Chem Midterm: Definitions

Scientific Law

A (usually mathematical) summarization of an observable behavior.

A unifying concept underlying a natural phenomenon based on experiments and/or observations.

Scientific Theory

AKA Model.

a scientifically acceptable general principle used as a predictive model for the results of testing hypotheses

Compound

A combination of 2+ elements

Solution

A homogenous mixture composed of 2+ substances

Element

A chemical substance w/ only 1 type of atom present

Mixture

A mixture containing 2+ substances, elements, and/or compounds that are only physically joined

Physical Properties

properties observable w/o altering the identity and composition of the substance

ex. color, odor, density, hardness and melting/boiling point

Chemical Properties

properties that are observable by changing the substance or reacting the substance w/ others to form different substances

ex. flammability (burning in the presence of oxygen)

Intensive Properties

properties that do NOT depend on the amt. of substance present

ex. density, boiling point, temperature

Extensive Properties

properties that DO depend on the amt. of sample present

ex. volume, mass, length

Celsius to Kelvin

C + 273 = K

Celsius to Fahrenheit

9/5(C) + 32 = F

Kilograms to Pounds

1 kg = 2.205 lbs

Kilometers to Miles

1.6093 km = 1 mi

Centimeters to Inches

2.54 cm = 1 in

Dalton’s Atomic Theory Hypothesis

1. Each element is composed of extremely small particles called atoms.

2. All atoms of a given element are identical BUT different from another elements (wrong b/c isotopes)

3. Atoms are neither created or destroyed in chemical reactions (turns into Law of Conservation of Mass).

4. Each compound ALWAYS has the same relative number of atoms (turns into Law of Constant Composition → Law of Multiple Proportions)

Atom

the smallest representative particle of an element.

infinitesimally small building blocks

Millikan Oil Drop Experiment

Determined the charge of an electron (and proton)

-1.602×10^-19 C

Cathode Rays

Composed of electrons regardless of metal used.

J.J. Thompson vs Rutherford Atom Model

T: Plum Pudding
+ charged sphere. - charged electrons scattered throughout

R: Nuclear Model
+ charged, densely packed nucleus. - charged electrons orbit
nucleus comprised of + charged protons & = charged neutrons

Atomic Number vs. Mass number

A: proton #. determines element (and electron #)

M: proton + neutron #. determines mass (amu) / isotope

Mass Spectrometer

Determines atomic weights via atoms/molecules as a gas

Gas → cations → deflect from charged grid → different angle of deflection based on mass of atom/molecule

PT: Groups

Columns

Elements that exhibit similar properties

1A/1 = Alkali Metals, 2A/2 = Alkaline Earth Metals

7A /17= Halogens, 8A/18 = Noble Gases

PT: Periods

Rows

Metals vs Nonmetals vs Metalloids

Metals: left of the stair case. luster, high electrical and heat conductivity, solid at room temp. (except Mercury)

Nonmetals: right of the staircase. primarily liquids and gases w/ heavy variation in appearance and physical properties

Metalloids: hug left of staircase. share properties of metals and nonmetals

Molecular vs Empirical vs Structural Formula

M: actual count of each atom # in a molecule

E: relative count of each atom# to each other

S: depicts connections of atoms, lacking in previous

Polyatomic ion

atoms joined as a molecule that care a + / - charge

Ionic Compounds

Compound formed from anions(-. usually nonmetals or polyatomic) and cations (+. usually metals)

Naming: Cations

Named after used element/molecules name

For metals w/ varying ions, use roman numerals to determine charge

Naming: Anions

elemental name + -ide

Naming: Oxyanions

Polyatomic anions w. oxygen

element + suffix

-ate = normal O count. per + element + ate = 1 extra O

-ite = 1 less O count. hypo + element + ite = 2 less O

Naming: Acids

elements: hydro + element + ic

oxyanions w/ -ate: (per +) element + ic

oxyanions w/ ite: (hypo +) element + ous

Naming: Binary Molecular Compounds

1. 2 nonmetal elements ordered left & top most element first

2. Second element has suffix -ide

3. Each element w/ roman # prefix (except mono- for first element)

PT: Atomic Mass

average amu of all naturally ocurring isotopes of an element

Stoichiometry

the study of quantities of substances consumed and produced in chemical reactions

Combination vs Decomposition vs Combustion Reactions

2+ Reactants → 1 Product

1 Reactant → 2+ Product

Hydrocarbon + O2 → A*CO2 + B*H2O

Formula vs Molecular Weight

FW: sum of atomic weights of the atoms in the chemical formula

MW: FW of a molecule

Percentage Composition

percent by mass contributed by each element in the substance

% comp. = (atom count) x (atom amu) / (substance FW)

Mole

the amt. of matter that contains as many objects as the number of atoms in exactly 12 g of isotopically pure carbon-12

Avogadro’s # = 6.022×10²³

Molar Mass

mass in grams of 1 mol of a substance

molar mass = grams per mol = amu

Combustion Analysis

Given amt. of substance burned & CO2 and H2O made

1. Determine grams of each element in the sample

2. Determine the mol. of each element w/ the mass

3. Ratio each element’s mol. to the nearest integer to determine the substance chemical formula.

Single vs Double Displacement/ Exchange Reaction

S: AX + B → A + BX

D: AX + BY → AY + BX

Limiting vs. Excess Reactant

L: a reactant that is completely consumed in a reaction

E: reactants remaining in a reaction

Solution vs Solvent vs Solute

1. homogenous mixture of 2+ substances

2. substance of greatest quantity in a solution

3. other substances in a solution

Why is water good at dissolving ionic compounds?

Water is a polar molecule, where one side is positively charged and the other is negatively charged.

ionic compounds split into cations and anions and attach to the oppositely charged side of the water molecule

Immiscible vs Partly vs Miscible compounds

I: Compounds that don’t mix and form separate layers

P: Compounds that can mix under certain conditions but don’t when they are not met. mix “ish”

M: Compounds that mix together to form a single layer

Strong vs Weak Electrolytes

S: Solutes in aq. that exist completely as ions. single arrow

W: solutes in aq. that exist as mostly neutral molecules. double arrow

Complete vs. Net ionic Equation

C: eq. that indicates which molecules exist as ions

N: eq. that indicates only the ions that are actual reactant participants in the reaction

Acid vs Base

A: substances that ionize in aq. to form H+ ions

• “proton donors” (b/c H+ is a proton w/o a electron)

B: substances that ionize in aq. to form OH- ions

Aqueous State (aq.)

When a molecule is in a solution where water is the solvent

Mono vs Diprotic Acids

Prefix + protic

Numeric prefix determines amount of H+ ions present in the acid

Strong vs. Weak Acids/Bases

electrolyte strength determines acid/base strength and vice versa

Salt

An ionic compound whose cation is from a base and anion is from an acid

Neutralization Reaction

Acid + Base → Water + Salt

Redox Reactions

AKA Oxidation(lose electrons) - Reduction(gain electrons) Reactions

Reaction where electrons transfer from 1 reactant to another

Oxidation Number

Assigned to each atom/ion to keep track of electron transfer

1. Atoms in element form: ox # = 0

2. Ions: ox # = ionic charge

3. Nonmetals: oxidations # usually < 0

4. Sum of ox # = 0 for neutral compound/

Activity Series

metals arranged in order of decreasing easy of oxidations

any metal can be oxidized by ions below it

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Concentration

quantity of solute present in a given quantity of solvent/solution

more solute = higher concnetration

Molarity

M. concentration of a solution as moles of solute per liter of solution

Dilution

the reduction of concentration of solution by adding water

volume grows BUT moles of solute remain unchanged

(Mconc) x (Vconc) = (Mdil) x (Vdil)

Titration

Process of reacting a solution of unknown concentration w/ one of known concentration (standard solution)

Equivalence point

Point at which the stoichiometrically equivalent quantities are brought together

center/vertical part of th S-shaped graph

Precipitate

Insoluble Products in a Aq. Solution

Chemistry

the study of the composition, structure, properties and changes in matter

Solid vs Liquid vs Gas

S: Fixed Shape and Volume

L: Fixed Volume. Loose Shape

G: Loose Shape and Volume

Matter Diagram

Matter: Occupies Space and Possesses Mass

1. Pure Substance: invariant chemical composition

   1. Element: Fundamental substance. cannot be separated into simpler substances

   2. Compound: Substance composed of 2+ elements in fixed proportions.

2. Mixture: 2+ pure substances retaining individual identities. separatable by physical methods

   1. Homogenous: uniform composition and properties

   2. Heterogenous: not uniform comp. or prop.

Discovery of Atom Diagram

J.J. Thomson: cathode ray = charged particle = electron

• “Plum-Pudding” model of atom

• Millikan: charge and mass of electron

Rutherford: Alpha, Beta and Gamma Particles

• Nuclear Model of atom

• Proton

• Chadwick: Neutron

Angstrom

used to describe dimension of atoms

1 angstrom = 100 picometers = 10^-10 meters