Chemistry: matter and change

Applied Research
research that is directed toward a practical goal or application, research undertaken to solve a specific problem

Chemistry
The scientific study of matter and the changes it undergoes

Conclusion
a judgment based on the information obtained

Control
In an experiment, the standard used for comparison.

Dependent Variable
in an experiment, the variable whose value depends on the independent variable

Experiment
a set of controlled observations that test the hypothesis

Hypothesis
a tentative, testable statement or prediction about what has been observed

Independent Variable
in an experiment, the variable that the experimenter plans to change

Mass
a measure of the amount of matter

Matter
anything that has mass and takes up space

Model
a visual, verbal, and/or mathematical explanation of data collected from many experiments

Pure Research
a type of scientific investigation that seeks to gain knowledge for the sake of knowledge itself

Qualitative Data
information describing color, odor, shape, or some other physical characteristic

Quantitative Data
numerical information describing how much, how little, how big, how tall, how fast, etc.

Scientific Law
describes a relationship in nature that is supported by many experiments

Scientific Method
a systematic approach used in scientific study that typically includes observation, a hypothesis, experiments, data analysis, and a conclusion

Technology
the practical use of scientific information

Theory
an explanation supported by many experiments; still subject to new data and can be modified

Weight
a measure of the amount of matter and also the effect of Earth’s gravitational pull on the matter

accuracy
refers to how close a measured value is to an accepted value

base unit
a defined unit in a system of measurement that is based on an object or event in the physical world and is independent of other units

conversion factor
a ratio of equivalent values used to express the same quantity in different units

density
a ratio that compares the mass of an object to its volume

derived unit
a unit defined by a combination of base unit

dimensional analysis
a problem solving method that focuses on the units that are used to describe matter

graph
a visual representation of information that can reveal patterns in data

kelvin
the SI base unit of temperature

kilogram
the SI base unit for mass

liter
the metric unit for volume equal to one cubic decimeter

meter
the SI base unit for length

percent error
the ratio of an error to an accepted value

precision
refers to how close a series of measurements are to one another

scientific notation
expresses numbers as a multiple of two factors – a number between 1 and 10, and 10 raised to a power or exponent

second
the SI base unit for time

significant figure
the number of all known digits reported in measurements plus one estimated digit

chemical change
a process involving one or more substances changing into new substances

chemical property
the ability or inability of a substance to combine with or change into one or more new substances

compound
a chemical combination of two or more different elements

element
a pure substance that cannot be broken down into simpler substances

gas
a form of matter that flows to conform to the shape of its container, fills the container’s volume, and is easily compressed

heterogeneous mixture
one that does not have a uniform composition and in which the individual substances remain distinct

homogeneous mixture
one that has a uniform composition throughout and always has a single phase

law of conservation of mass
states that mass is neither created nor destroyed during a chemical reaction but is conserved

law of definite proportions
states that, regardless of the amount, a compound is always composed of the same elements in the same proportion by mass

liquid
a form of matter that flows, has constant volume, and takes the shape of its container

mixture
a physical blend of two or more pure substances in any proportion in which each substance retains its individual properties; can be separated by physical means

percent by mass
a percentage determined by the ratio of the mass of each element to the total mass of the compound

periodic table
a chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups) arranged by increasing atomic number

physical change
a type of change that alters the physical properties of a substance but does not change its composition

physical property
a characteristic of matter that can be observed or measured without changing the sample’s composition

solid
a form of matter that has its own definite shape and volume, is incompressible, and expands only slightly when heated

solution
a uniform mixture that may contain solids, liquids, or gases

states of matter
the physical forms in which all matter naturally exists on Earth – most commonly solid, liquid, and gas

substance
a form of matter that has a uniform and unchanging composition

vapor
gaseous state of a substance that is a liquid or a solid at room temperature

amplitude
the height of a wave from the origin to a crest

atomic emission spectrum
the frequencies of light emitted by an element separated into discrete lines

atomic orbital
a 3D region around the nucleus of an atom that describes an electron’s probable location

aufbau principal
states that each electron occupies the lowest energy orbital available

electromagnetic radiation
a form of energy that exhibits wavelike behavior as it travels through space

electromagnetic spectrum
includes all forms of electromagnetic radiation, with the only differences in the types of radiation being their frequencies and wavelengths

electron configuration
the arrangement of electrons in an atom

electron-dot structure
consists of an element’s symbol (representing the nucleus & inner electrons) that is surrounded by dots representing the atom’s valence electrons

energy sublevel
the energy levels contained within a principle energy level.

frequency
the number of waves that pass a given point per second

ground state
the lowest allowable energy state of an atom

Heisenberg uncertainty principle
states that it is not possible to know precisely both the velocity and the position of a particle at the same time

Hund’s rule
single electrons with the same spin must occupy each orbital before additional electrons with opposite spins can occupy the same orbital

Pauli exclusion principle
states that a maximum of two electrons may occupy the same orbital, but only if the electrons have opposite spins

photoelectric effect
the emission of electrons from a metal when light shines on the metal

photon
a particle of electromagnetic radiation with no mass that carries a quantum of energy

Planck’s constant
h, which has a value of 6.6261×10^-34 Js, where J is the symbol for Joules

principal energy levels
the major energy levels of an atom

principal quantum number
n, which in the quantum mechanical model indicates the relative sizes and energies of atomic orbitals

quantum
the minimum amount of energy that can be gained or lost by an atom

quantum mechanical model of the atom
an atomic model in which electrons are treated as waves

valence electron
the electrons in an atom’s outermost orbitals

wavelength
the shortest distance between equivalent points on a continuous wave

alkali metal
group 1A elements, except hydrogen, that are on the left side of the modern periodic table

alkaline earth metal
group 2A elements in the modern periodic table

electronegativity
ability of an atom to attract electrons when the atom is in a compound

group
a vertical column of elements in the periodic table; also called a family

halogen
a highly reactive group 7A element

inner transition metal
a type of group B element that is contained in the f-block of the periodic table

ion
an atom or bonded group of atoms with a positive or negative charge

ionization energy
energy required to remove an electron from an atom

metal
an element that is a solid at room temperature, a good conductor of heat and electricity, and generally shiny

metalloid
an element, such as silicon or germanium, that has physical and chemical properties of both metals and nonmetals

noble gas
an extremely unreactive group 8A element

nonmetal
elements that are generally gases or dull, brittle solids that are poor conductors of heat and electricity

period
a horizontal row of elements in the modern periodic table

periodic law
states that when the elements are arranged by increasing atomic number, there is periodic repetition of their chemical and physical properties

representative elements
groups of elements in the modern periodic table that are designated with an A (1A through 8A) and possess a wide range of chemical and physical properties

transition metal
a type of group B element that is contained in the d-block of the periodic table

transition elements
groups of elements in the modern periodic table that are designated with a B(1B through 8B) and are further divided into transition metals and inner transition metals

cation
positive ion; formed by metallic elements

anion
negative ion; mostly formed by nonmetal elements

covalent bond
a bond that results from the sharing of valence electrons

endothermic
chemical reaction in which a greater amount of energy is required to break the existing bonds in reactants than is released when the new bonds form in product molecules

exothermic
a chemical reaction in which more energy is released that is required to break bonds in the initial reaction

Lewis structure
a model that uses electron-dot structures to show how electrons are arranged in molecules

molecule
forms when two or more atoms covalently bond; usually includes two or more nonmetals

polar covalent
a type of bond that forms when electrons are not shared equally

structural formula
a molecular model that uses symbols and bonds to show relative positions of atoms

VSEPR model
model based on an arrangement that minimizes the repulsion of shared and unshared pairs of electrons around the central atom

alloy
a mixture of elements that has metallic properties

chemical bond
the force that holds two atoms together

delocalized electrons
the electrons involved in metallic bonding that are free to move easily from one atom to the next throughout the metal and are not attached to a particular atom

formula unit
the simplest ratio of ions represented in an ionic compound

ionic bond
the electrostatic force that holds oppositely charged particles together; usually a nonmetal paired with a metal

metallic bond
the attraction of a metallic cation for delocalized electrons

monatomic ion
ion formed from only one atom

oxidation number
the positive or negative charge of a monatomic ion

polyatomic ion
an ion made up of two or more atoms bonded together that acts as a single unit with a net charge

aqueous solution
a solution in which the solvent is water

chemical equation
a statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction

chemical reaction
the process by which the atoms of one or more substances are rearranged to form different substances

coefficient
the number written in front of a reactant or product in a chemical equation

combustion reaction
a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light

decomposition reaction
a chemical reaction that occurs when a single compound breaks down into two or more elements

double replacement reaction
a chemical reaction that involves the exchange of positive ions between two compounds and produces either a precipitate, a gas, or water

precipitate
a solid produced during a chemical reaction in a solution

product
a substance formed during a chemical reaction

reactant
the starting substance in a chemical reaction

single replacement reaction
a chemical reaction that occurs when the atoms of one element replace the atoms of another element in a compound

solute
a substance dissolved in a solution

solvent
the substance that dissolves a solute to form a solution

synthesis reaction
a chemical reaction in which two or more substances react to yield a single product

Avagadro’s number
6.02 x 10^23, which represents the number of particles in a mole

empirical formula
a formula that shows the smallest whole number mole ratio of the elements of a compound and may/may not be the same as the actual molecular formula

hydrate
a compound that has a specific number of water molecules bound to its atoms

molar mass
the mass in grams of one mole of any pure substance

mole
the SI unit used to measure the amount of a substance

molecular formula
a formula that specifies the actual number of atoms of each element in one molecule or formula unit of a substance

percent composition
the percent by mass of each element in a compound

Avogadro’s principle
if temperature and pressure are constant, gases with the same volume will then have the same number of particles

Boyle’s law
if temperature is constant, volume and pressure are inversely proportional

Charles’s law
if pressure is constant, volume and temperature are directly proportional

combined gas law
combines Boyle’s, Charles’s, and Gay-Lussac’s law to show the relationship between pressure, volume, and temperature for a fixed amount of gas

Gay-Lussac’s law
if volume is constant, pressure and temperature are directly proportional

ideal gas constant
an experimentally determined constant whose value in the ideal gas equation depends on the units that are used for pressure

ideal gas law
describes the behavior of an ideal gas in terms of temperature, volume, and pressure, and number of moles of gas present

molar volume
the volume that gas occupies at zero degrees Celsius and 1.0 atmospheres (STP); 22.4L

calorie
the amount of heat required to raise the temperature of one gram of pure water by one degree Celsius

calorimeter
an insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process

chemical potential energy
energy stored in a substance because of its composition

energy
the capacity to do work or produce heat

enthalpy
the heat content of a system at constant pressure

entropy
a measure of disorder or randomness of the particles of a system

free energy
energy available to do work

heat
a form of energy that flows from a warmer object to a cooler object

Hess’s law
two or more thermochemical equations can be added to produce a final equation for a reaction

joule
the SI unit for heat

law of conservation of energy
energy may change from one form or another, but is neither created nor destroyed

law of disorder
entropy of the universe must increase as a result of a spontaneous reaction

heat of fusion
the amount of heat required to melt one mole of a solid substance

heat of vaporization
the amount of heat required to evaporate one mole of a liquid

specific heat
amount of heat required to raise the temperature of one gram of a given substance by one degree Celsius

surrounding
includes everything in the universe except the system

system
the specific part of the universe containing the reaction or the process being studied

thermochemical equation
a balanced chemical equation that includes the physical states of all the reactants and products and specifies the change in enthalpy

thermochemistry
the study of heat changes that accompany chemical reactions and phase changes

universe
the system plus the surrounding

activation energy
the minimum amount of energy required to start a chemical reaction

catalyst
a substance that initiates or accelerates a chemical reaction without itself being affected

collision theory
states that chemical reactions occur through collisions between molecules or atoms

complex reaction
A chemical reaction that consists of two or more elementary steps.

instantaneous rate
The rate of decomposition at a specific time, calculated from the rate law, the specific rate constant, and the concentrations of all the reactants.

intermediate
A substance formed in one elementary step of a complex reaction and consumed in another

rate-determining step
the slowest elementary step in a complex reaction

rate law
an equation that relates reaction rate and concentrations of reactants

reaction mechanism
a series of elementary reactions that take place during the course of a complex reaction

reaction order
defines how rate is affected by concentration of that reactant

reaction rate
the change in concentration of reactants or products per unit time as a reaction proceeds

concentration
describes how much solute is present in a solution compared to the amount of solvent

molality
the concentration of a solution expressed in moles of solute per kilogram of solvent

molarity
concentration measured by the number of moles of solute per liter of solvent

solubility
the maximum amount of solute that will dissolve in a given amount of time at a specific temperature and pressure

soluble
capable of being dissolved in a given substance

saturated solution
contains the maximum amount of dissolved solute for a given amount of solvent at a specific temperature and pressure

unsaturated solution
a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute

supersaturated solution
contains more dissolved solute than a saturated solution at the same temperature

solute
the dissolved substance in a solution

solvent
a liquid substance capable of dissolving other substances

chemical equilibrium
a chemical reaction and its reverse proceed at equal rates

equilibrium constant
describes the ratio of product concentrations to reactant concentrations raised to the power indicated by the coefficients

Le Chatelier’s Principle
a change in any of the factors determining equlibrium will cause the system to adjust to reduce the effect of the change

reversible reaction
A chemical reaction in which the products re-form the original reactants

acidic solution
a solution whose pH is less than 7

Arrhenius model
An acid is a substance that contains hydrogen and ionizes to produce hydrogen ions in aqueous solution; A base is a substance that contains a hydroxide group and dissociates to produce a hydroxide ion in aqueous solution

basic solution
a solution whose pH is greater than 7

Bronsted-Lowry model
a model of acids and bases in which an acid is a hydrogen ion donor and a base is a hydrogen ion acceptor

buffer
an ionic compound that resists changes in its pH

conjugate acid
the particle formed when a base gains a hydrogen ion

conjugate base
the particle that remains when an acid has donated a hydrogen ion

neutralization reaction
the reaction of an acid and a base to form a neutral solution of water and a salt

pH
the negative logarithm of the hydrogen ion concentration of a solution

pOH
the negative logarithm of the hydroxide ion concentration of a solution

strong acid
an acid that ionizes completely in aqueous solution

strong base
A base that dissociates completely into ions in solution.

titration
process in which a solution of known concentration is used to determine the concentration of another solution

weak acid
an acid that is only slightly ionized in aqueous solution

weak base
A base that does not dissociate completely into ions in solution.