Regents Chemistry Units 1-12

Substance

form of matter with constant chemical composition and properties

Mixture

two substances that were mixed physically (not chemically bonded)

Compound

two substances that were chemically combined

Homogeneous mixture

mixture components are evenly distributed

Heterogenous mixture

mixture where the components are not evenly distributed and are easily distinguishable

Solutions are always _____

Homogenous

Kelvin to celcius

Celcius = Kelvin - 273

Charge of an atom’s nucleus

positive

Electron’s charge

negative

Orbitals

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

Where are protons and neutrons found?

in the nucleus

Charge of protons

positive

Charge of neutrons

0 (no charge/neutral)

The number of protons in an atom equals:

the number of electrons

Mass of a proton

1 amu

Mass of a neutron

1 amu

Mass of electron

~0 amu

Atomic mass

number of protons + number of neutrons

Ground state

when all electrons are at their lowest possible energy (as shown in reference table)

Bright line spectrum

formed when a electron returns from a higher energy state to a lower energy state

Valence electrons

electrons in the outermost shell

Atomic number

number of protons in an element

Isotpoes

atoms with the same atomic number (protons only) but different atomic masses (protons + neutrons)

Average atomic mass of an element

weighted average of its naturally occurring isotopes

Ratio of protons to neutrons in a stable isotope

1:1

If an element has an atomic number higher than 83, it is _____

radioactive

Transmutation

change in the nucleus of an atom so it changes to a new type of atom (new element)

Artificial transmutation

transmutation that occurs by a bombardment of the nucleus by high energy particles

Nuclear fission

the nucleus of an atom is split by shooting the nucleus with a neutron

Nuclear fusion

combines 2 light nuclei to form a heavier nuclei

Is energy released from nuclear reactions greater or less than energy released from chemical reactions?

greater

How are chemical compounds formed?

atoms are bonded together

Breaking a chemical bond ______ energy

absorbs (endothermic)

Forming a chemical bond ______ energy

releases (exothermic)

Ionic bond

bond formed when valence electrons are transferred from one atom to another

Covalent bond

bond formed when valence electrons are shared between atoms

Metallic bond

bond formed when valence electrons are mobile in free moving ‘sea’ of electrons

Properties of ionic substances

high melting and boiling points, form crystals, dissolve in water, conduct electricity

Properties of covalent substances

low melting and boiling points, do not conduct electricity

Polar bond

covalent bond where electrons are shared unevenly

Are polar molecules symmetrical or asymmetrical

asymmetrical

Are nonpolar molecules symmetrical or asymmetrical

asymmetrical

When an atom gains an electron, it becomes a ______ ion

negative

When an atom loses an electron, it becomes a ______ ion

positive

Electronegativity

how strongly an atom attracts electrons in a chemical bond

0.0-0.4 electronegativity

non-polar covalent

0.4-1.7 electronegativity

polar covalent

1.7+ electronegativity

ionic

Metals react with nonmetals to form ____ compounds

ionic

Nonmetals bond with nonmetals to form ____ compounds

covalent

Mixture

composed of two or more different substances that can be physically separated

Compound

two or more elements bonded together

Heat of fusion

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

Heat of vaporization

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

Specific heat

energy required to raise one gram of a substance 1 degree (C or K)

Increase in pressure

decrease in volume

Increase in temperature

increase in volume

Increase in temperature

increase in pressure

A real gas is most like an ideal gas when it is at ________________

low temperature and high pressure

Potential energy

stored energy

Kinetic energy

energy of motion

Heat transfers from ____

high to low

Temperature

a measure of average kinetic energy of particles in a sample

Is temperature a form of energy?

no

Exothermic

gives off energy

Endothermic

absorbs energy

Elements are arranged in order of _____

increasing atomic number

Atomic mass

sum of protons and neutrons in nucleus

Isotopes of an element have _____

the same number of protons but different number of neutrons

As you progress down a group

atomic radius increases

electronegativity decreases

first ionization energy decreases

metallic character increases

As you progress left to right across a row

atomic radius decreases

electronegativity increases

first ionization energy increases

metallic character decreases

Empirical formula

formula with the simplest whole number ratios

Molecular formula

shows actual number of atoms per element in a single molecule

Structural formula

shows number of each type of atom as well as their physical arrangement

Formula mass of a substance

sum of the atomic masses of its atoms

Molar mass (gram formula mass)

the mass of one mole of that substance

Solution

solute dissolved in a solvent

Ionic substances dissolve in _____ solvents

polar

Adding solute to a solvent causes boiling point of solvent to ____ and freezing point to ____

increase, decrease

Saturated solution is in _____

equilibrium

Collision theory

reaction is most likely to occur if particles collide with proper energy and orientation

At equilibrium, the rate of forward reactions and reverse reactions are ____

the same

Heat of reaction

PE of the products - PE of the reactants

Positive heat of reaction

endothermic

Negative heat of reaction

exothermic

Catalyst

lowers activation energy

Entropy

measure of randomness or disorder in a system

Systems in nature tend towards lower ____ and higher ___

energy, entropy

Exothermic reactions that result in increased entropy are ______

spontaneous

Arrhenius acids and bases are _____

electrolytes

Electrolyte

substance that forms a solution capable of conducting electricity when dissolved in water

Acids yield __ ions

H+

Bases yield __ ions

OH-

Neutralization reaction

acids and bases react to form salt and water

Titration

process where volume of a solution of known concentration is used to determine concentration of another solution

Acid is a __

H+ donor

Base is a __

H+ acceptor

High concentration of H+ ions =

low pH

Low concentration of H+ ions =

high pH

On the pH scale, each decrease of one pH unit = a ____ increase in H+ ion concentration

tenfold