Post on 05-Jan-2016
A.P. Ch. 1 Review Work
Chemical Foundations
Ch. 1: Scientific Method
Theories vs. Laws• Theories are hypotheses that an experiment can
support, an explanation of why something happens
• Laws are wide-spread observations, they state what happens (not why)
SI Units• Internationally recognized units of measure to
standardize scientific community• Mass – Kilogram (Kg)• Length – Meter (m)• Time – Seconds (s)• Temperature – Kelvin (K) or Celsius (ºC)
Prefixes:
Giga (billion), Mega (million), Kilo (thousand),
Hecto (100), Deka (10), Deci (1/10), Centi (1/100)
Milli (1/1000), Micro (1/million), Nano (1/billion),
Pico (1/trillion)
Accuracy vs. Precision• Accuracy: how close to a target• Precision: how close to each other (consistency)
Uncertainty in Measurements• A. Measurements always have some amount of
uncertainty based on the measuring device
• B. Correct measurements always have one “uncertain number”
Significant Figures• Rules:
1. All non-zero #’s are significant
2. Zeros only significant if between numbers or behind numbers with decimal visible anywhere (202), (0.020), (200.), (200)
3. Exact numbers (obtained from counting or from definitions) (12 in a dozen, 60 min. = 1 hour) have infinite sig. figs.
Sig. Fig. Calculations• Multiplication/Division
Depends on smallest # of sig. figs
Ex. 10.5 x 0.5 = 5.25 which we round to 5 (1 s.f.)
• Addition/Subtraction
Depends on smallest # of decimal spaces
Ex. 10.5 + 0.5 = 11 but we make it 11.0 to have 1 decimal point
Conversions• Use equivalence to compare two units
• Ex. 2000 Centimeters kilometersIf the units match, then you are done, perform the math
Temperature• Fahrenheit scale based on human body temp.
(ºF-32)x (5/9) = ºC
• Celsius scale based on boiling/freezing water ºC x (9/5) + 32 = ºF
• Kelvin scale based on absolute zero (theoretical temp. when motion stops)
ºC + 273 = K
Density• Density = mass/volume
• Usually in grams/cm3 or g/ml
• Depends on compactness of an object
Classification of Matter• Solid: defined shape, little atomic motion• Liquid: shape of container, more atomic
motion, definite volume• Gas: no shape, no volume, easily
compressible, rapid movement
• Homogenous mixture: can’t see separate parts
• Heterogeneous: separate parts can be seen
• Physical change: change in form but not composition (peanuts peanut butter)
• Chemical change: change in composition (burning, rusting, etc.)