Principles of Chemistry I

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Macroscopic
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properties and behavior we can see (ex. color, flammibility, volume, mass)
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submicroscopic
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properties and behavior we can not see (ex. atoms, molecules, chemical bonds)
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Extensive Properties
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dependent on amount of sample (mass, volume)
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Intensive Properties
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independent of amount of sample; some can be used to identify substances

 (temp, density, gas pressure, melting point)

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SI Units
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length = meter (m) mass = kilogram (kg) time = second (s) amt of substance = mole (mol) temp = kelvin (K) electic current = ampere (A) luminous intensity = candela (cd)
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Celsius to Kelvin
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C = K – 273.15
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Celsius to Fahrenheit
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F = 1.8C + 32
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Fahrenheit to Celsius
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C = .56 (F-32)
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Accuracy
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How closely a measurement agrees with a true value
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Precision
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How closely individual measurements agree with each other
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Systematic Error
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a constant error that affects all measurements the same
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Random Error
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a variable error that affects each measurement differently
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Significant Figures in Addition and Subtraction
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The answer has the same number of decimal places as the measurement with the fewest decimal places 89.5 + 45.25 + .123 = 134.9
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Significant Figures with Multiplication and Division
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The answer contains the same amount of significant figures as the measurement with the fewest significant figures 12.25 + .256 + 23 = 72
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Isotopes
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atoms with the same number of protons, but different numbers of neutrons.
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Atomic number (Z)
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the number of protons or electrons(defines atom)
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Mass number (A)
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the number of protons + neutrons
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Atomic mass
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mass of a single atom in atomic mass units (amu)
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Molecular mass
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mass of a single molecule in atomic mass units (amu) 

 the sum of the atomic masses of each atom in a molecule

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Formula Unit mass
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the mass of all of the atoms in a formula unit in amu
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Empirical formula
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shows the simplest integer ratio of atoms of each element in a compound.
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Molecular formula
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shows the number of atoms of each element in a molecule.
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Structural formula
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shows the connectivity of the atoms in a molecule.
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Matter
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the physical material of the universe (has mass and occupies space)
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Atom
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the building block of matter
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What determines the properties of matter?

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Composition- which atoms?

Structure- how are atoms connected?

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What do we do in Chemistry?
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Attempt to understand the properties and behavior of matter by studying the properties and behavior of atoms and molecules
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Gas
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no fixed volume or shape

confomrs to volume and shape of container

particles far apart and moving rapidly

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Liquid
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distinct volume but no shape

assumes shape of portion of container it occupies

particles packe close together and moving rapidly (can be poured)

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Solid
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distinct shape and volume

particles held tightly together with little movement

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Pure Substance
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Matter with distinct properties and constant composition

Can be either

-element

-compound

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Mixture
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Combination of 2+ pure substance

Relative amts of components can vary

Each component retains its own properties

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Homogeneous and Heterogeneous Mixtures
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homo- composition of same materials (solution)

hetero- composition of different materials

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Physical Properties
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Observe without changing the identity or composition of a substance

(color, density, melting point, boiling point)

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Chemical Properties
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Describe the way a substance may change or react to form other substances

(flammability)

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Physical Change
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1. Substance changes physical appearance but not composition

2. Changes of state are physical changes

(melting ice)

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Chemical Change
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1. Substance is transformed into a different substance

2. Called a chemical reaction

(hydrogen burns in air to form water)

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Democritus

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Found matter is particulate or made of particles rather than continuous mass.
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Dalton’s Atomic Theory

(Postulates)

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1. All matter consists of tiny indivisible atoms.

2. Atoms of an element are identical, but different from those of other elements.

3. Atoms of one element cannot be converted into those of another element.

4. Compounds result from chemical combinations of different elements; atom ratios are integers.

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Law of Conservation of Mass
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Total mass of materials present after a chemical reaction is the same as the total mass present before the reaction.

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Law of Constant Composition
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Whether in Ankeny or Anchorage, water contains 11.19% hydrogen and 88.81% oxygen by mass.

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Law of Multiple Proportions
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If 2 elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers.
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Are Dalton’s Postulates always true?

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1. Nuclear fission does divide atoms.

2. Nuclear transmutations do change atoms of one element into those of another.

3. Atoms of an element are not identical.

4. Nonstoichiometric compounds sometimes appear to have non-integer atom formulas/ratios.

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J.J. Thomson
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English physicist won nobel prize in 1906.

Worked with Cathode rays.

Measured the charge-to-mass ration of the electron

(1.76×10^8 C/g)

Credited for the discovery of electrons

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Cathode rays
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Independent of the electrode material (different metals create the same results)

Are streams of negatively charged particles (electrons)

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Robert Millikan
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American pysicist

"Oil-drop" experiment

Caused oil drops to become charged and observed their behavior in an electric field.  This led to the charge on the electron= 1.602×10^-19 C

Given charge to mass ration he computed electron mass to be 9.1×10^-28 g

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Plum-Pudding Model of the Atom
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1. Evenly distribute mass and positive chare (cookie)

2. Small embedded negative particles (chocolate chips)

 Disproved by Rutherford’s Gold-Foil Experiment in 1910

;

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Ernest Rutherford
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New Zealand physicist; Father of nuclear physics

Discovered the nature of radioactivity

Explained the phenomenon of radioactivity (spontaneous emission from uranium compounds)

;Gold-Foil; Experiment

Discovered protons in 1919

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Gold Foil Experiment
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Studied angles at which alpha particles were scattered after passing through thin gold foil.

This experiment disproved the plum-pudding model of the atom

Alpha Rays- particles; electrons

Beta rays- particles; protons

Gamma rays- non-particles; nuetrons

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Rutherford’s Nuclear Atom
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a small, very dense, positive nucleus

surrounded by negative electrons

atom diameters:~100-500 pm

nuclei diameters:~10^-2 pm

ratio= 10,000 : 1

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Chadwick
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Discovered neutrons in 1932
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Periodic Table

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Rows= periods

Columns = groups

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Alkali metals

(1A)

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Li,Na,K,Rb,Cs,Fr
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Alkaline earth metals

(2A)

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Bc,Mg,Ca,Sr,Ba,Ra
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Chalcogens

(6A)

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O,S,Se,Te,Po
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Halogens

(7A)

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F,Cl,Br,I,At

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