chemistry midterm exam study guide – Flashcards
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Scientific method
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a systematic approach used in scientfic study; an organizd process used by scientists to do research and verify the work of others
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Hypothesis
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A tentative, etstable statement or prediction about what has been observed
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experiment
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A set of controlled observations that test a hypothesis
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Control
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in an experiment, the standard that is used for comparison, does not recieve the independent variable
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conclusion
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A judgement based on the information obtained
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Theroy
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An explanation supported by many experiments; is still subject to new experimental data, can be modified and is considered valid if it can be used to make predictions that are proven true
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qualitative data
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information concerning the 5 senses, color, odor, shape or other physical characteristics
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quantitative data
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numerical information describing how much, how little, how big, how tall or how fast.
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chemistry
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the study of matter and the changes it undergoes.
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matter
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anything that has mass and takes up space (everything)
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mass
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a measure that reflects the amount of matter
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weight
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a measure of an amount of matter and also the effect of Earth;s gravitational pull on that matter
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unit
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observation
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gathering data, 2 types quantatitve and qualatitive
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derived unit
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a unit defined by a combination of base units.
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density
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the amount of mass per unit volume; a physcial property
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meter
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the SI base unit for length
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Kelvin
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The SI base unit of tempature
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Kilogram
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The SI base unit for mass
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element
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A pure substance that cannot be broken down into simpilar substacnes by physcial or chemical means.
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periodic table
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a chart that organzies all known elements into a grid of horizontal rows (periods) and all vertical columns (groups or families) arranged by increasing atomic number
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compunds
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a chemical combination that consists of two or more different elements; CAN be broken down into simplier substances by chemical means and has properties different from those of its component elements.
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Chemcial names
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chemical symbols
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metals
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an element that is solid at room tempature, a goof conductor of heat and electrictiy, and gennerally is shiny; most metals are ductile and malleable.
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non-metals
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elements that are generally gases or dull, brittle solids that are poor conductors of the particles involved
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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 seperated by physical means.
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homogeneous mixtures
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one that has a uniform compostion throughout and always has a single phase; also called a solution
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heterogeneous mixtures
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one that does NOT have a uniform compostion and in which the individual substances remain distinct. (trail mix) easy to seperate.
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Solution
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a uniform mixture that can contain solids, liquids, or gases; also called a homogeneous mixture
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filtration
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a technique that uses a porous barrier to seperate a solid from a liquid
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distillation
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a technique that can be used to physcially seperate most homogeneous mixtures based on the differences in the boiling points of the substances.
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chromatography
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a technique that is used to seperate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material.
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physical properties
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a charateristic of matter that can be observed or measured without changing the sample's compostion-for example density, color, taste, hardness, and melting point.
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physcial change
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a type of chnage that alters the physcial properties of a substance but does not change its compostion
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chemcial change
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a process involving one or more substances changing into new substances; also called a chemical reaction
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chemcial property
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the ability or inability of a substacnce to combine with or chnage into one of more new substances.
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phase chnage
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a transition of matter from one state to another
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chemical change
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a process involving one or more substances changing into new substances; also called a chemical reaction.
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evidence of chemical reaction
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gas, color, bubbles, precipitate
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reactant
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the starting substance in a chemcial reaction
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product
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a substacne formed during a chemcial reaction
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law of conservation of mass
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matter is neither created nor destroyed
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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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accuracy
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refers to how close a measured value is to an accepted value
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precision
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refers to how close a seris of measurements are to one another; precise measurments show little variation over a seris of trials but might not be accurate
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error
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the difference between an experimental value and an accepted value
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percent error
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the ratio of an error to an accepted value
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scientfic notation
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expresses any number as a number between 1 and 10 (known as coefficent) multiplied by 10 rasied to a power (known as exponent)
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scientfic figures
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the number of all known digits reported in measurments plus one estimated digit
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powers of ten
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rounding numbers
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Atom
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The smallest particle of an element that retains all the properties of that element; is electrically neutral, spherically shaped, and composed of electrons, protons and neutrons
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electron
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a negativley charged, fast moving paticle with an extremely small mass that is found in all forms of matter and moces through the empty space surrondings an atom's nucleus
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Proton
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a subatomic particle in an atoms nucleus that has a positive charge of 1+.
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neutron
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A neutral, subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton
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atomic number
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the number of protons in an atom
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atomic mass
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the weighted average mass of the isotopes of that element
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isotopes
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atoms of the same element with different numbers of neutrons
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mass number
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the number after an elemenet's name, representing the sum of its protons and neutrons
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nucleus
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the extremley small, positively charged, dense center of an atom that contains positively charged protons and neutral atoms
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electromagnetic radiation
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A form of energy exhibiting wavelike behavior as it travels through space; can be described by wavelength, frequency, amplitude, and speed
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wavelength
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the shortest distance between equivalent points ona continuous wave; is ussual;y expressed in meters, centimeters, or nanometers
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frequency
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the number of waves that pass a given point per second
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amplitude
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the height of a wave from the origin to crest, or from the origin to the trough
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atomic emission spectrum
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a set of frequencies of electromagnatic waves given off by atoms of an element; consists of a seris of fine lines of individual colors
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ground state
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the lowest allowable energy state of an atom
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quantum number
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the number assigned to each orbit of an electron
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quantum mechanical model of an atom
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an atomic model in whihc electrons are treated as waves; also called the wave mechanical model of the atom
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atomic orbital
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a 3-d region around the nucleus of an atom that describes an electron's probable location
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energy sublevels
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the energy levels contained witiin a principal energy level
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elctron configurations
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the arrangment of electrons in an atom, which is prescribed by three rules- the aufbau principle, the pauli exclusion, and Hund's rule
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valence elctrons
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the atoms in the farthest electron shell, determine the chemcial properties in an atom
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group
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A vertical column of elements in the periodic table arranged in order of increasing atomic number; also called family 1-18
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periods
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a horizontal row of elements in the modern periodic table (1-9)
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periodic law
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states that when the elements are arranged by increasing atomic number, there is a periodic repetition of their propeties
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representative elements
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elements from groups 1,2 and 13-18 in the modern periodic table, possesing a wide range of chemical and physcial properties
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transition elements
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elements in groups 1-12 fof the mdoern perodic table and are furhter divded into transition metals and inner transition elements
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alkaline
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group 2 elements in the modern periodic table and are highly reactive
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Halogens
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A highly reactive group 17 element
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Noble gases
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an extremley unreactive group 18 element
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Periodic trends
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Ionic compounds
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compounds that contain ionic bonds
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salts
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an ionic compond made up of a cation from a base and an anion from an acid
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ionic cmopunds and physcial state
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ionic cmopunds and conducting electrcity
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covalent compunds
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a chemical compound that resukts from the sharing of valence electrons
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bonding
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VSEPR model
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valence shell electron pair repulsion model, which is based on an arragment that minimizes the repulsion of shared and unshared pairs of electrons around the central atom
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dot structures
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putting dots that resemble electrons around the abbrievation of the element
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nomenclature
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naming of things in science
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ions
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an atom or bonded group of atoms with a positive or negative charge
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polyatomic ions
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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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metals and drifting electrons
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diatmoic molecules
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molecules composed of only two atoms
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skeleton equations
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use symbols and formulas to represent the reactants and products, but they do not state how many atoms are involved in the reaction
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chemcial equations
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a statement using chemcial formulas to describe the identies and relative amounts of the reactants and products involved in the chemical equations
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coefficients
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in a chemcial equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all reactants and products
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Synthesis
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reaction in which two or more substances react to produce a single product
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Combustion
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oxygen combines with a substance and releases energy in the form of heat and light
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decompistion
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reaction in which a ginle compound breaks down into two or more elemetns or new compounds
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single replacment
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a reation in which the atoms of one element replace the atoms of another element in a compound
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double replacment
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reaction in which ions exchange between two compounds
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aq
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disolves in water
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l
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liquid
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s
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solid
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g
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gaeous
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arrow
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seperates reactants from products
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two reverse arrows
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the eqaution is reversable
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+
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sperates 2 or more products or reactants
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complete/ionic equations
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an ionic equation that shows all the particles in a solution as they realistically exist
