A substance that has the same composition and properties wherever it is found
Chemistry
The study of the composition, structure, properties, and reactions of matter
Conclusion
An explanation of an observation that has been validated by repeated experiments that support a hypothesis
Experiment
A procedure that tests the validity of a hypothesis
Hypothesis
An unverified explanation of a natural phenomenon
Observation
Information determined by noting and recording a natural phenomenon
Scientific Method
The process of making observations, proposing a hypothesis, testing the hypothesis, and making a conclusion as to the validity of the hypothesis
Scientific Notation
A form of writing large and small numbers using a coefficient that is at least 1 but less than 10, followed by a power of 10
Celcius Temperature Scale
A temperature scale on which water has a freezing point of 0 C and a boiling point of 100 C
Centimeter (cm)
A unit of length in the metric system; there are 2.54 cm in 1 in
Conversion Factor
A ratio in which the numerator and denominator are qualities from an equality or given relationship. For example, the conversion factors for one metric conversion:
Cubic centimeter (cc or cm^3)
The volume of a cube that has 1-cm sides.
Density
The relationship of the mass of an object to its volume expressed as grams per cubic meter (g/cm^3), grams per milliliter (g/mL), or grams per liter (g/L)
Equality
A relationship between two units that measure the same quantity
Exact Number
A number obtained by counting or by definition
Gram (g)
The metric unit used in measurements of mass
International System of Units
An international system of units that modifies the metric system
Kelvin (K) Temperature Scale
A temperature scale on which the lowest possible temperature is 0 K
Kilogram (Kg)
The SI unit of mass. There are 1,000 grams in a kilogram
Liter (L)
The metric unit for volume that is slightly larger than a quart
Mass
A measure of the quantity of material in an object
Measured Number
A number obtained when a quantity is determined by using a measuring device
Meter (m)
The metric unit for length that is slightly longer than a yard. The meter is the SI standard unit of length.
Metric System
A system of measurement used by scientists and in most countries
Milliter (mL)
A metric unit of volume equal to one-thousandth of a liter (0.001 L)
Prefix
The part of the name of a metric unit that precedes the base unit and specifies the size of the measurement. All prefixes are related on a decimal scale.
Second (s)
A unit of time used in both the SI and metric systems
Significant Figures (SFs)
The numbers recorded in a measurement
Specific gravity (sp gr)
A relationship between the density of a substance and the density of water.
Temperature
An indicator of the hotness or coldness of an object
Volume
The amount of space occupied by a substance
Boiling
The formation of bubbles of gas throughout a liquid
Boiling Point (bp)
The temperature at which a liquid changes to gas (boils) and gas changes to liquid (condenses)
Calorie (cal)
The amount of heat energy that raises the temperature of exactly 1g of water by exactly 1 C
Change of State
The transformation of one state of matter to another for example, solid to liquid, liquid to solid, liquid to gas
Chemical Change
A change during which the original substance is connected into a new substance that has a different composition and new physical and chemical properties
Chemical Properties
The properties that indicate the ability of a substance to change into a new substance
Compound
A pure substance consisting of two or more elements with a definite composition, that can be broken down into simpler substances only by chemical methods
Condensation
The change of state from a gas to a liquid
Cooling Curve
A diagram that illustrates temperature changes and changes of state for a substance as heat is removed
Deposition
The change of a gas directly into a solid; the reverse of sublimation
Element
A pure substance containing only one type of matter, which cannot be broken down by chemical methods
Energy
The ability to do work
Energy Value
The kilocalories (or kilojoules) obtained per gram of the food types: carbohydrates, fat, and protein
Evaporation
The formation of a gas (vapor) by the escape of high-energy molecules from the surface of a liquid
Freezing
The change of state from a liquid to solid
Freezing Point (fp)
The temperature at which a liquid changes to a solid (freezes), a solid changes to a liquid (melts)
Gas
A state of matter that does not have a definite shape or volume
Heat
The energy associated with the motion of particles in a substance
Heat of Fusion
The energy required to melt exactly 1 g of a substance at its melting point. For water, 80. cal (334 J) is needed to melt 1 g of ice; 80. ca (334 J) is released when 1 g of water freezes
Heat of Vaporization
The energy required to vaporize exactly 1 g go a substance at its boiling point. For water, 540 cal (2260 J) is needed to vaporize 1 g of liquid; 1 g of steam gives off 540 cal (2260 J) when it condenses
Heating Curve
A diagram that illustrates the temperature changes and changes of state of a substance as it is heated
Joule (J)
The SI unit of heat energy; 4.184 J = 1 cal
Kinetic Energy
The energy of moving particles
Liquid
A state of matter that takes the shape of its container but has a definite volume
Matter
The material that makes up a substance and has mass and occupies space
Melting
The change of state from a solid to a liquid
Melting Point (mp)
The temperature at which a solid becomes a liquid (melts). It is the same temperature as the freezing point.
Mixture
The physical combination of two or more substances that does not change the identities of the mixed substances
Physical Change
A change in which the physical properties of a substance change but its identity stays the same
Physical Properties
The properties that can be observed or measured without affecting the identity of a substance
Potential Energy
A type of energy related to position or composition of a substance
Pure Substance
A type of matter that has a definite composition
Solid
A state of matter that has its own shape and volume
Specific Heat (SH)
A quantity of heat that changes the temperature of exactly 1 g of a substance by exactly 1 C
States of Matter
Three forms of matter: solid, liquid, and gas
Sublimation
The change of state in which a solid is transformed directly to a gas without forming a liquid first
Alkali Metal
An element in Group 1A (1), except hydrogen, that is a soft, shiny metal with one electron in its outermost energy level
Alkaline Earth Metal
An element in Group 2A (2) that has two electrons in its outermost energy level
Atom
The smallest particle of an element that retains the characteristics of the element
Atomic Mass
The weighted average mass of all the naturally occurring isotopes of an element
Atomic Mass Unit (amu)
A small mass unit used to describe the mass of extremely small particles such as atoms and subatomic particles; 1 amu is equal to one-twelfth the mass of a C-12 atom
Atomic Number
A number that is equal to the number of protons in an atom
Atomic Size
The distance between the outermost electrons and the nucleus
Atomic Symbol
An abbreviation used to indicate the mass number and atomic number of an isotope
Chemical Symbol
An abbreviation that represents the name of an element
d Block
The block of ten elements from Groups 3B (3) to 2B (12) in which electrons fill the five d orbitals in the d sub levels
Electron
A negatively charged subatomic particle having a minute mass that is usually ignored in mass calculations; its symbol is e⁻
Electron Configuration
A list of the number of electrons in each sub level within an atom, arranged by increasing energy
Energy Level
A group of electrons with similar energy
f block
The block of 14 elements in the rows at the bottom of the periodic table in which electrons fill the seven f orbitals in the 4f and 5f sub levels
Group
A vertical column in the periodic table that contains elements having similar physical and chemical properties
Group Number
A number that appears at the top of each vertical column (group) in the periodic table and indicates the number of electrons in the outermost energy level
Halogen
An element in Group 7A (7)- fluorine, chlorine, bromine, iodine, and astatine- that has seven electrons in its outermost energy level
Ionization Energy
The energy needed to remove the last tightly bound electron from the outermost energy level of an atom
Isotope
An atom that differs only in mass number from another atom of the same element. Isotopes have the same atomic number (number of protons), but different numbers of neutrons
Lewis Symbol
The representation of an atom that shows valence electrons as dots around the symbol of the element
Mass Number
The total number of protons and neutrons in the nucleus of an atom
Metal
An element that is shiny, malleable, ductile, and a good conductor of heat and electricity. The metals are located to the left of the heavy zigzag line on the periodic table
Metallic Character
A measure of how easily an element loses a valence electron
Metalloid
Elements with properties of both metals and nonmetals located along the heavy zigzag line on the periodic table
Neutron
A neutral subatomic particle having a mass of about 1 amu and found in the nucleus of an atom; its symbol is n or n⁰
Noble Gas
An element in Group 8A (18) of the periodic table, generally unreactive and seldom found in combination with other elements that has eight electrons (helium has two electrons) in its outermost energy level
Nonmetal
An element with little or no luster that is a poor conductor of heat and electricity. The nonmetals are located to the right of the heavy zigzag line on the periodic table
Nucleus
The compact, extremely dense center of an atom, containing the protons and neutrons of the atom
Orbital
The region around the nucleus where electrons of a certain energy are more likely to be found. The s orbitals are spherical, the p orbitals have two lobes
Orbital Diagram
A diagram that shows the distribution of electrons in the orbitals of the energy levels
p block
The elements in Groups 3A (13) to 8A (18) in which electrons fill the p orbitals in the p sub levels
Period
A horizontal row of elements in the periodic table
Periodic Table
An arrangement of elements by increasing atomic number such that elements having similar chemical behavior are grouped in vertical columns
Proton
A positively charged subatomic particle having a mass of about 1 amu and found in the nucleus of an atom; its symbol is p or p⁺
Representative Element
An element in the first two columns on the left of the periodic table and the last six columns on the right that has a group number of 1A through 8A or 1, 2 and 13 through 18
s block
The elements in Groups 1A (1) and 2A (2) in which electrons fill the s orbitals
Subatomic Particle
A particle within an atom; protons, neutrons, and electrons are subatomic particles
Sublevel
A group of orbitals of equal energy with an energy level. The number of sub levels in each energy level is the same as the principal quantum number (n)
Transition Element
An element in the center of the periodic table that is designated with the letter "B" or the group number of 3 through 12
Valence Electrons
Electrons in the highest energy level of an atom
Alpha Particle
A nuclear particle identical to a helium nucleus, symbol α or He²⁺
Becquerel (Bq)
A unit of activity of a radioactive sample equal to one disintegration per second
Beta Particle
A particle identical to an electron, symbol β, that forms in the nucleus when a neutron changes to a proton and an electron
Chain Reaction
A fission reaction that will continue once it has been initiated by a high-energy neutron bombarding a heavy nucleus such as uranium-235
Curie (Ci)
A unit of activity of a radioactive sample equal to 3.7 x 10^10 disintegrations/s
Decay Curve
A diagram of the decay of a radioactive element
Equivalent Dose
The measure of biological damage from an absorbed dose that has been adjusted for the type of radiation
Fission
A process in which large nuclei are split into smaller pieces, releasing large amounts of energy
Fusion
A reaction in which large amounts of energy are released when small nuclei combine to form larger nuclei
Gamma Ray
High-energy radiation emitted by an unstable nucleus
Gray (Gy)
A unit of absorbed dose equal to 100 rad
Half-life
The length of time it takes for one-half of a radioactive sample to decay
Positron
A particle of radiation with no mass and a positive charge produced when a proton is transformed into a neutron and a positron
Rad (radiation absorbed dose)
A measure of an amount of radiation absorbed by the body
Radioactive Decay
The process by which an unstable nucleus breaks down with the release of high energy radiation
Radioisotope
A radioactive atom of an element
REM (radiation equivalent in humans)
A measure of the biological damage caused by the various kinds of radiation (rad x biological factor)
Sievert (Sv)
A unit of biological damage (equivalent dose) equal to 100 rem
Anion
A negatively charged ion
Cation
A positively charged ion
Chemical Formula
The group of symbols and subscripts that represents the atoms or ions in a compound
Covalent Bond
A sharing of valence electrons by atoms
Dipole
The separation of positive and negative charges in a polar bond indicated by an arrow that is drawn from the more positive atom to the more negative atom
Dipole-Dipole Attractions
Attractive forces between oppositely charged ends of polar molecules
Dispersion Forces
Weak dipole bonding that results from a momentary polarization of non-polar molecules
Double Bond
A sharing of two pairs of electrons by two atoms
Electronegativity
The relative ability of an element to attract electrons in a bond
Hydrogen Bond
The attraction between partially positive H atom and a strongly electronegative atom of F, O, or N
Ion
An atom or group of atoms having an electrical charge because of a loss or gain of electrons
Ionic Charge
The difference between the number of protons (positive) and the number of electrons (negative) written in the upper right corner of the symbol for the element or polyatomic ion
An Ionic Compound
A compound of positive and negative ions held together by ionic bonds
Lewis Structure
A representation of a molecule or ion that shows valence electrons
Molecular Compound
A combination of atoms in which stable electron configurations are attained by sharing electrons
Molecule
The smallest unit of two or more atoms held together by covalent bonds
Non polar Covalent bond
A covalent bond in which the electrons are shared equally between atoms
Non polar Molecule
A molecule that has only non polar bonds or in which the bond dipoles cancel
Octet
A set of eight valence electrons
Octet Rule
Elements in Groups 1A-7A (1, 2, 13-17) react with other elements by forming ionic or covalent bonds to produce a stable electron configuration, usually eight electrons in the outer shell
Polar Covalent Bond
A covalent bond in which the electrons are shared unequally between atoms
Polar Molecule
A molecule containing bond dipoles that do not cancel
Polarity
A measure of the unequal sharing of electrons indicated by the difference in electronegativities
Polyatomic Ion
A group of covalently bonded nonmetal atoms that has an overall electrical charge
Triple Bond
A sharing of three pairs of electrons by two atoms
Valence Shell Electron-Pair Repulsion (VSEPR) Theory
A theory that predicts the shape of a molecule by placing the electron pairs on a central atom as far apart as possible to minimize the mutual repulsion of the electrons
Actual yield
The actual amount of product produced by a reaction
Avogadro's Number
The number of items in one mole, equal to 6.02 x 10^23
Balanced Equation
The final form of a chemical equation that shows the same number of atoms of each element in the reactants and products
Chemical Equation
A shorthand way to represent a chemical reaction using chemical formulas to indicate the reactants and products and coefficients to show reacting ratios
Coefficients
Whole numbers placed in front of the formulas to balance the number of atoms or moles of atoms of each element on both sides of an equation
Combination Reaction
A chemical reaction in which reactants combine to form a single product
Combustion Reaction
A chemical reaction in which a fuel containing carbon and hydrogen reacts with oxygen to produce CO2, H2O, and energy
Decomposition Reaction
A reaction in which a single reactant splits into two or more simpler substances
Double Replacement Reaction
A reaction in which parts of two different reactants exchange places
Endothermic Reaction
A reaction that requires heat; the energy of the products is higher than the energy of the reactants
Exothermic Reaction
A reaction that releases heat; the energy of the products is lower than there energy of the reactants
Formula Unit
The group of ions represented by the formula of an ionic compound
Heat of Reaction
The heat (symbol ΔH) absorbed or released when a reaction takes place at constant pressure
Limiting Reactant
The reactant used up during a chemical reaction, which limits the amount of product that can form
Molar Mass
The mass in grams of 1 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 multiplied by their subscripts in the formula
Mole
A group of atoms, molecules, or formula units that contains 6.02 x 10^23 of these items
Mole-mole Factor
A conversion factor that relates the number of moles of two compounds derived from the coefficients in an equation
Oxidation
The loss of electrons by a substance. Biological oxidation may involve the addition of oxygen or the loss of hydrogen
Oxidation-Reduction Reaction
A reaction in which the oxidation of one reactant is always accompanied by the reduction of another reactant
Percent Yield
The ratio of the actual yield for a reaction to the theoretical field possible for the reaction
Products
The substances formed as a result of a chemical reaction
Reactants
The initial substances that undergo change in a chemical reaction
Reduction
The gain of electrons by a substance. Biological reduction may involve the loss of oxygen or the gain of hydrogen
Single Replacement Reaction
A reaction in which an element replaces a different element in a compound
Theoretical Yield
The maximum amount of product that a reaction can produce from a given amount of reactant q
Atmosphere (atm)
A unit equal to pressure exerted by a column of mercury 760 mm high
Atmospheric Pressure
The pressure exerted by the atmosphere
Avogadro's Law
A gas law stating that the volume of a gas is directly related to the number of moles of gas when pressure and temperature do not change
Boyle's Law
A gas law stating that the pressure of a gas is inversely related to the volume when temperature and moles of the gas do not change
Charle's Law
A gas law stating that the volume of a gas changes directly with a change in Kelvin temperature when pressure and moles of the gas do not change
Combined Gas Law
A relationship that combines several gas laws relating pressure, volume, and temperature when the amount of gas does not change
Dalton's Law
A gas law stating that the total pressure exerted by a mixture of gases in a container is the sum of the partial pressures that each gas would exert
Gay-Lussac's Law
A gas law stating that the pressure of a gas changes directly with a change in the Kelvin temperature when the number of moles of a gas and its volume do not change
Ideal Gas Constant, R
A numerical value that relates the quantities P, V, n and T in the ideal gas law, PV= nRT
kinetic Molecular Theory of Gases
A model used to explain the behavior of gases
Molar Volume
A volume of 22.4 L occupied by 1 mole of a gas at STP conditions of 0 °C (273 K) and 1 atm
Partial Pressure
The pressure exerted by a single gas in a gas mixture
Pressure
The force exerted by gas particles that hit the walls of a container
STP
Standard conditions of exactly 0 °C (273 K) temperature and 1 atm pressure used for the comparison of gases
Vapor Pressure
The pressure exerted by the particles of vapor above a liquid
Colloid
A mixture having particles that are moderately large. Colloids pass through filters but cannot pass through semipermeable membranes
Concentration
A measure of the amount of solute that is dissolved in a specified amount of solution
Crenation
The shriveling of a cell because water leaves the cell when the cell is placed in a hypertonic solution
Dialysis
A process in which water and small solute particles pass through a semipermeable membrane
Dilution
A process by which water (solvent) is added to a solution to increase the volume and decrease (dilute) the concentration of the solute
Electrolyte
A substance that produces ions when dissolved in water; its solution conducts electricity
Equivalent (Eq)
The amount of a positive or negative ion that supplies 1 mole of electrical charge
Hemodialysis
A mechanical cleansing of the blood by an artificial kidney using the principle of dialysis
Hemolysis
A swelling and bursting of red blood cells in a hypotonic solution because of an increase in fluid volume
Henry's Law
The solubility of a gas in a liquid is directly related to the pressure of that gas above the liquid
Hydration
The process of surrounding dissolved ions by water molecules
Hypertonic Solution
A solution that has higher particle concentration and higher osmotic pressure than the cells of the body
Hypotonic Solution
A solution that has a lower particle concentration and lower osmotic pressure than the cells of the body
Isotonic Solution
A solution that has the same particle concentration and osmotic pressure as that of the cells of the body
Mass Percent (m/m)
The grams of solute in exactly 100 g of solution
Mass/volume percent (m/v)
The grams of solute in exactly 100 mL of solution
Molarity
The number of moles of solute in exactly 1 L of solution
Non electrolyte
A substance that dissolves in eater as molecules; its solution does not conduct an electrical current
Osmosis
The flow of a solvent, usually water, through a semipermeable membrane into a solution of higher solute concentration
Osmotic Pressure
The pressure that prevents the low of water into the more concentrated solution
Saturated Solution
A solution containing the maximum amount of solute that can dissolve at a given temperature. Any additional solute will remain undissolved in the container
Solubility
The maximum amount of solute that can dissolve in exactly 100 g of solvent, usually water, at a given temperature
Solubility Rules
A set of guidelines that states whether an ionic compound is soluble or insoluble in water
Solute
The component in a solution that is present in the lesser amount
Solution
A homogeneous mixture in which the solute is made up of small particles (ions or molecules) that can pass through filters and semipermeable membranes
Solvent
The substance in which the solute dissolves; usually the component present in greater amount
Strong Electrolyte
A compound that ionizes completely when it dissolves in water. Its solution is a good conductor of electricity
Suspension
A mixture in which the solute particles are large enough and heavy enough to settle out and be retained by both filters and semipermeable membranes
Unsaturated Solution
A solution that contains less solute than can be dissolved
Volume Percent (v/v)
A percent concentration that relates the volume of the solute in exactly 100 mL of solution
Weak Electrolyte
A substance that produces only a few ions along with many molecules when it dissolves in water. Its solution is a weak conductor of electricity
Activation Energy
The energy that must be provided by a collision to break apart the bonds of the reacting molecules
Catalyst
A substance that increases the rate of reaction by lowering the activation energy
Chemical Equilibrium
The point at which the rate of forward and reverse reactions are equal so that no further change in concentrations of reactants and products take place
Collision Theory
A model for a chemical reaction stating that molecules must collide with sufficient energy and proper orientation to form products
Equilibrium Constant, Kc
Th numerical value obtained by substituting the equilibrium concentrations of the components into the equilibrium constant expression
Equilibrium Constant Expression
The ratio of the concentrations of products to the concentrations of reactants, with each component raised to an exponent equal to the coefficient of that compound in the balanced chemical equation
Le Chatelier's Principle
When a stress is placed on a system at equilibrium, the equilibrium shifts to relieve that stress
Rate of Reaction
The speed at which reactants are used to form product(s)
Reversible Reaction
A reaction in which a forward reaction occurs from reactants to products, and a reverse reaction occurs from products back to reactants
Acid
A substance that dissolves in water and produces hydrogen ions (H+), according to the Arrhenius theory. All acids are hydrogen ion donors, according to the Broasted-Lowry theory
Acid Dissociation Constant, Ka
The numerical value of the product of ions from the dissociation of a weak acid divided by the concentration of the weak acid
Amphoteric
Substances that can act as either an acid or a base in water
Base
A substance that dissolves in water and produces hydroxide ions (OH-) according to the Arrhenius theory. All bases are hydrogen ion acceptors, according to the Broasted-Lowry theory
Base Dissociation Constant, (Kb)
The numerical value of the product of the ions from the dissociation of a weak base divided by the concentration of the weak base
Broasted-Lowry Acids and Bases
An acid is a hydrogen ion donor; a base is a hydrogen ion acceptor
Buffer Solution
A solution of a weak acid and its conjugate base or a weak base and its conjugate acid that maintains the pH y neutralizing added acid or base
Conjugate acid-base
An acid and a base that differ by one H+. When an acid donates a hydrogen ion, the product is its conjugate base, which is capable of accepting a hydrogen ion in the reverse reaction
Dissociation
The separation of an acid or a base into ions in water
Endpoint
The point at which an indicator changes color. Fr the indicator phenolphthalein, the color change occurs when the number of moles of OH- is equal to the number of moles of H3O+ in the sample
Hydronium Ion, H3O+
The ion formed by the attraction of a hydrogen ion, H+, to a water molecule
Indicator
A substance added to a titration sample that changes color when the pH of the solution changes
Neutral
The term that describes a solution with equal concentrations of [H3O+] and [OH-]
Neutralization
A reaction between an acid and a base to form water
pH
A measure of the [H3O+] in a solution;
Salt
An ionic compound that contains a metal ion or NH4+ and a nonmetal or polyatomic ion other than OH-
Strong Acid
An acid that completely dissociates in water
Strong Base
A base that completely dissociates in water
Titration
The addition of base to an acid sample to determine the concentration of the acid
Water Dissociation Constant Expression, Kw
The product of [H3O+] and [OH-] in a solution;
Weak Acid
An acid that is a poor donor of H+ and dissociates only slightly in water
Weak Base
A base that is a poor acceptor of H+ and produces only a small number of ions in water