you increase the temperature,
molecules move faster and collide more often.
• Agitation: You are causing the molecules to collide as
you mix them.
• Increasing the surface area: Allows for more
collisions to occur due to more space for them to occur.
• Decreasing the volume of the container: There is less
room for the molecules to move apart so they’ll run into
each other more often.
• Increasing the pressure: Molecules are more likely to
collide.
13. Gas Laws
• In order to solve any gas problems, you must
remember the following equation:
– PV = nRT
• P = pressure
• V = volume
• n = number of moles
• R = a constant and must be given
• T = temperature
