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:

September 23, 2010: Scientific Notation & S.D. (Brian)

Significant Digits

-Accuracy and precision is very important as well as communicating the accuracy carefully

-Calculators are not smart enough to decide what is and isn't precise

-Non zero digits are always significant

-If the zero is a place keeper its not significant


-Any numbers to the left of the decimal are significant
Example 6.004

-Zeros after another number are significant
Example 4.00

-When adding or subtracting round to the lest precise number
Example 8.1240 - 3.33 = 4.79 

-When multiplying or dividing round to the number with the fewest S.D.s
Example 4.83 x 9.1 = 43.953 = 44

-Constants on your data sheet have infinite S.D.'s

Scientific Notation
-Used to show really big numbers and really small number 

September 21st, 2010: Experimental Accuracy (Zac)

- In general, the maximum accuracy of any measurement is 1/2 of the smallest division of the measuring device
- A ruler with measurements of millimieters has a maximum accuracy of  plus or minus .5 mm.
Expressing Error
- Error is a fundamental part of science
- There are usually 3 reasons for error
1. Physical errors in the measuring device
2. 'Sloppy' measuring
3. Changing ambient conditions
Calculated Errors
- There are two different errors, absolute & percentage error 
Absolute Error
- Measured value minus accepted value 
Absolute Error = Measured - Accepted
Percent Error
- Most Common
- Eg.