Chemistry Regents Exam Vocabulary

Flashcards for Chemistry Regents Exam Review: Vocabulary Style

Dalton’s Model

Elements are made of atoms, Atoms of an element are the same, Compounds are formed from combinations of atoms

Rutherford Experiment

Bombarded gold foil with alpha particles, Showed atoms were mostly empty space with small, dense positively charged nucleus.

Bohr Model

Small, dense, positively charged nucleus surrounded by electrons in circular orbits.

Wave-Mechanical Model (Modern Atomic Theory)

Small, dense, nucleus positively charged nucleus surrounded by electrons moving in “electron cloud”.

Orbitals

Areas where an electron with a certain amount of energy is most likely to be found.

Atom Charge

The positive charges of the protons are cancelled by the negative charges of the electrons, so overall an atom has a neutral charge.

amu

Defined as 1/12 the mass of a Carbon atom.

Ground State

When all electrons are at their lowest possible energy.

Excited State

When the electron gains a specific amount of energy, it moves to a higher orbital.

Spectroscope

The instrument used to see the bright line spectrum.

Valence Electrons

The outermost electrons that affect the chemical properties of the element.

Stable Atoms

Atoms with a filled valence level.

Atomic Number

The number of protons in an atom of an element.

Isotopes

Atoms with equal numbers of protons but different numbers of neutrons.

Average Atomic Mass

The weighted average of its naturally occurring isotopes.

Unstable Nuclei

Nuclei that spontaneously decay, emitting radiation.

Half-Life

The rate of decay, a constant that can never be changed.

Transmutation

A change in the nucleus of an atom changes it to a new type of atom.

Artificial Transmutation

Requires the bombardment of a nucleus by high energy particles.

Nuclear Fission

Occurs when the nucleus of an atom is split. This can be caused artificially by “shooting” the nucleus with a neutron.

Nuclear Fusion

Combines two light nuclei to form heavier nuclei.

Endothermic Process

Breaking a chemical bond.

Exothermic Process

Forming a chemical bond

Ionic Substances Properties

High melting and boiling points, form crystals, dissolve in water (dissociation), and conduct electricity in solution and as a liquid.

Covalent/Molecular Substances Properties

Lower melting and boiling points, do not conduct electricity.

Ionic Bond

Transferred from one atom to another.

Covalent Bond

Shared between atoms

Metallic Bond

Mobile in a free moving “sea” of electrons

Electronegativity

How strongly an atom of an element attracts electrons in a chemical bond.

Hydrogen Bonds

An example of a strong IMF between atoms. Exists between atoms of hydrogen and oxygen, fluorine, or nitrogen. Substances with these bonds tend to have much higher melting and boiling points than those without.

Substance

Has fixed composition and uniform properties throughout the sample. Element and compounds are substances.

Mixture

Composed of two or more different substances that may be physically separated. May be homogeneous (uniform – a solution), or heterogeneous (uneven).

Physical Change

The rearrangement of existing particles in a substance (ex: freezing, boiling).

Chemical Change

Results in the formation of different substances with different properties.

Heating Curve (or cooling curve)

Traces the changes in temperature of a substance as it changes from solid to liquid to gas (or gas to liquid to solid).

Heat of Fusion (Hf)

The energy needed to convert one gram of a substance from solid to liquid.

Heat of Vaporization (Hv)

The energy needed to convert one gram of a substance from liquid to gas.

Specific Heat (C)

The energy required to raise one gram of a substance 1 degree (Celcius or Kelvin).

Kinetic Molecular Theory (KMT)

All gas particles are in random motion, have no forces of attraction between them, have a negligible volume compared to the distances between them & have collisions that result in the transfer of energy from one particle to another, but there is no net loss of energy from the collision.

Potential Energy

Stored energy.

Kinetic Energy

Energy of motion.

Heat

A transfer of energy (often but not always thermal energy) from a body of higher temperature to a body of lower temperature.

Temperature

A measure of the average kinetic energy of the particles in a sample.

Exothermic Processes

Give off heat energy. This typically causes the surrounding environment to become warmer.

Endothermic Processes

Absorb energy. This typically causes the surrounding environment to become colder.

Atomic Mass

The sum of protons and neutrons in the nucleus.

Empirical Formula

Shows elements in their simplest whole number ratios. This may or may not be the same as the molecular formula.

Molecular Formulas

Show the actual number of atoms per element in a single molecule.

Structural Formulas

Show the number of each type of atom as well as their physical arrangement.

Solution

A homogeneous mixture of a solute dissolved in a solvent.

Collision Theory

States that a reaction is most likely to occur if reactant particles collide with the proper energy and orientation.

Catalyst

A alternative pathway for a chemical reaction. The catalyzed reaction requires a lower activation energy than the uncatalyzed reaction.

Entropy

A measure of the randomness or disorder in a system.

Electrolyte

A substance which, when dissolved in water, forms a solution capable of conducting electricity. The ability to conduct electricity depends on the concentration of ions.

Arrhenius Acids

H+(aq) ions as the only positive ion in solution.

Arrhenius Bases

OH-(aq) ions as the only negative ion in solution.

Titration

A lab process in which a volume of a solution of known concentration is used to determine the concentration of another solution. A practical application of a neutralization reaction.

Oxidation-Reduction (Redox) Reaction

Involves the transfer of electrons (e-).

Reduction

The gain of electrons and decrease of oxidation number.

Oxidation

The loss of electrons and increase of oxidation number.

Voltaic Cell

Spontaneously converts chemical energy to electrical energy.

Electrolytic Cell

Requires energy to produce a chemical change. This is called electrolysis.

Hydrocarbons

Compounds that contain only carbon and hydrogen.

Saturated Hydrocarbons

Contain only single carbon-carbon bonds.

Unsaturated Hydrocarbons

Contain at least one multiple carbon-carbon bond (double or triple bond).

Functional Groups

Give organic molecules distinct physical and chemical properties.