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Chemistry Regents

Key Concepts:

Terms in this set (175)

True or False: The modern model of the atom has evolved over a long period of time through the work of many scientists.
True
Characteristics of Dalton's Model (3)
Elements are made of atoms
Atoms of an element are the same.
Compounds are formed from combinations of atoms.
Characteristics of Rutherford Experiment (1)
Bombarded gold foil with alpha particles. Showed atoms
were mostly empty space with small, dense positively
charged nucleus.
Characteristics of the Bohr model (1)
Small, dense, positively charged nucleus surrounded by electrons in circular
orbits.
Characteristics of the Wave-Mechanical Model (Modern Atomic Theory) (2)
Small, dense, nucleus positively charged nucleus
surrounded by electrons moving in "electron cloud".
"Orbitals" are areas where an electron with a certain amount of energy is most
likely to be found.
Where are Protons and Neutrons located?
Protons and neutrons are found in the nucleus.
The number of protons in an atom equals
the number of electrons.
The positive charges of the protons are cancelled by the negative charges of the electrons, so overall an atom has a neutral charge.
Masses of subatomic particles:
The mass of a proton is 1 amu. The mass of a neutron is 1 amu. The mass of an electron is almost 0 amu.
The amu is defined as 1/12 the mass of a Carbon atom.
The atomic mass of an atom is equal to the total number of protons
and neutrons.
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.
How is a bright line spectrum produced?
An electron returns from a higher energy state to a lower energy state, it emits a specific amount of energy usually in the form of light.
Instrument used to see the bright line spectrum
The instrument used to see the bright line spectrum is called a spectroscope.
Valence Electrons
Electrons in the outermost shell. These affect the chemical properties of the element.
Atoms with a filled valence level are stable.
Most elements can have up to 8 electrons in their valence level. The exceptions are H
and He, which can have only 2 valence electrons.
Atoms form bonds in order to fill their valence levels.
You can use orbital notation or Lewis structures to show the configuration of the
valence electrons.
Atoms of the same element all contain the same number of:
Protons.
Changing the number of protons changes the atom into a different element. The atomic number is the number of protons in an atom of an element.
What are Isotopes?
Isotopes are atoms with equal numbers of protons but different numbers of neutrons.
Isotopes of an element have the same atomic number (protons only), but different
atomic masses (protons + neutrons).
What is the average atomic mass of an element?
The average atomic mass of an element is the weighted average of its naturally occurring isotopes.
What does the stability of an isotope depend on?
The stability of an isotope depends on the ratio of protons to neutrons in the nucleus.
Most nuclei are stable, but some are unstable. These nuclei will spontaneously decay,
emitting radiation.
Stable isotopes have a 1:1 ratio of protons and neutrons. Most radioactive isotopes
have twice as many neutrons as protons.
All elements with an atomic number higher than 83 are radioactive.
Transmutation
A change in the nucleus of an atom changes it to a new type of atom (i.e. a new element). This is called transmutation.
Transmutation can occur naturally or artificially.
Artificial transmutation requires the bombardment of a nucleus by high energy
particles.
Spontaneous Decay
Spontaneous decay can involve the release of different particles from the nucleus.
The types of particles, as well as their masses and charges, can be found on Table O.
Nuclear Fission
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
Nuclear fusion combines two light nuclei to form heavier nuclei. Nuclear fusion is the
process that powers the sun.
Nuclear fusion requires very high temperatures, and is not yet ready for practical use.
The main advantage it offers is that the products are not radioactive wastes (as with fission).
Nuclear Reaction v. Chemical Reaction
The energy released from nuclear reactions is much greater than that released from chemical reactions.
The risks associated with using radioactive isotopes include:
Biological exposure (which may cause radiation poisoning and cancer), long-term storage and disposal, and nuclear accidents.
Radioactive isotopes may be used in:
Medicine (tracing chemical and biological processes), radioactive dating, industrial measurement, nuclear power, and detection and treatment of disease.
Chemical compounds are formed when:
Atoms are bonded together.
Breaking of chemical bonds is an:
Endothermic process.
Formation of chemical bonds is an:
Exothermic process.
Comppounds vs. Individual atoms:
Compounds have less potential energy than the individual atoms they are formed
from.
Two major categories of compounds are:
ionic and molecular (covalent) compounds.
Compounds can be differentiated by their chemical and physical properties (Ionic, Covalent, Polar).
Ionic substances have high melting and boiling points, form crystals, dissolve in water (dissociation), and conduct electricity in solution and as a liquid.
Covalent or molecular substances have lower melting and boiling points, do not conduct electricity.
Polar substances are dissolved only by another polar substance. Non-polar substances are dissolved only by other non-polar substances.
Ionic bonds are formed when:
Transferred from one atom to another - ionic.
Covalent bonds are formed when:
Shared between atoms - covalent.
Metallic bonds are formed when:
Mobile in a free moving "sea" of electrons - metallic.
Polarity of a molecule can be determined by:
Its shape and the distribution of the charge.
Polar molecules must have polar bonds.
Polar molecules are asymmetrical.
Nonpolar molecules are symmetrical and/or have no polar bonds.
When an atom gains an electron:
it becomes a negative ion and its radius
increases.
When an atom loses an electron:
it becomes a positive ion and its radius decreases.
Atoms gain a stable electron configuration by:
Bonding with other atoms.
Atoms are stable when they have a full valence level.
Most atoms need 8 electrons to fill their valence level.
H and He only need 2 electrons to fill their valence level.
The noble gasses (group 18) have filled valence levels. They do not normally bond
with other atoms.
Characteristics of theElectron-dot diagrams (Lewis structures):
represent the valence electron arrangement in elements, compounds and ions.
Electrons in Lewis structures are arranged by their orbitals.
The first two electrons are placed together in the "s" orbital.
The remaining electrons are spread among the 3 "p" orbitals.
The "s" orbital must be filled first. Then each "p" orbital must have one electron
before another "p" orbital gains a second.
Electronegativity
indicates how strongly an atom of an element attracts electrons in a chemical bond. These values are based on an arbitrary scale.
The electronegativity difference between two bonded atoms can determine the type of bond and its polarity.
0.0 - 0.4 = non-polar covalent
0.4-1.7 = polar covalent
1.7+ = ionic
Bonding guidelines:
Metals react with nonmetals to form ionic compounds.
Nonmetals bond with nonmetals to form covalent compounds (molecules).
Ionic compounds with polyatomic ions have both ionic and covalent bonds.
Intermolecular Forces
Allow different particles to be attracted to each other to form solids and liquids.
Hydrogen bonds are an example of a strong IMF between atoms.
Hydrogen bonds exist between atoms of hydrogen and oxygen, fluorine, or nitrogen.
Substances with hydrogen bonds tend to have much higher melting and boiling points
than those without hydrogen bonds.
Physical properties of a substance can be explained in terms of chemical bonds and intermolecular forces.
These include conductivity, malleability, solubility, ductility, hardness, melting point and boiling point.
True or False: Matter is classified as a pure substance or a mixture of substances.
True, Matter is classified as a pure substance or a mixture of substances.
A substance has fixed composition and uniform properties throughout the sample.
Element and compounds are substances.
A mixture is composed of:
two or more different substances that may be physically separated.
Characteristics of mixtures (4):
A mixture may be homogeneous (uniform - a solution), or heterogeneous (uneven).
Substances in a mixture retain their original properties.
Substances in a mixture may be separated by their size, polarity, density, boiling and freezing points, and solubility (among others).
Filtration and distillation are examples of processes used to separate mixtures.
An element is a substance composed of:
atoms with the same atomic number. They cannot be broken down by chemical change.
A compound is two or more elements bonded together. It can only be broken down by:
Chemical Changes.
Substances that form a compound gain new properties.
The ratio of substances in a compound is constant (e.g. water has a fixed ratio 2:1
ratio of hydrogen to oxygen).
A physical change is one that results in:
The rearrangement of existing particles in a substance (ex: freezing, boiling). A chemical change results in the formation of different substances with different properties.
Chemical and physical changes may be endothermic or exothermic.
The three phases of matter are:
solid, liquid and gas. Each has its own properties.
Solids have a constant volume and shape. Particles are held in a rigid, crystalline structure.
Liquids have a constant volume but a changing shape. Particles are mobile but still held together by strong attraction.
Gasses have no set volume or shape. They will completely fill any closed contained. Particles have largely broken free of the forces holding them together.
A 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).
When the substance undergoes a phase change, there is no change in temperature.
The line "flattens" until the phase change is complete.
When a phase change is occurring, the potential energy of the substance changes
while kinetic energy remains the same.
As temperature increases, kinetic energy increases.
Heat of fusion (Hf):
Is the energy needed to convert one gram of a substance from solid to liquid.
Heat of vaporization (Hv):
Is the energy needed to convert one gram of a substance from liquid to gas.
Specific heat (C):
Is the energy required to raise one gram of a substance 1 degree (Celcius or Kelvin).
The specific heat of liquid water is 1 cal/gJ or 4.2 J/gK.
The combined gas law:
States the relationship between pressure, temperature and volume in a sample of gas.
Increasing pressure causes a decrease in volume (inverse relationship).
Increasing temperature causes an increase in volume (direct relationship).
Increasing temperature causes an increase in pressure.(direct relationship).
An ideal gas model is used to:
Explain the behavior of gasses. A real gas is most like an ideal gas when it is at low temperature and high pressure.
The Kinetic Molecular Theory (KMT) for an ideal gas states that 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.
Equal volumes of gasses at the same temp and pressure have an:
Equal number of particles.
Energy can exist in different forms :
chemical, electrical, electromagnetic, thermal, mechanical, nuclear.
Potential Energy
Stored energy.
Kinetic Energy
Energy of motion.
The Law of Conservation of Energy
states that energy can not be lost or destroyed, only changed from one form to another.
Heat
Heat is a transfer of energy (often but not always thermal energy) from a body of higher temperature to a body of lower temperature.
Temperature
Temperature is a measure of the average kinetic energy of the particles in a sample. Temperature is NOT a form of energy and should not be confused with heat.
The concepts of kinetic and potential energy can be used to explain physical processes such as:
Fusion (melting), solidification (freezing), vaporization (boiling, evaporation), condensation, sublimation, and deposition.
Processes that are exothermic:
Give off heat energy. This typically causes the surrounding environment to become warmer.
Processes that are endothermic:
Absorb energy. This typically causes the surrounding environment to become colder.
True or False: The placement of an element on the Periodic Table does not give an indication of the chemical and physical properties of that element.
False. The placement of an element on the Periodic Table gives an indication of the chemical and physical properties of that element.
Elements are arranged in order of:
Increasing atomic number.
The number of protons in an atom only changes through:
Nuclear Reactions.
The atomic mass is the sum of:
Protons and neutrons in the nucleus.
The mass number given on the periodic table is a weighted average of the different isotopes of that element.
Electrons do not significantly add to the atomic mass.
Elements can be classified by their properties and their location on the Periodic
Table as:
Metals, non-metals, metalloids, and noble gasses.
Elements may be differentiated by their physical properties like (6):
Density, conductivity, malleability, hardness, ductility, solubility.
Elements of the same period have the same number of:
Occupied energy levels.
Elements of the same group have the same:
Valence configuration and similar chemical properties.
Specific groups and characteristics:
Group 1 elements other than H are alkali metals.
Group 2 elements are alkali earth metals.
Group 17 elements are halogens.
Alkali metals, alkali earth metals, and halogens all are highly reactive and do not exist
as free elements in nature (they are all found in compounds).
Group 18 elements are noble or inert gasses. These elements have filled valence
levels and are do not normally react with other substances.
As you progress down a group:
atomic radius increases.
electronegativity decreases.
first ionization energy decreases.
metallic character increases.
As you progress across a group from left to right:
atomic radius decreases.
electronegativity increases.
first ionization energy increases.
metallic character decreases.
Why do some elements may exist in two or more forms in the same phase?
These forms differ in their molecular or crystal structure, hence their different properties.
Ex: Carbon exists as both graphite and diamond (a network solid).
Compound
Is a substance composed of two or more different elements that are chemically combined in a fixed proportion. A chemical compound can only be broken down by chemical means.
Types of chemical formulas include:
Empirical, molecular, and structural.
Empirical formulas show 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.
All chemical reactions show a:
Conservation of mass, energy and charge.
A balanced chemical equation represents:
Conservation of atoms.
The coefficients in a balanced chemical equation can be used to determine:
Mole ratios in the reaction.
The formula mass
The sum of the atomic masses of its atoms. The molar mass (gram formula mass) equals the mass of one mole of that substance.
Percent Composition
The percent composition by mass of each element in a compound can be calculated mathematically.
Types of chemical reactions include:
Synthesis, decomposition single replacement, and double replacement.
Solution
Is a homogeneous mixture of a solute dissolved in a solvent.
Solubility
Solubility depends on temperature, pressure, and the nature of the solute and solvent.
"Like dissolves like" - polar substances dissolve polar substances, and non-polar
substances dissolve non-polar substances. Polar and non-polar do not mix.
10
Ionic substances dissolve in:
Polar solvents. The positive ion is attracted to the negative end of the polar molecule, as the negative ion is attracted to its positive end.
Concentration of a solution can be expressed as:
Molarity (M), percent by volume, percent by mass, or parts per million (ppm).
Adding a solute to a solvent causes:
The boiling point of the solvent to increase and the freezing point to decrease.
A saturated solution exists in:
equilibrium - the rate of crystallization equals the rate of dissolving.
Collision theory
States that a reaction is most likely to occur if reactant particles collide with the proper energy and orientation.
The rate of a chemical reaction depends on several factors:
Temperature, concentration, nature of the reactants, surface area and the presence of a catalyst.
True or False: Some chemical and physical changes can reach equilibrium.
True, Some chemical and physical changes can reach equilibrium.
At equilibrium the rate of the forward reaction equals:
The rate of the reverse reaction.
The measurable quantities of reactants and products remain:
Constant at equilibrium.
LeChatelier's principle can be used to predict:
The effect of stress on a system in equilibrium.
Stresses include a change in pressure, volume, concentration, and temperature.
Energy absorbed or released by a chemical reaction can be represented by a:
Potential energy diagram.
Heat of Reaction
The amount of energy released or absorbed during a chemical reaction is the heat of reaction.
Positive heat of reaction
Endothermic reaction.
Negative heat of reaction
Exothermic reaction.
Catalyst
Provides an alternative pathway for a chemical reaction. The catalyzed reaction requires a lower activation energy than the uncatalyzed reaction.
Adding a catalyst increases the rate of the forward and reverse reactions equally, so
there is no shift in equilibrium.
Entropy
is a measure of the randomness or disorder in a system. A system with greater disorder has greater entropy.
Systems in nature tend to undergo changes towards:
Lower energy and higher entropy.
Exothermic reactions that result in increased entropy:
Are spontaneous.
Arrhenius theory
Behavior of many acids and bases can be explained by the Arrhenius theory. Arrhenius acids and bases are electrolytes.
There are other acid-base theories besides the Arrhenius theory. One states that an acid is an H+ donor and a base an H+ acceptor.
Electrolyte
An electrolyte is 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 yield ____ ions as the only positive ion in solution.
Arrhenius acids yield H+(aq) ions as the only positive ion in solution.
H+(aq) ions may also be written as H3O+(aq) ions (hydronium ions).
Arrhenius bases yield ____ ions as the only negative ion in solution.
Arrhenius bases yield OH-(aq) ions as the only negative ion in solution.
Organic compounds with OH- are not bases.
Ammonia (NH3) is a base.
Neutralization Reactions
In neutralization reactions an Arrhenius acid and an Arrhenius base react to form salt and water.
The net ionic equation for all neutralization reactions is the same: H+(aq) + OH- (aq)
H2O (l)
Titration
Titration is a lab process in which a volume of a solution of known concentration is used to determine the concentration of another solution. Titration is a practical application of a neutralization reaction.
The acidity or alkalinity of a solution can be measured by:
pH.
A low pH indicates a higher concentration of H+ ions than OH- ions.
A high pH indicates a lower concentration of H+ ions than OH- ions.
A neutral pH (7) indicates an equal concentration of H+ ions than OH- ions. Pure water has a neutral pH.
On the pH scale, each decrease of one pH unit represents a:
Tenfold increase in H+ ion concentration.
An oxidation-reduction (redox) reaction involves:
The transfer of electrons (e-).
Reduction
Reduction is the gain of electrons and decrease of oxidation number.
A half reaction can be written to represent reduction.
Oxidation
Oxidation is the loss of electrons and increase of oxidation number.
A half reaction can be written to represent oxidation.
In redox the number of electrons lost is equal to:
The number of electrons gained.
Changes in oxidation numbers indicate:
That a redox reaction has occurred.
Double replacement reactions are not redox reactions.
A reaction in which an element is alone on one side of a reaction, and part of a
compound on the other side is always a redox reaction.
Electrochemical cells
In an electrochemical cell oxidation occurs at the anode and reduction at the cathode.
Voltaic cells
A voltaic cell spontaneously converts chemical energy to electrical energy.
Electrolysis
An electrolytic cell requires energy to produce a chemical change. This is called electrolysis.
Organic compounds consist of carbon atoms which:
Bond to each other in chains, rings and networks to form a variety of structures.
Hydrocarbons
Hydrocarbons are compounds that contain only carbon and hydrogen.
Saturated hydrocarbons
Saturated hydrocarbons contain only single carbon-carbon bonds.
Unsaturated hydrocarbons
Unsaturated hydrocarbons contain at least one multiple carbon-carbon bond (double
or triple bond).
categories of organic molecules
Organic acids, alcohols, esters, aldehydes, ketones, ethers, halides, amines, amides, and amino acids- all differ in their structures.
Functional groups
Functional groups give organic molecules distinct physical and chemical properties.
Isomers of organic compounds have the same:
Molecular formula but different structures and properties.
Multiple Covalent bond
In a multiple covalent bond, more than one pair of electrons are shared between two atoms.
Unsaturated Organic Compounds
Unsaturated organic compounds contain at least one double or triple bond.
Types of organic reactions include:
Addition, substitution, polymerization, esterification, fermentation, saponification, and combustion.
Any standard chemistry lab procedure is fair game for the Regents. Specific skills that may be tested include:
Using the scientific method for a controlled experiment. Construct a graph.
Use proper units of measurement.
Making accurate and precise measurements.
Use rules for significant figures.
Identification and use of lab equipment.
Lab safety.
Cations
Positive (+) ions and form when a neutral atom loses electrons. They are smaller than their parent atom.
Anions
Negative (-) ions and form when a neutral atom gains electrons. They are larger than their parent atom.
J.J. Thompson
Discovered the electron snd developed the "Plum-Pudding" model of the atom. --> Positive and Negative particles spread throughout entire atom.
Diatomic Molecules
Elements that form two atom molecules in their natural form at STP. BrINClHOF (Br2, I2, N2, Cl2, H2, O2, F2).
Volume of Gas
22.4 (L)
Avogardo's number
6.02 x (10^23) = Number of particles
Physical Changes
Do not form new substances. Merely change the appearance of the original material.
Chemical Changes
Results in formation of new substances.
Synthesis reactions
occur when two or more reactants combine to form a single product.
Decomposition reactions
Occurs when a single reactant forms two or more products.
Single replacement reactions
Occur when one element replaces another element in a compound.
Double replacement reactions
Occur when two compounds react to form two new compounds.
Sublimation
substances that turn from a solid directly into a gas (CO2 and I2)
Distillation
Separates mixtures with different boiling points.
Filtration
Separates mixtures of solids and liquids.
Chromatography
Can be used to separate mixtures of liquids and mixtures of gases.
Location of metals, nonmetals, metalloids:
Found left of the "staircase", nonmetals are above it, and metalloids border it.
Characteristics of metals:
Malleable, Ductile, Lustrous, Good conductors, Low ionization energy, low electronegativity, tends to form ions.
Characteristics of nonmetals:
Brittle when solid, Mostly gases at STP, dull, good insulators, high ionization energy, high electronegativity, tend to form ions.
Noble Gases
Stable due to having a full shell of valence electrons.
Covalent bonds
Two atoms share an electron
Ionic bonds
one atom transfers an electron to another atom when forming a bond with itself.
Nonpolar covalent bonds
Form when two atoms of the same element bond together.
Hydrogen Bonds
Hydrogen bonds to the elements N, O, or F and gives the compound unusually high melting and boiling points.
Solubility and Temperature
As temperature increases, solubility increases.
Temperature and Reaction rate
As temperature increases, the reaction rate increases.
Exothermic or Endothermic
Enthalpy (H)
The heat energy gained or lost in a reaction.
Adding a reactant to a system:
Shifts equilibrium away from added substance.
Removing a reactant in a system:
Shifts equilibrium towards a substance.
Increase in temperature in a system:
Shifts equilibrium in the endothermic direction.
Decrease in temperature in a system:
Shifts equilibrium in the exothermic direction.
Increasing the pressure in a system:
Shifts equilibrium in the direction of the side with fewer moles.
Decreasing the pressure in a system:
Shifts equilibrium in the direction of the side with more moles.
Combustion reactions
Occur when a hydrocarbon reacts with oxygen to make CO2 and H2O.
Organic substitution reactions
When an Alkane and a Halogen react so that one or more hydrogen atoms on the Alkane are replaced with oxygen.
Esterification
Occurs when an organic acid and an alcohol react to make water and an ester.
Saponification
Occurs when an ester reacts with a base to make alcohol and soap.
Fermentation
Reactions occur when yeast catalyze a sugar to make carbon dioxide and ethanol.
Alpha Particles
Positively charged.
Beta Particles
Negatively charged.
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