General Chemistry placement test Study Guide

molecule

two nonmetal atoms combined form a covalent compound called a

diatomic molecules

H2,O2,F2

Matter

Anything that has mass and takes up space

Element

A substance that cannot be broken down into simpler substances

Compound

A pure substance made of two or more elements CHEMICALLY combined.

Compound

Can be decomposed by chemically

Mixture

A PHYSICAL blend of two or more components

(aq)

aqueous mixture, a substance is dissolved in water

homogeneous mixture

A mixture that is so evenly mixed that you can't see all of the different parts. Ex. Air, kool-aid

heterogeneous mixture

A mixture in which different materials can be seen easily.

Ex. soil, chocolate chip cookies

filtration

process to separate a solid "precipitate" from a liquid

sublimation

phase change from (s) --> (g)

empirical formula

A formula showing the lowest whole number ratio of atoms in a compound. Can't be reduced.

solid

A state of matter that has a definite shape and a definite volume

liquid

A form of matter that flows, has constant volume, and takes the shape of its container

Bromine (Br) and Mercury (Hg)

only two liquids on the periodic table

gas

A state of matter with no definite shape or volume

gas

will uniformly and completely fill a container

gases

physical property most all nonmetals and group 18

physical property

A characteristic of a substance that does not involve a chemical change. Ex. melting/boiling point, solubility, density, color, or hardness.

properties

used to identify or recognize matter (objects).

chemical property

describes how matter reacts when it changes chemically into another substances. Ex. reactivity with acid, base or with air to rust, flammability, decomposition.

physical/phase change

(s)-->(l)-->(g), diluting, crush, cut. Still same substance.

Density

A physical property. Specific to every element.

Chemical symbol

One capital letter, or a capital letter and a lower case letter together. Mass on upper left side, and atomic # on lower left side.

Conservation of Mass

Equal # of atoms on both sides of a chemical equation

Democritus

Greek philosopher that said all matter is made of tiny particles called "atomos" or atoms

JJ Thomson

used the cathode ray tube to discover electrons

Rutherford

Gold foil experiment: (atom is mostly empty space, atoms contains a dense, positively charged nucleus); discovered protons.

Wave Mechanical Model

Modern model of the atom, atoms have electrons in "orbitals" that are like clouds around the nucleus

Bohr Model

A model resembling planets revolving around the sun in orbits, useful in visualizing the structure of atoms.

Proton

A subatomic particle that has a positive charge and that is found in the nucleus of an atom. Mass = 1 amu

Atomic number

Equals the number of protons in the nucleus (never changes)

Electron

A tiny, negatively charged particle that moves around the nucleus of an atom.

# of protons

Equals # of electrons in a neutral atom

Nucleus

A region that is located at the center of an atom and contains most of the atom's mass (protons and neutrons)

Neutrons

neutral partical that has the same mass as a proton and is found in an atom's nucleus.

Isotopes

Atoms of the same element having different masses because they contain different numbers of neutrons.

Principle Energy Levels

energy levels of an atom "shells". Energy increases further from the nucleus

valence electrons

Electrons on the outermost energy level of an atom

Lewis dot structures

diagrams that show valence electrons as dots

Bright line spectrum

colors produced when electrons fall to a lower energy level and release energy in the form of light.

Ions

Atom or group of atoms(polyatomic) with a positive or negative electrical charge due to a loss or gain of electrons. Ex: Na+, Cl- , NO3-

Mendeleev

Created the first periodic table. Arranged elements by increasing atomic mass

Modern Periodic Table

elements are arranged in order of increasing ATOMIC NUMBER

Groups of Periodic Table

Columns represent elements that have the same number of valence electrons and share similar chemical and physical properties

Periods of periodic Table

Rows correspond with # of total principle energy levels "shells" (rings)

Ionization Energy (IE)

Energy required to remove an electron from an atom

Electronegativity (EN)

Atom's ability to attract and hold electrons.

Metals

malleable (made into thin sheets) and lustrous (shiny)

good conductors of electricity and heat.

Low IE and Low EN

Metals

High IE and High EN

Nonmetals

Nonmetals

Elements that are poor conductors of heat and electric current. Most are gases, dull & brittle

Metalloids

Elements along the staircase. Have properties of both metals and nonmetals. Ex: Silicon

Alkali Metals

Group 1 on PT. One valence electron that is easily removed to form a POSITIVE IONS. Highly reactive and form stable compounds.

Alkali Earth Metals

Group 2 on PT. Two valence electrons, form +2 ions. reactive

Halogens

Group 17: Nonmetals 7 valence electrons in it's outermost shell.

Very reactive. Many diatomic gases and Iodine solid

Noble Gases

Group 18: Nonreactive family of nonmetals; 8 valence e- (full octet). All are gases at room temp.

Transition Metals

Form colored ions in solution. Have multiple oxidation states

Cation

An atom that lost electrons and therefore has a positive charge. Metals lose electrons

Anion

An atom that gained electrons and therefore has a negative charge. Nonmetals gain electrons

Ionic Compound

Composed of metal cations and non-metal anion, also known as a salt. Conducts electricity in solution (aq)

High melting points

Ionic Bond

a chemical bond in which a METAL atom loses an electron to form a positive cation and a NONMETAL atom gains an electron to form a negative anion.

"electrons are transferred"

Writing Ionic compounds

Write each element with their charge and CROSS & DROP numbers ONLY. Ex: Ca+2 Cl-1 --> CaCl2 *metal always is first.

Writing Covalent/Molecular Substances

Both nonmetals use prefixes to tell # of atoms of each element. (mono, di, tri, tetra)

Covalent/Molecular Bond

chemical bond formed when 2 atoms share electrons NONMETAL to NONMETAL

Ideal gas

HIGH Temp & LOW Pressure

Collision Theory

For a reaction to occur, the particles must collide with the appropriate orientation, and sufficient energy.

Gas Laws: Volume-Pressure

If V increases, P decreases and If V decreases, P increases

"Marshmallow man"

Gas Laws: Volume-Temperture

If V increases, T increases, and If V decrease, T decreases

"soap souffle"

Combined gas law

P1V1/T1 = P2V2/T2 Temp always in K

STP = standard temp (273 K) and standard pressure (1 atm or 101.3 kPa)

Avogadro's Hypothesis

EQUAL VOLUMES of any gases at the same temperature and pressure contain EQUAL # OF MOLECULES

Making a Bond

Exothermic; Energy is released (energy is a product)

Ex: Cl + Cl --> Cl2 + 242 kJ

*more energy released the more stable the bond

Breaking a Bond

Endothermic; Energy is absorbed (energy is a reactant)

Ex: H20 + 571 kJ --> H2 + O2

Exothermic reaction

A chemical reaction that RELEASES energy as a product

Negative delta H (heat of reaction) "hot to touch"

Endothermic reaction

A reaction that ABSORBS energy in the form of heat.

Positive delta H (heat of reaction) "cold to touch"

Atomic Radius

Size of the atom. Increases in size from more shells or if atom gains electrons (anion). Decreases in size if atom loses electrons (cation) or less shells.

Polar bonds and Polar molecules

Uneven sharing of electrons causes a nonsymmetrical shape. EN # difference between atoms is above 0

Ex: WATER

Nonpolar bonds and nonpolar molecules

EN # difference between elements = 0 Ex: diatomics

Molecules have even distribution of charges and are symmetrical.

Network Solids

a solid in which all of the atoms are covalently bonded to each other. C-C-C-C "diamonds"

Metallic Bonds

A "sea of mobile electrons" surrounding positive metal ions

Ex: metal to metal Cu-Cu-Cu-Cu

Soluble

capable of being dissolved in some solvent (usually water)

Factors that effect solubility

Increase in Temp, stirring, & particle size (increased surface area) will all increase solubility and increase rate of reaction.

Colligative Properties

The more particles that are produced when a substance dissolves, the higher the BP and the lower the FP will be produced. Ex: *NaCl = 2 particles (Na+, Cl-)

*CaCl2 = 3 particles (Ca+, Cl-, Cl-)

Average Kinetic Energy

is directly proportional to temperature.

Highest Avg KE = Highest Temp

Heat of Reaction

The difference in energy between the PE of the reactants and PE of the products of a chemical reaction.

Activation Energy

Energy required to initiate both Exothermic and Endothermic reactions.

Catalyst

Lowers the activation energy needed to get a reaction started.

Vapor Pressure Table H

Dotted line represents the boiling point of the 4 liquids at Standard Pressure of 101.3 kPa

Organic Chemistry

Study of all chemicals containing carbon

Saturated hydrocarbon

All of the bonds are single bonds

Unsaturated hydrocarbon

Contain carbon-to-carbon double or triple bonds.

Alkane

a hydrocarbon containing only single covalent bonds

Alkene

A hydrocarbon that contains a double bond.

Alkyne

a carbon compound with a carbon-carbon triple bond.

Methyl Group

-CH3

Ethyl Group

-C2H5

Organic Alcohol

contain OH functional group; ethanol, methanol

Organic Aldehydes

contain CHO functional group: ends in "al"

Ketones

contain C- (C double bond O)- C functional group:

ends in "one"