Chemistry: matter and change – Flashcards
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Dependent Variable
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in an experiment, the variable whose value depends on the independent variable
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Experiment
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a set of controlled observations that test the hypothesis
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Hypothesis
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a tentative, testable statement or prediction about what has been observed
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Independent Variable
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in an experiment, the variable that the experimenter plans to change
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Mass
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a measure of the amount of matter
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Matter
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anything that has mass and takes up space
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Model
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a visual, verbal, and/or mathematical explanation of data collected from many experiments
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Pure Research
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a type of scientific investigation that seeks to gain knowledge for the sake of knowledge itself
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Qualitative Data
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information describing color, odor, shape, or some other physical characteristic
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Quantitative Data
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numerical information describing how much, how little, how big, how tall, how fast, etc.
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Scientific Law
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describes a relationship in nature that is supported by many experiments
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Scientific Method
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a systematic approach used in scientific study that typically includes observation, a hypothesis, experiments, data analysis, and a conclusion
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Technology
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the practical use of scientific information
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Theory
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an explanation supported by many experiments; still subject to new data and can be modified
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Weight
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a measure of the amount of matter and also the effect of Earth's gravitational pull on the matter
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accuracy
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refers to how close a measured value is to an accepted value
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base unit
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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
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conversion factor
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a ratio of equivalent values used to express the same quantity in different units
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density
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a ratio that compares the mass of an object to its volume
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derived unit
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a unit defined by a combination of base unit
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dimensional analysis
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a problem solving method that focuses on the units that are used to describe matter
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graph
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a visual representation of information that can reveal patterns in data
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kelvin
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the SI base unit of temperature
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kilogram
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the SI base unit for mass
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liter
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the metric unit for volume equal to one cubic decimeter
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meter
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the SI base unit for length
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percent error
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the ratio of an error to an accepted value
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precision
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refers to how close a series of measurements are to one another
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scientific notation
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expresses numbers as a multiple of two factors - a number between 1 and 10, and 10 raised to a power or exponent
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second
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the SI base unit for time
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significant figure
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the number of all known digits reported in measurements plus one estimated digit
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chemical change
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a process involving one or more substances changing into new substances
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chemical property
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the ability or inability of a substance to combine with or change into one or more new substances
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compound
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a chemical combination of two or more different elements
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element
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a pure substance that cannot be broken down into simpler substances
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gas
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a form of matter that flows to conform to the shape of its container, fills the container's volume, and is easily compressed
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heterogeneous mixture
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one that does not have a uniform composition and in which the individual substances remain distinct
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homogeneous mixture
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one that has a uniform composition throughout and always has a single phase
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law of conservation of mass
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states that mass is neither created nor destroyed during a chemical reaction but is conserved
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law of definite proportions
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states that, regardless of the amount, a compound is always composed of the same elements in the same proportion by mass
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liquid
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a form of matter that flows, has constant volume, and takes the shape of its container
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mixture
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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
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percent by mass
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a percentage determined by the ratio of the mass of each element to the total mass of the compound
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periodic table
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a chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups) arranged by increasing atomic number
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physical change
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a type of change that alters the physical properties of a substance but does not change its composition
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physical property
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a characteristic of matter that can be observed or measured without changing the sample's composition
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solid
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a form of matter that has its own definite shape and volume, is incompressible, and expands only slightly when heated
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solution
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a uniform mixture that may contain solids, liquids, or gases
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states of matter
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the physical forms in which all matter naturally exists on Earth - most commonly solid, liquid, and gas
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substance
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a form of matter that has a uniform and unchanging composition
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vapor
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gaseous state of a substance that is a liquid or a solid at room temperature
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amplitude
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the height of a wave from the origin to a crest
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atomic emission spectrum
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the frequencies of light emitted by an element separated into discrete lines
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atomic orbital
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a 3D region around the nucleus of an atom that describes an electron's probable location
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aufbau principal
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states that each electron occupies the lowest energy orbital available
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electromagnetic radiation
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a form of energy that exhibits wavelike behavior as it travels through space
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electromagnetic spectrum
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includes all forms of electromagnetic radiation, with the only differences in the types of radiation being their frequencies and wavelengths
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electron configuration
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the arrangement of electrons in an atom
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electron-dot structure
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consists of an element's symbol (representing the nucleus & inner electrons) that is surrounded by dots representing the atom's valence electrons
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energy sublevel
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the energy levels contained within a principle energy level.
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frequency
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the number of waves that pass a given point per second
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ground state
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the lowest allowable energy state of an atom
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Heisenberg uncertainty principle
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states that it is not possible to know precisely both the velocity and the position of a particle at the same time
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Hund's rule
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single electrons with the same spin must occupy each orbital before additional electrons with opposite spins can occupy the same orbital
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Pauli exclusion principle
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states that a maximum of two electrons may occupy the same orbital, but only if the electrons have opposite spins
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photoelectric effect
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the emission of electrons from a metal when light shines on the metal
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photon
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a particle of electromagnetic radiation with no mass that carries a quantum of energy
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Planck's constant
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h, which has a value of 6.6261x10^-34 Js, where J is the symbol for Joules
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principal energy levels
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the major energy levels of an atom
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principal quantum number
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n, which in the quantum mechanical model indicates the relative sizes and energies of atomic orbitals
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quantum
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the minimum amount of energy that can be gained or lost by an atom
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quantum mechanical model of the atom
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an atomic model in which electrons are treated as waves
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valence electron
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the electrons in an atom's outermost orbitals
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wavelength
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the shortest distance between equivalent points on a continuous wave
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alkali metal
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group 1A elements, except hydrogen, that are on the left side of the modern periodic table
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alkaline earth metal
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group 2A elements in the modern periodic table
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electronegativity
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ability of an atom to attract electrons when the atom is in a compound
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group
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a vertical column of elements in the periodic table; also called a family
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halogen
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a highly reactive group 7A element
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inner transition metal
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a type of group B element that is contained in the f-block of the periodic table
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ion
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an atom or bonded group of atoms with a positive or negative charge
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ionization energy
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energy required to remove an electron from an atom
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metal
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an element that is a solid at room temperature, a good conductor of heat and electricity, and generally shiny
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metalloid
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an element, such as silicon or germanium, that has physical and chemical properties of both metals and nonmetals
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noble gas
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an extremely unreactive group 8A element
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nonmetal
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elements that are generally gases or dull, brittle solids that are poor conductors of heat and electricity
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period
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a horizontal row of elements in the modern periodic table
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periodic law
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states that when the elements are arranged by increasing atomic number, there is periodic repetition of their chemical and physical properties
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representative elements
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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
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transition metal
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a type of group B element that is contained in the d-block of the periodic table
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transition elements
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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
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cation
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positive ion; formed by metallic elements
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anion
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negative ion; mostly formed by nonmetal elements
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covalent bond
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a bond that results from the sharing of valence electrons
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endothermic
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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
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exothermic
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a chemical reaction in which more energy is released that is required to break bonds in the initial reaction
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Lewis structure
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a model that uses electron-dot structures to show how electrons are arranged in molecules
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molecule
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forms when two or more atoms covalently bond; usually includes two or more nonmetals
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polar covalent
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a type of bond that forms when electrons are not shared equally
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structural formula
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a molecular model that uses symbols and bonds to show relative positions of atoms
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VSEPR model
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model based on an arrangement that minimizes the repulsion of shared and unshared pairs of electrons around the central atom
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alloy
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a mixture of elements that has metallic properties
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chemical bond
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the force that holds two atoms together
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delocalized electrons
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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
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formula unit
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the simplest ratio of ions represented in an ionic compound
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ionic bond
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the electrostatic force that holds oppositely charged particles together; usually a nonmetal paired with a metal
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metallic bond
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the attraction of a metallic cation for delocalized electrons
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monatomic ion
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ion formed from only one atom
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oxidation number
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the positive or negative charge of a monatomic ion
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polyatomic ion
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an ion made up of two or more atoms bonded together that acts as a single unit with a net charge
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aqueous solution
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a solution in which the solvent is water
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chemical equation
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a statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction
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chemical reaction
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the process by which the atoms of one or more substances are rearranged to form different substances
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coefficient
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the number written in front of a reactant or product in a chemical equation
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combustion reaction
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a chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light
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decomposition reaction
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a chemical reaction that occurs when a single compound breaks down into two or more elements
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double replacement reaction
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a chemical reaction that involves the exchange of positive ions between two compounds and produces either a precipitate, a gas, or water
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precipitate
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a solid produced during a chemical reaction in a solution
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product
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a substance formed during a chemical reaction
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reactant
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the starting substance in a chemical reaction
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single replacement reaction
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a chemical reaction that occurs when the atoms of one element replace the atoms of another element in a compound
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solute
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a substance dissolved in a solution
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solvent
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the substance that dissolves a solute to form a solution
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synthesis reaction
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a chemical reaction in which two or more substances react to yield a single product
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Avagadro's number
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6.02 x 10^23, which represents the number of particles in a mole
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empirical formula
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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
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hydrate
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a compound that has a specific number of water molecules bound to its atoms
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molar mass
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the mass in grams of one mole of any pure substance
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mole
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the SI unit used to measure the amount of a substance
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molecular formula
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a formula that specifies the actual number of atoms of each element in one molecule or formula unit of a substance
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percent composition
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the percent by mass of each element in a compound
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Avogadro's principle
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if temperature and pressure are constant, gases with the same volume will then have the same number of particles
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Boyle's law
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if temperature is constant, volume and pressure are inversely proportional
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Charles's law
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if pressure is constant, volume and temperature are directly proportional
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combined gas law
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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
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Gay-Lussac's law
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if volume is constant, pressure and temperature are directly proportional
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ideal gas constant
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an experimentally determined constant whose value in the ideal gas equation depends on the units that are used for pressure
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ideal gas law
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describes the behavior of an ideal gas in terms of temperature, volume, and pressure, and number of moles of gas present
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molar volume
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the volume that gas occupies at zero degrees Celsius and 1.0 atmospheres (STP); 22.4L
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calorie
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the amount of heat required to raise the temperature of one gram of pure water by one degree Celsius
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calorimeter
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an insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process
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chemical potential energy
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energy stored in a substance because of its composition
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energy
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the capacity to do work or produce heat
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enthalpy
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the heat content of a system at constant pressure
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entropy
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a measure of disorder or randomness of the particles of a system
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free energy
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energy available to do work
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heat
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a form of energy that flows from a warmer object to a cooler object
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Hess's law
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two or more thermochemical equations can be added to produce a final equation for a reaction
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joule
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the SI unit for heat
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law of conservation of energy
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energy may change from one form or another, but is neither created nor destroyed
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law of disorder
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entropy of the universe must increase as a result of a spontaneous reaction
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heat of fusion
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the amount of heat required to melt one mole of a solid substance
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heat of vaporization
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the amount of heat required to evaporate one mole of a liquid
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specific heat
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amount of heat required to raise the temperature of one gram of a given substance by one degree Celsius
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surrounding
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includes everything in the universe except the system
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system
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the specific part of the universe containing the reaction or the process being studied
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thermochemical equation
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a balanced chemical equation that includes the physical states of all the reactants and products and specifies the change in enthalpy
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thermochemistry
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the study of heat changes that accompany chemical reactions and phase changes
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universe
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the system plus the surrounding
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activation energy
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the minimum amount of energy required to start a chemical reaction
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catalyst
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a substance that initiates or accelerates a chemical reaction without itself being affected
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collision theory
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states that chemical reactions occur through collisions between molecules or atoms
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complex reaction
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A chemical reaction that consists of two or more elementary steps.
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instantaneous rate
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The rate of decomposition at a specific time, calculated from the rate law, the specific rate constant, and the concentrations of all the reactants.
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intermediate
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A substance formed in one elementary step of a complex reaction and consumed in another
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rate-determining step
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the slowest elementary step in a complex reaction
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rate law
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an equation that relates reaction rate and concentrations of reactants
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reaction mechanism
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a series of elementary reactions that take place during the course of a complex reaction
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reaction order
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defines how rate is affected by concentration of that reactant
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reaction rate
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the change in concentration of reactants or products per unit time as a reaction proceeds
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concentration
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describes how much solute is present in a solution compared to the amount of solvent
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molality
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the concentration of a solution expressed in moles of solute per kilogram of solvent
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molarity
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concentration measured by the number of moles of solute per liter of solvent
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solubility
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the maximum amount of solute that will dissolve in a given amount of time at a specific temperature and pressure
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soluble
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capable of being dissolved in a given substance
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saturated solution
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contains the maximum amount of dissolved solute for a given amount of solvent at a specific temperature and pressure
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unsaturated solution
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a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute
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supersaturated solution
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contains more dissolved solute than a saturated solution at the same temperature
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solute
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the dissolved substance in a solution
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solvent
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a liquid substance capable of dissolving other substances
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chemical equilibrium
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a chemical reaction and its reverse proceed at equal rates
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equilibrium constant
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describes the ratio of product concentrations to reactant concentrations raised to the power indicated by the coefficients
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Le Chatelier's Principle
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a change in any of the factors determining equlibrium will cause the system to adjust to reduce the effect of the change
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reversible reaction
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A chemical reaction in which the products re-form the original reactants
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acidic solution
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a solution whose pH is less than 7
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Arrhenius model
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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
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basic solution
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a solution whose pH is greater than 7
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Bronsted-Lowry model
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a model of acids and bases in which an acid is a hydrogen ion donor and a base is a hydrogen ion acceptor
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buffer
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an ionic compound that resists changes in its pH
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conjugate acid
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the particle formed when a base gains a hydrogen ion
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conjugate base
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the particle that remains when an acid has donated a hydrogen ion
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neutralization reaction
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the reaction of an acid and a base to form a neutral solution of water and a salt
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pH
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the negative logarithm of the hydrogen ion concentration of a solution
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pOH
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the negative logarithm of the hydroxide ion concentration of a solution
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strong acid
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an acid that ionizes completely in aqueous solution
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strong base
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A base that dissociates completely into ions in solution.
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titration
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process in which a solution of known concentration is used to determine the concentration of another solution
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weak acid
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an acid that is only slightly ionized in aqueous solution
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weak base
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A base that does not dissociate completely into ions in solution.
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