CAS CH 171 Lecture 1: CH171 Unit 1 Notes
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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