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anything that has mass and occupies space


two things loosely joined together


a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight


the study of composition, structure, properties and reactions of matter


substance that always has the same composition and properties wherever it is found

scientific method

observations, hypothesis, experiment, theory

measured numbers

the numbers you obtain when you measure a quantity

exact numbers

those obtained by counting items or from a definition that compares two units in the same measuring system


The ability to do work


any activity that requires energy

Potential energy

stored energy. Types: gravitational, chemical, electrostatic

Kinetic energy

the energy of motion. types: mechanical, thermal, electrical


energy that flows from a warmer object to a cooler one


SI unit of energy and work


amount of energy needed to raise the temperature of 1g of water by 1 degree Celsius


how hot or cold a substance is compared to another substance


1.8*(temperature Celsius) + 32

Specific heat

amount of heat needed to raise the temperature of exactly 1g of substance by exactly 1 degree Celsius

Pure substance

matter that has a definite composition


the simplest pure substance, contains only one material


a pure substance that contains 2 or more elements all in the same proportions


two or more substances that are physically mixed but not chemically combined

homogeneous mixture, solution

composition is uniform

heterogeneous mixture

mixture where composition is not uniform

physical properties

characteristics that can be observed without affecting the identity of a substance

physical change

change of a substance where its state or apperance will change but its composition remains the same

chemical properties

properties that describe the ability of a substance to change into a new substance

chemical changes

changes in a substance where the substance is converted into one or more new substances in which have different chemical and physical properties

Heat of fusion

energy needed to separate particles of a solid during melting

Heat of fusion for water

334 Joules = 80 calories for 1g of H2O

Heat needed to melt

mass * heat of fusion

heat of sublimation for water

2590 J = 620 calories for 1 gram of H2O

Heat of vaporization for water

2260 Joules = 540 calories for 1g of H2O

Heat needed to vaporize or condense

mass * heat of vaporization

Heat of a reaction

heat of products minus heat of reactants

representative elements

an element in an "A" group in the periodic table; as a group these elements display a wide range of physical and chemical properties. In their atoms, the s and p sublevels in the highest occupied energy level are partially filled

transition elements

groups of elements in the modern periodic table that are designated with a B(1B through 8B) and are further divided into transition metals and inner transition metals

alkali metals

Group 1, 1 electron in outer level, very reactive, soft, silver, shiny, low density; Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

alkaline earth metals

metallic elements in group 2 of the periodic table which are harder than the alkali metals and are also less reactive

noble gasses

non-metals, group 18, the most non-reactive elements


semiconductors, border the zigzag line, shiny, brittle, hard, at high temp- good conductors of electric current


left of the zigzag line, shiny, malleable, ductile, good conductors of electric current, good conductors of thermal energy


elements that are usually dull in appearance, poor conductors of heat and electricity, gases at room temperature


group 17; contains nonmetals; 7 electrons in its outermost energy level; very reactive; poor conductors of electric current; never in its uncombined form in nature; combine with most metals to form salts


smallest particle of an element that retains the characteristics of that element

subatomic particles

smaller bits of matter that atoms are composed of


negatively charged particles in an atom


positively charged particles in an atom


where protons are contained in the atom


a particle contained in the nucleus of the atom, it is neutral

proton mass

1.7*10^-24 g (also about the mass of a neutron)

electron mass

9.1*10^-28 g, 1/1800 of H atom

atomic mass unit (amu)

one twelfth of the mass of a carbon atom with six protons and six neutrons


1 amu


1 amu

atomic number

# of protons in an atom

mass number

protons + neutrons


atoms of the same element that have different numbers of neutrons

atomic mass

the weighted average of all the naturally occurring isotopes of that element

atomic spectrum

the spectrum created when the light emitted from a heated element is passed through a prism


levels within each energy level that contain electrons with identical energy


a region in an atom where there is the highest probability of finding an electron, they are sub-shells of the n shells, each orbital can have a max of 2 electrons. orbitals with the same value of n form a shell, and orbitals on the same energy level are called degenerate

atomic radius

distance from nucleus to the valance electrons

ionization energy

the energy needed to remove the least tightly bounded electron from an atom in the gaseous state

cathode ray tubes

ray moves with electric and magnetic field, made of particles

alpha particle

2 protons, 2 neutrons, mass number of four, atomic number of 2, charge of 2+

beta particle

high energy electron that is emitted when a neutron in an unstable nucleus changes to a proton charge of 1-, mass number of 0

positron particle

produced by an unstable nucleus when a proton is transformed into a neutron and a positron. positive 1+ charge, mass number of 0, (B+) antimatter


an isotope that emmitts radiation


a particle that is the exact opposite of another particle

Gamma rays

high-energy radiation, released when an unstable nucleus undergoes a rearrangement of its particles to give a more stable, low energy nucleus. Gamma rays are often emitted along with other types of radiation. No mass or charge

Radioactive decay

when a nucleus spontaneously breaks down by emitting radiation


converting stable, non-radioactive isotopes into radioactive ones by bombarding the nucleus by high speed particles to produce radioisotopes


3.7*10^10 disintegrations per second


1 disintegration per second

radiation absorbed dose (rad)

measures amount of radiation absorbed by a gram of material

Gray (Gy)

100 rads

radiation equivalent in humans (rem)

measures biological effects of different kinds of radiation. rem = rad x factor

sivert (sv)

100 rems


the amount of time it takes for one half of a sample to decay

decay curve

diagram of the decay of a radioactive isotope


smallest quanta of electromagnetic radiation

atomic energy

energy generated when splitting an atom

nuclear fission

splitting the nucleus of an atom

chain reaction

the rapid increase in number of high-energy neutrons capable of splitting

Nuclear fusion

2 small nuclei combine to form a larger nucleus. Mass is lost and energy is released. fusion happens in the sun, requires 100,000,000 degree Celsius

mass of substance left after a certain amount of time

mass * (.5)^(how many half lives have passed)

ground state

the lowest energy state of an atom

excited state

an electron moves up a level


period number

the number of electrons allowed in an energy level


octet rule

the tendency for atoms to attain a noble gas electron configuration

ionic compound

a compound where an atom of one element lose valance electrons and the atoms of the other element gain valance electrons. electrolytes (ions dissolve in solution) metal + nonmetal, cation + anion, polar, conductive in solute or melted

covalant compound

a bond between elements where the elements share valance electrons. no electrolytes, do not conduct, no ions, two nonmetals, compounds do not break when dissolved


an atom or group of atoms having an electrical charge because of a loss or gain of electrons. formed in ionic bonding


positively charged ions formed when metals in ionic compounds lose their valance electrons, named by the element


negatively charged ions formed when nonmetals in ionic compounds gain valance electrons from metals, named with an ide

volume of ions

much smaller for metals and larger for nonmetals

polyatomic ion

a group of atoms that has an ionic charge. most are nonmetal covalent bonds with oxygen. generally stick together and behave as if it were one atom

covalent compound

what is formed when atoms of two nonmetals achieve stability by sharing electrons (creates a covalent bond)


what is formed when two or more atoms share electrons

resonance structures

when two or more electron-dot formulas can be written for a compound

Naming covalent compounds

1st nonmetal: element name
2nd nonmetal: prefix-name-ide

Covalent prefixes

mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca


the attraction of an atom for valence electrons in a chemical bond

nonpolar covalent bond

a bond between atoms with identical or very similar electronegativity values

polar covalent bond

when shared electrons are unequal in electronegativity


a polar covalent bond that has a separation of charges +----> indicates a dipole

valence-shell electron-pair repulsion (VSEPR) theory

indicates that the electron groups will move asw far apart as possible to reduce repulsion between the negative charges


180 degrees


120 degrees

Trigonal Planar

120 degrees

Tetrahedral (pyramid)

109.5 degrees

Trigonal pyramidal

107 degrees

bent (3-D)

105 degrees

polar molecule

one end of the molecule is more negatively charged than another end

dipole-dipole attractions

attractive forces that occur between the positive end of one molecule and the negative end of another

hydrogen bond

a strong dipole-dipole attraction between polar molecules created when a hydrogen atom is attached to fluorine, oxygen or nitrogen

dispersion forces

very weak attractions that occur between nonpolar molecules


atoms in the reacting substances in a chemical reaction


results of a reaction

chemical reaction

the process by which a chemical change takes place

chemical equation

a shorthand way to represent a chemical reaction using chemical formulas to indicate the reactants, products and coefficients to show reacting ratios

balanced equation

the final form of a chemical equation that shows the same number of atoms of each element in the reactants and products

combination reaction

a reaction in which reactants combine to form a single product

decomposition reaction

a reaction in which a single reactant splits into two or more simpler substances

single replacement reaction

a reaction in which an element replaces a different element in a compound

double replacement reaction

a reaction in which parts of two different reactants exchange places


a group of atoms, molecules or formula units that contain 6.02x10^23 of these items. One mole of any element always contains Avogadro's number of atoms

Avogadro's number

the number of items in a mole; equal to 6.02x10^23

formula units

the group of ions represented by the formula of an ionic compound

molar mass

the mass in grams of one mole of an element equal numerically to its atomic mass. The molar mass of a compound is equal to the sum of the masses of the elements in the formula

mole-mole factors

a conversion factor that relates the number of moles of two compounds derived from the coefficients in an equation

theoretical yield

the maximum amount of product that a reaction can produce from a given reactant

actual yield

actual amount of product produced by a reaction

percent yield

the ratio of the actual yield of a reaction to the theoretical yield possible multiplied by 100%

Bonding (intramolecular) forces

covalent(sharing electrons), ionic(loosing, gaining electrons)

Attractive (intermolecular) forces

hydrogen, dipole-dipole, dispersion

limiting reactants

the reactant used up during a chemical reaction-it limits the amount of product that can form

excess reactant

the reactant that remains when the limiting reactant is used up in a reaction

Exothermic reaction

a reaction that releases energy in the form of heat

endothermic reaction

A reaction that ABSORBS energy in the form of heat

activation energy

the minimum amount of energy required to start a chemical reaction

heat of reaction

the quantity of energy released or absorbed as heat during a chemical reaction. each product/reactant = moles*heat of formation

oxidation (OIL)

the loss of electrons by a substance. Biological oxidation may involve the addition of oxygen or loss of hydrogen

oxidation/reduction reaction

a reaction in which the oxidation of one reactant is always accompanied by the reduction of another reactant. Provides us with energy from food, provides electrical energy in batteries, occurs when iron rusts, transfer electrons from one reactant to another

reduction (RIG)

the gain of electrons by a substance. Biological reduction may involve the loss of oxygen or gain of hydrogen

Heat of formation

the amount of heat required to form a substance

activated complex

a high energy transitional structure in a chemical reaction where old bonds are breaking and new bonds are forming

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