Chemistry - Part A

Page 1

Scientific Method:

Science can be: ( Ten Pretty Elephants Talk Roman)

Testable

Predictive

Explanatory

Tentative

Reproducible

Scientific Method:

1. Make an observation

2. Form a hypothesis

3. Gather Data from experiment

4. Develop Theories and Laws

Matter: made up of atoms and molecules

- Substances: Matter that has definite composition (Chemical); molecules of same composition and structure

Elements

Compounds

- Mixtures: A physical blend of two or more pure substances in any proportion in which each substance retains its individual properties; can be separated by physical means.

Homogeneous

Heterogeneous

Measurements:

Length ( Meter)

Mass ( kilograms)

Time (seconds)

Temperature (Kelvin)

Amount of substance ( moles)

Electrical Current ( Ampheres)

Luminous Intensity (Candela)

Common SI Prefixes:

10^12 Tera

10^ 9 Giga

10^6 Mega

10^3 Kilo

10^2 Hecto

10^1 Deca

10^-1 Deci

10^-2 Centi

10^-3 Milli

10^-6 Micro

10^-9 Nano

10^-12 Pico

SIG FIGS

(1) All nonzero digits are significant: 1.234 g has 4 significant figures, 1.2 g has 2 significant figures.

(2) Zeroes between nonzero digits are significant: 1002 kg has 4 significant figures, 3.07 mL has 3 significant figures.

(3) Zeroes to the left of the first nonzero digits are not significant; such zeroes merely indicate the position of the decimal point: 0.001o C has only 1 significant figure, 0.012 g has 2 significant figures.

(4) Zeroes to the right of a decimal point in a number are significant: 0.023 mL has 2 significant figures, 0.200 g has 3 significant figures.

(5) When a number ends in zeroes that are not to the right of a decimal point, the zeroes are not necessarily significant

WHEN ADDING:

1. RESULTING NUMBER SHOULD HAVE SAME NUMBER OF DECIMAL PLACES AS NUMBER WITH FEWEST DECIMAL PLACES.

WHEN MULTIPLYING AND DIVIDING:

1. RESULTING NUMBER SHOULD HAVE SAME NUMBER OF SIGNIFICANT FIGURES AS NUMBER WITH FEWEST DECIMAL PLACES.

OTHER CONVERSIONS:

1kg = 2.205 lb

1 lb = 453.6 g

1 oz = 28.35 g

1 m = 39.37 in

1 km = 0.6214 mi

1 in = 2.54 cm

1 L = 1.057 qt

1 gal = 3.785 L

1 fl oz = 29.57 mL

Page 2

AP Chemistry: Chapter 2

Conservation of mass: the total mass remains same after any chemical reaction

Law of Definite Proportions: All samples of a compound have the same composition; all samples have the same proportions, by mass, in a compound

Law of Multiple Proportions: When two or more different compounds of the same two elements are compared, the masses of one element that combine with the a fixed mass of the second element are in the ratio of small whole numbers.

Dalton's Theory:

All matter is composed of extremely small, indivisible particles called atoms

All atoms of a given element are alike in mass and other properties, but atoms of one element differ from the atoms of every other element

Compounds are formed when atoms of different elements unite in fixed proportions

A chemical reaction involves a rearrangement of atoms. No atoms are created, destroyed, or broken apart in a chemical reaction

Atoms that have the same number of protons but different numbers of neutrons are called isotopes

Mass Spectrometer: Only tool that can measure atomic mass accurately.

Atomic Mass Unit : one-twelfth the mass of a carbon-12 atom

The atomic mass of an element is the weighted average of the masses of the naturally occurring isotopes of that element

Weighted average means you multiply the weight by the % abundance.

PERCENTAGE ABUNDANCE: example problem

�14.003074X + 15.00018(1-x) = 14.0067

�14.003074X + 15.000108-15.000108X = 14.0067

�X = -0.9934/-0.997034 = 0.9964

�14N= 99.64%

�15N = 1-99.64= 0.36%