October 25th, 2010: Isotopes & Atoms (Zac)

Atomic Number
- Atomic # - # of protons
- Atomic mass - atomic number = # of Neutrons
- Isotopes - same atom but different mass
- For example, there are 3 types of chlorine atoms (35H, 36H, and 37H)

Mass Spectrometers
- Are used to determine the abundance ad mass of the isotopes of the element
- A device known as a mass spectrometer can be used to determine the "relative abudance" and the "mass" of  the "isotopes" of the elements

Oct.21,2010:Quantum Mechanics (brian)

Bohr Theory
-electrons are particles that must be in the orbital of an atom
-Quantum Theory
-an electron is like a cloud of negative energy/wave
-orbitals are areas in a 3D space where the electrons most probably are
-energy of the electron is in its vibrational modes
-photons are produced when high energy modes change to lower energy modes

1. S orbitals
   - hold 2 electrons 
2. P orbitals
   -have 3 suborbitals
   -each contain 2 electrons
   -total electrons = 6  
3. D orbitals
   -have 5 suborbitals
   -each contain 2 electrons
   -total electrons = 10
4. F orbitals
   -have 7 suborbitals
   -each contrain 2 electrons
   -total electrons = 14

                                

                  

October 15th, 2010: Bohr's Model (Zac)

- Bohr (1920's) based his model on the energy (light) emitted by different atoms
- Each atom has a spectra of light

- To explain this emmission spectra, Bohr suggested that electrons occupy shells or orbitals
BOHR'S THEORY
- Electrons exist in orbitals
- When they absorb energy the move to a higher orbital
- As they fall from a higher orbital to a lower one they release energy as a photon of light

October 13, 2010: Atomic Theory (Angelo)

Atomic Theory:
- Many theories have been made to explain atoms. Not all of them are true today.

Aristotle (384 B.C. to 322 B.C.):
- Invented the four elements theory. (Water, Earth, Wind, and Fire)
- The four elements theory lasted for about 2000 years.
- It is not a scientific theory because it could not be tested against observation.

Democritus (460 B.C. to 370 B.C.):
- In 300 B.C., Democritus said atoms were indivisible particles.
- This was the first mention of atoms (atomus).
- Not a testable theory, only a conceptual model.
- No mention of any atomic nucleus or its consituents.
- Cannot be used to explain chemical reactions.

Lavoisier (1743 to 1794):
- Created Law of Conservation of Mass.
          - States that the mass of a system will remain constant.
- Created Law of Definite Proportions
          - Water is always 11% H (Hydrogen) and 89% O (Oxygen)

Proust (1754 to 1826):
- If a compound is broken down into its constituents, the products exist in the same ratio as in the compound.
- Proust experimentally proved Lavoisier's laws.

Dalton (1766 to 1844):
- Thought atoms are solid, indestructable spheres (like Billiard balls).
- Thought each element had different types of atoms (different color, shape, etc.).
- Based on the Law of Conservation of Mass.
- Have a molecule (atoms combine in simple whole number ratios) explains the Law of Constant Composition.
- If the atoms are not destroyed then the mass does not change.

J.J. Thompson (1856 to 1940):
- Raisin bun
- Solid, positive spheres, with negative particles embedded in them.
- First atomic theory to have positive (protons) and negative (electron) charges.
- Demonstrated the existence of all electrons using a cathode ray tube

Rutherford (1871 to 1937):
- Showed that atoms have a positive, dense centre with electrons outside it.
- Resulted in planetary model.
- Explains why electrons spin around nulceus.
- Suggest atoms are mostly empty space.

Sodium Chloride Lab (Brian)

Problem: What is the maximum amount of table salt that can be dissoloved in 200mL of water?

Observations:

   

Trial	Volume of Water (mL)	Mass of Salt (g)
1	10	1.01g
2	20	2.14g
3	40	4.02

Analysis:

    1. the units for the slope of our graph was g/mL

    2. the slope repersents how many g of salt in a certain amout of ml of water

    3. our best fit line prediction was 20.1 g

   


              

20.1 - 70.8 = -252
     20.1

September 30th, 2010 - Density & Graphing (Zac)

-The density of an object is its mass divided by its volume.
   eg. d= m/v
-It is usually expressed kg/L, kg/m3, or g/km3 (3 - to the power of 3)
-All Graphs must contain 5 important things
1. Labelled Axis
2. Appropriate Scale
3. Title
4. Data Points
5. Line of Best Fit
- There are 3 things you can do with a graph
1. Read it
2. Find the slope (rise/run)
3. Find the area under the graph

September 28, 2010: Dimensional Analysis (Angelo)

Dimensional Analysis:
- Want to know what 100 km/h (kilometres per hour) is in mi/h (miles per hour)?
- Just like converting between currencies, in chemistry, it is usually necessary to convert between units.
- This process is called Dimensional Analysis

Steps for the Dimensional Analysis process:

1. Find the unit equality
2. Find the conversion factor
3. Apply the conversion factor
4. Cancel Units

EXAMPLES:

1. How many miles are equal to 200 kilometres?

    Find the unit equality: 1 mile (mi.) = 1.6 kilometres (km.)
    Find the conversion factor: 1 = 1 mi. / 1.6 km.
    Apply the conversion factor: (200 km.) x (1 mi. / 1.6 km.)
    Cancel Units: 125 mi.

    Answer: 200 km. is equal to 125 mi.

2. What is 100 kilometres per hour in metres per second?

    Find the unit equality: 1000 metres (m.) = 1 kilometre (km.) and   
                                    3600 seconds (s.) = 1 hour (h.)
    Find the conversion factor: 1 = 1000 m. / 1 km. and 
                                           1 = 1 h. / 3600 s.
    Apply the conversion factor: (100 km/h) x (1000 m. / 1 km.) x (1 h. / 3600 s.)
    Cancel Units: 28 m./s.

    Answer: 100 km./h. is equal to 28 m./s.

Here's a helpful example of changing inches to feet using Dimensional Analysis: