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 x 0.5 = 5.25 which we round to 5 (1 s.f.) Addition/Subtraction Depends on smallest # of decimal spaces Ex = 11 but we make it 11.0 to have 1 decimal point

Conversions Use equivalence to compare two units Ex Centimeters  kilometers If 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 = K

Density Density = mass/volume Usually in grams/cm 3 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.)