Eriksons Developmental Stages Video

9/2/2008 – Class Notes

Chemistry – The Central Science

Pre-Scientific Method – Alchemists

Scientific Method – 1661, England Boyle

• Controlled Experiment
  
• Observation of Results
  
• Hypothesis
  
• Natural Law or Theory
  

  A Theory explains the behavior of a phenomenon
  

  A Natural Law doesn’t explain behavior, rather it states that there is a measurable relationship of some kind.
  

Measurements

There will never be 100% precise measurement.

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Measuring Volume: (Standard L or mL)

Graduated Cylinder

Beaker – fixed quantity, least accurate

Volumetric Flask – fixed quantity

Pipette – fixed quantity

Graduated Burette

Every measurement has a unit:

10 cal = energy/heat

10 sec = time – stop watch

10 kg = mass – balance, scale

10 cm = length – ruler

Every measurement has a degree of uncertainty ex. ±.001

Significant Digits

A significant digit is the digit that reflects the accuracy of the measurement.

Whole Numbers:

10,000 has 1 significant digit

10,005 has 5 significant digits

10,010 has 4 significant digits

Decimals – any zero preceding the decimal is non significant, any zero following the decimal after a non zero number is significant.

0.1 has 1 significant digit

0.100 has 3 significant digits

0.1000 has 4 significant digit

0.0002 has 1 significant digit

0.000200 has 3 significant digits

11.2420000 has 9 significant digits

Important

When solving a problem, both sides must have equal significant digits. Solve first, then round off to get the same number of significant digits in both the question and the answer.

Example:

Measure the Density mass/volume

1.2cm

v=1.2cm3

v=1.2*1.2*1.2

v=1.728cm

v=1.73 (rounded off so that the answer has the same amount of significant digits)

m=10.0052g

10.0052cm = 5.7833

1.73mL

The number with the least amount of significant digits is 1.73 and the answer will be converted into 3 significant digits

Density = 5.79

Scientific Notation

Represent very large or very small numbers in powers of 10

Any number raised to the power of zero is 1

For numbers 1 or higher, move the decimal to the left to determine the power

1=100

1=2000

10=101

100=102

1,000=103

10,000=104

1,000,000=106 or 1×106

1,200,000,000=1.2×109

For numbers less then 1, move the decimal to the right to determine the power

0.1 =10-1

0.01=10-2

0.001=10-3

0.0001=10-4

0.00001=10-5

25°c = Room Temp