CAS CH 171 Lecture 1: CH171 Unit 1 Notes

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9/7-9/30: Unit 1
Scientific Method
1. Observations
Collecting data
2. Hypothesis
Questions
3. Experiments
Data
4. Develop Theory
Possible answer to question
5. More Experiments
Data
Terms
Chemistry - the study of matter
Matter - has mass, occupies space
Pure Substance
Constant composition
Fixed set of physical/chemical properties
Components cannot be physically separated
Molecule - smallest unit of a pure substance that retains its properties
Composed of particles called atoms
Atoms
Monatomic - 1 atom
Diatomic - 2 atoms
Triatomic - 3 atoms
Polyatomic - many atoms (>1)
Homoatomic - all of the same atoms
Heteroatomic - a mix of different atoms
Mass v. Weight - there is a difference
Mass - a measurement of the amount of matter present
Weight - mass x gravitational force
Physical Properties - observed changes with no chance in composition
Chemical Properties - requires a chemical change (observed changes with a change in composition)
Elements v. Compounds
Elements - pure substance (monatomic, homoatomic)
ex: oxygen
Compounds - pure substances (heteroatomic, polyatomic)
Mixtures
Can vary in composition and properties
Components can be physically separated WITHOUT changing the composition
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ex: iron and sand (iron can be separated using a magnet)
Metric System
base unit (length = meter)
common prefixes -
Mega (M) - 1000000 x basic unit
Kilo (k) - 1000 x basic unit
Deci (d) - 1/10 x basic unit
Centi (c) - 1/100 x basic unit
Milli (m) - 1/1000 x basic unit
Micro (u) - 1/1000000 x basic unit
Nano (n) - 1/1000000000 x basic unit
Pico (p) - 1/1000000000000 x basic unit
ex: An average parking spot is 3.0 meters wide. How many decimeters wide is the spot?
answer: 30 decimeters
ex: Your camera has 14.2 megapixels (Mpx). How many pixels (px) does it have?
answer: 14200000
common units -
Length - meter (m)
Volume - cubic meter (m^3)
Mass - gram (g)
Temperature - kelvin (K)
0 Kelvin = absolute zero
convert from Celsius to
Fahrenheit:
ex: 98.6 degrees Fahrenheit is considered normal body temperature. Convert that value to degrees
Celsius and Kelvin
answer: 37 degrees Celsius and 310 Kelvin
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ex: During the winter holiday, you go on a trip. At the airport the temperature is 28 degrees. However,
you don’t know if this is Fahrenheit or Celsius. Determine the correct scale and based on that answer,
convert the temperature into the other scale.
answer: it is 28 degrees Celsius, meaning that it is 82.4 degrees Fahrenheit
Time - second (s)
ex: 1L = 1dm^3
(1dm)(1dm)(1dm) = (10 cm)(10 cm)(10 cm) = 1000 cm
Scientific Notation
M x 10^n (n = integer)
1 < M < 10
ex: 14,200,000
answer: 1.42 x 10^7
ex: The diameter of a hydrogen atom is one-hundred millionth of a cm. Convert this to scientific
notation. Answer in the following format: # x 10^#cm
answer: 1 x 10^8 cm
Accuracy v. Precision
Accuracy - closest to correct answer
Precision - consistent set of answers
Significant Figures
Tell us the degree of accuracy
Zero Rules
Leading Zeros - zeros to the left of the first whole number - NOT SIGNIFICANT
Trailing Zeros -
zeros to the right of decimal - SIGNIFICANT
zeros to the left of decimal - NOT SIGNIFICANT UNLESS INDICATED
ways to indicate: scientific notation, decimal, line on top of last number
Buried Zeros - zeroes in between numbers - SIGNIFICANT
Multiplication/Dividing - answer must contain the same number of significant figures as the quantity
with the fewest used to calculate it
Addition/Subtraction - answer must contain the same number of significant figures to the right of the
decimal as the quantity with the fewest used to calculate it
ex: Calculate the area of a rectangular table that is 0.9m long and 2.2m wide
answer: 0.9 x 2.2 = 1.98 BUT 0.9 only has one significant figure so final answer is 2m (round 1.9
based on the 8 to the right of the 9)
ex: Subtract 3.025 from 460.5
answer: 460.5 - 3.025 = 457.475 BUT 460.5 only has one significant figure to the right of the decimal
so final answer is 457.5 (round 457.4 based on the 7 to the right of the 4)
ex: Convert the speed of light (3.0 x 10^8 m/s) to mi/hr, where 1 mi = 1.609 km.
work: 3.0 x 10^8 mile/1second = 1km/1000m = 1mi/1.609km = 60s/1min = 60min/1hr
(cancel out seconds, minutes and kilometers)
answer: 6.7 x 10^8 mi/hr
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