chemistry midterm exam study guide

Scientific method
a systematic approach used in scientfic study; an organizd process used by scientists to do research and verify the work of others

Hypothesis
A tentative, etstable statement or prediction about what has been observed

experiment
A set of controlled observations that test a hypothesis

Control
in an experiment, the standard that is used for comparison, does not recieve the independent variable

conclusion
A judgement based on the information obtained

Theroy
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

qualitative data
information concerning the 5 senses, color, odor, shape or other physical characteristics

quantitative data
numerical information describing how much, how little, how big, how tall or how fast.

chemistry
the study of matter and the changes it undergoes.

matter
anything that has mass and takes up space (everything)

mass
a measure that reflects the amount of matter

weight
a measure of an amount of matter and also the effect of Earth;s gravitational pull on that matter

unit

observation
gathering data, 2 types quantatitve and qualatitive

derived unit
a unit defined by a combination of base units.

density
the amount of mass per unit volume; a physcial property

meter
the SI base unit for length

Kelvin
The SI base unit of tempature

Kilogram
The SI base unit for mass

element
A pure substance that cannot be broken down into simpilar substacnes by physcial or chemical means.

periodic table
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

compunds
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.

Chemcial names

chemical symbols

metals
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.

non-metals
elements that are generally gases or dull, brittle solids that are poor conductors of the particles involved

mixture
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.

homogeneous mixtures
one that has a uniform compostion throughout and always has a single phase; also called a solution

heterogeneous mixtures
one that does NOT have a uniform compostion and in which the individual substances remain distinct. (trail mix) easy to seperate.

Solution
a uniform mixture that can contain solids, liquids, or gases; also called a homogeneous mixture

filtration
a technique that uses a porous barrier to seperate a solid from a liquid

distillation
a technique that can be used to physcially seperate most homogeneous mixtures based on the differences in the boiling points of the substances.

chromatography
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.

physical properties
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.

physcial change
a type of chnage that alters the physcial properties of a substance but does not change its compostion

chemcial change
a process involving one or more substances changing into new substances; also called a chemical reaction

chemcial property
the ability or inability of a substacnce to combine with or chnage into one of more new substances.

phase chnage
a transition of matter from one state to another

chemical change
a process involving one or more substances changing into new substances; also called a chemical reaction.

evidence of chemical reaction
gas, color, bubbles, precipitate

reactant
the starting substance in a chemcial reaction

product
a substacne formed during a chemcial reaction

law of conservation of mass
matter is neither created nor destroyed

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

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

precision
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

error
the difference between an experimental value and an accepted value

percent error
the ratio of an error to an accepted value

scientfic notation
expresses any number as a number between 1 and 10 (known as coefficent) multiplied by 10 rasied to a power (known as exponent)

scientfic figures
the number of all known digits reported in measurments plus one estimated digit

powers of ten

rounding numbers

Atom
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

electron
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

Proton
a subatomic particle in an atoms nucleus that has a positive charge of 1+.

neutron
A neutral, subatomic particle in an atom’s nucleus that has a mass nearly equal to that of a proton

atomic number
the number of protons in an atom

atomic mass
the weighted average mass of the isotopes of that element

isotopes
atoms of the same element with different numbers of neutrons

mass number
the number after an elemenet’s name, representing the sum of its protons and neutrons

nucleus
the extremley small, positively charged, dense center of an atom that contains positively charged protons and neutral atoms

electromagnetic radiation
A form of energy exhibiting wavelike behavior as it travels through space; can be described by wavelength, frequency, amplitude, and speed

wavelength
the shortest distance between equivalent points ona continuous wave; is ussual;y expressed in meters, centimeters, or nanometers

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

amplitude
the height of a wave from the origin to crest, or from the origin to the trough

atomic emission spectrum
a set of frequencies of electromagnatic waves given off by atoms of an element; consists of a seris of fine lines of individual colors

ground state
the lowest allowable energy state of an atom

quantum number
the number assigned to each orbit of an electron

quantum mechanical model of an atom
an atomic model in whihc electrons are treated as waves; also called the wave mechanical model of the atom

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

energy sublevels
the energy levels contained witiin a principal energy level

elctron configurations
the arrangment of electrons in an atom, which is prescribed by three rules- the aufbau principle, the pauli exclusion, and Hund’s rule

valence elctrons
the atoms in the farthest electron shell, determine the chemcial properties in an atom

group
A vertical column of elements in the periodic table arranged in order of increasing atomic number; also called family 1-18

periods
a horizontal row of elements in the modern periodic table (1-9)

periodic law
states that when the elements are arranged by increasing atomic number, there is a periodic repetition of their propeties

representative elements
elements from groups 1,2 and 13-18 in the modern periodic table, possesing a wide range of chemical and physcial properties

transition elements
elements in groups 1-12 fof the mdoern perodic table and are furhter divded into transition metals and inner transition elements

alkaline
group 2 elements in the modern periodic table and are highly reactive

Halogens
A highly reactive group 17 element

Noble gases
an extremley unreactive group 18 element

Periodic trends

Ionic compounds
compounds that contain ionic bonds

salts
an ionic compond made up of a cation from a base and an anion from an acid

ionic cmopunds and physcial state

ionic cmopunds and conducting electrcity

covalent compunds
a chemical compound that resukts from the sharing of valence electrons

bonding

VSEPR model
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

dot structures
putting dots that resemble electrons around the abbrievation of the element

nomenclature
naming of things in science

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

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

metals and drifting electrons

diatmoic molecules
molecules composed of only two atoms

skeleton equations
use symbols and formulas to represent the reactants and products, but they do not state how many atoms are involved in the reaction

chemcial equations
a statement using chemcial formulas to describe the identies and relative amounts of the reactants and products involved in the chemical equations

coefficients
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

Synthesis
reaction in which two or more substances react to produce a single product

Combustion
oxygen combines with a substance and releases energy in the form of heat and light

decompistion
reaction in which a ginle compound breaks down into two or more elemetns or new compounds

single replacment
a reation in which the atoms of one element replace the atoms of another element in a compound

double replacment
reaction in which ions exchange between two compounds

aq
disolves in water

l
liquid

s
solid

g
gaeous

arrow
seperates reactants from products

two reverse arrows
the eqaution is reversable

+
sperates 2 or more products or reactants

complete/ionic equations
an ionic equation that shows all the particles in a solution as they realistically exist

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