Chemistry Key Terms

Matter

anything that has mass and volume

Mass

amount of matter in an object

Volume

amount of space an object takes up

Quantitative Observations

observations that include measurements, quantities, and numerical amounts

Qualitative Observations

observations that do not include measurements or numerical amounts

Physical Property

property that can be measured without changing the chemical identity of the substance

Chemical Property

property that can be measured only by changing the chemical identity of the substance

Physical Change

change that does not alter the chemical identity of a substance

Chemical Change

change that does alter the chemical identity of a substance

Extensive Property

property that depends on the amount of matter in a sample

Intensive property

property that does not depend on the amount of matter in a sample, only on the type/identity of matter

Law of Conservation of Matter

mass/matter cannot be created or destroyed it can only be rearranged into different substances in physical/chemical reactions

Substance

something that cannot be broken down into components through physical means

Element

pure substance of identical atoms

Compound

two or more elements chemically combined together

Mixture

blend of two or more kinds of matter, can be broken down into components through physical methods while retaining identity/properties

Homogenous Mixture

looks the same throughout, one phase

Heterogeneous Mixture

looks different throughout, more than one phase

Density

the ratio of mass to volume in a substance

Relative Density

If material A has a lower density than material B, then it will float. If material A has a higher density than material B, then it will sink

Accurary

the closeness of the measurements to a specific value

Precision

the closeness of the measurements to each other

Law of Definite Proportions

A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample

Law of Multiple Proportions

If two or more different compounds are composed of the same two elements, then the ratio of the mass of the second elements combined with a certain mass of the first element is always a ratio of small whole numbers

(two elements can form more than one compound)

Isotopes

the same type of atom with different masses that have varying numbers of neutrons

Dalton’s Atomic Theory

1. Matter is composed of extremely small particles called atoms

2. Atoms are indivisible and indestructible

3. Atoms of a given element are identical in size, mass, and chemical reactivity

4. Atoms of a specific element are different from those of another element

5. Different atoms combine in simple whole number ratios to form compounds

6. In a chemical reaction, atoms are separated, combined, or rearranged

Transverse Wave

vibration of the wave is perpendicular to the direction of the wave

Longitudinal Wave

vibration of the wave is parallel to the direction of the wave

Origin

baseline of energy

Crest

highpoint of a wave

Trough

lowpoint on a wave

Amplitude

distance from origin to crest/trough

Wavelength

distance between corresponding points on adjacent waves

Frequency

number of waves or cycles per unit of time

Quantum

minimum amount of energy gained or lost by an atom

Photoelectric Effect

when light shines on a metal, electrons can be released. A threshold frequency or wavelength is needed to provide enough energy to eject and electron

Photon

a particle of light

Aufbau Principle

electrons occupy the lowest energy orbital possible to reach a ground state electron configuration

Pauli Exclusion Principle

no two electrons within an atom can have the same four quantum numbers

Hund’s Rule/School Bus Rule

when electrons occupy orbitals of equal/degenerate energy, the electrons do not pair up until they have to pair up

Paramagnetism

atoms with one of more unpaired electrons that are slightly attracted to magnetic fields

Diamagnetism

atoms with no unpaired electrons that are slightly repelled by magentic fields

Valence Electrons

the outermost electrons in an atom

The Periodic Law

physical and chemical properties of the elements are periodic functions of their atomic numbers

Octet Rule

atoms try to react to achieve a noble gas configuration, with eight valence electrons

Cations

positive ions that are generally formed from metals

Anions

negative ions generally formed from nonmetals

Atomic Radius

one-half the distance between the nuclei of identical atoms that are bonded together

Shielding

inner electrons shield the valence electrons by canceling out part of the positive nuclear charge

Ionic Radius

one-half the distance between the nuclei of identical ions

Ionization Energy

the energy needed to remove an electron from a neutral atom of an element

Electron Affinity

the energy change that occurs when an electron is acquired by a neutral atom

Electronegativity

the ability of an atom within a compound to attract electrons to itself

Formula Unit

simplest ratio of elements in an ionic compound

Salt

general term for an ionic compound

Polyatomic Ions

groups of covalently bonded atoms that have a charge over the entire structure

Lattice Energy

energy given off when oppositely charged ions bond

Reactants

substances that we start with

Products

substances that are produced/formed or that we end up with

Synthesis

Two or more reactants combine to form one product

A+B —> AB

Decomposition

One reactant decomposes to form two or more products

AB—> A+B

Combustion

Compound with Carbon and Hydrogen +O2 produces CO2 and H2O

Single Replacement Reaction

One element replaces another element in a compound

A + BC —> B + AC

Double Replacement Reaction

Positive or negative ions in the compounds swap places to form new products

AB + CD —> AD + CB

Redox Reactions

Involve the transfer of electrical energy

Mole

means of counting large quantities of particles

Representative Particles

the smallest pieces of a substance

STP

0 degrees Celsius and 1 atmosphere

Empirical Formulas

the simplest, whole-number ratio of atoms in a compound

Hydrates

chemical complex that incorporates water into the structure

Stoichiometry

the determination of proportions in which elements or compounds react with one another

Limiting Reagent

substance that is totally consumed by the reaction

Excess Reagent

substance that does not completely react in the reaction

Theoretical Yield

maximum amount of product that can be formed

Avogadro’s Law

equal volumes of gases at the same temperature and pressure will contain equal numbers of particles

Assumptions of Kinetic Molecular Theory

1. Gas particles occupy large volumes (take up a lot of space relative to their small sizes)

2. All collisions between particles are elastic collisions (no net loss of kinetic energy)

3. Gas particles are in constant, rapid, and random motion

4. There is no attractive or repulsive force between gas particles

5. Kinetic energy is related to temperature

Dalton’s Law of Partial Pressures

The total pressure of a mixture of gases is equal to the pressure of all of the individual gases added together

Boyle’s Law

At a constant temperature, as pressure increases volume decreases. As pressure decreases volume increases

Charles’s Law

At a constant pressure, as temperature increases, volume increases. As temperature decreases, volume decreases

Gay Lussac’s Law

At a constant volume, as temperature increases, pressure increases. As temperature decreases, pressure decreases.

Diffusion

the mixing of gases from areas of high concentration to areas of low concentration

Effusion

the process whereby the molecules of a gas confined in a container randomly pass through a tiny opening in the container

Graham’s Law of Effusion

the rates of effusion of gases at the same temperature and pressure are inversely proportional to the square roots of their molar masses

Colloid

mixed particles remain suspended in the mixture

Suspension

mixed particles will settle to the bottom without constant agitation or stirring

Solvent

substance that dissolves the solute

Solute

substance that is dissolved in or by the solvent

Soluble

capable of being dissolved

Tyndall Effect

Light passes through a solution but is scattered in a colloid or a suspension

Electrolyte

a substance that dissolves in water to give a solution that conducts electrical current

Non-Electrolyte

a substance that dissolves in water to give a solution that does not conduct an electrical current (contains no ions in solution)

Dissociation

separation of ions that occurs when an ionic compound dissolves in water. The water simply separates the positively and negatively charged particles and surrounding them through solvation

Dilution

creating less concentrated solutions

Saturated

maximum amount of dissolved solute for given amount of solvent at a given temperature

Unsaturated

less than the maximum amount of dissolved solute for given amount of solvent at a given temperature

Supersaturated

more solute dissolved than can theoretically be dissolved

Arrhenius Acids

Increases the concentration of H+ ions

Arrhenius Bases

increase the concentration of OH- ions

Bronsted-Lowry Acid

Proton (H+) donor

Bronsted-Lowry Base

Proton (H+) acceptor