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.)