chemistry vocab midterm

analytical chemistry

the study of the composition of substances

biochemistry

the study of the composition and behavior of substances in living organisms

chemistry

the study of the structure, properties, and composition of substances and the changes that substances undergo

experiment

a carefully controlled, repeatable procedure for gathering data to test a hypothesis

hypothesis

a proposed explanation for observation

inorganic chemistry

primarily the study of substances that do not contain carbon

organic chemistry

the study of compounds that contain the element carbon

observation

information obtained through the sense which often involves measurements

physical chemistry

the study of theoretical basis of chemical behavior, relying on mathematics and physics

scientific law

a concise statement that summarizes the results of many observations and experiements

scientific method

a method of inquiry involving observation, experiments, hypothesis, and broad explanations called theories

theory

a thoroughly tested model that explains why experiments give certain results

chemical property

the ability of a substance to undergo chemical reactions and to form new substances

chemical reaction

the changing of substances to other substances by the breaking of bonds in reactants and the formation of bonds in products

chemical symbol

a one or two letter representation of an element

compound

a substance that can be separated into simpler substances only by chemical reactions

distillation

a purification in which a liquid is evaporated and then condensed again to a liquid; used to separate dissolved solids from liquids or liquids from liquids according to boiling points

element

a substance that cannot be changed into simpler substance under normal laboratory conditions

gas

matter that has no definite shape or volume; it adopts the shape and volume of its container

heterogeneous mixture

a mixture that in not uniform in composition

homogeneous mixture

a mixture that is completely uniform in composition

law of conservation of mass

mass can neither be created nor destroyed in an ordinary chemical or physical process

liquid

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

mass

the amount of matter that an object contains which is measured in kilograms

matter

anything that has mass and takes up space

mixture

a physical blend

phase

any part of a system with uniform composition and position

physical change

an alternation of a substance that does not affect its chemical composition

physical property

a quality of substance that can be observed or measured without changing the substance’s chemical composition

product

a substance formed in a chemical reaction

reacant

that starting substance in a chemical reaction

solid

matter that has definite shape and volume

solution

another name for a homogeneous solution

substance

a sample of matter having a uniform and definite composition; it can be either an element or a compoun

vapor

a substance in the gaseous state that is ordinarily a liquid or solid at room temperature

absolute zero

the zero point on the Kelvin temperature scale; equivalent to -273.15 C; all molecular motion theoretically stops at this temperature

accepted value

a quantity used by general agreement of the scientific community

accuracy

the closeness of a measurement to the true value of what is being measured

celcius scale

the temperature scale on which the freezing point of water is 0 C and the boiling point is 100 C

density

the ratio of the mass of an object to its volume

error

the difference between the accepted value and the experimental value

experimental value

a quantitative value measured during an experiment

gram

a metric mass unit equal to the mass of 1 cm3 of water at 4 C

hydrometer

a device used to measure the specific gravity of a liquid

international system of units

a revised version of the metric system, adopted by international agreement in 1960

kelvin scale

the temperature scale in which the freezing point of water is 273 K and the boiling point is 373 K

kilogram

the mass of 1 liter of water at 4 C; it is the base unit of mass in SI

liter

the volume of a cube measuring 10 cm on each edge (1000cm)

meter

the base unit of length in SI

percent error

the percent that a measured value differs from the accepted value

precision

describes the closeness, or reproducibility, of a set of measurements taken under the same conditions

qualitative measurement

a measurement that gives descriptive, nonnumerical results

quantitative measurment

a measurement that gives definite, usually numeric results

scientific notation

expression of numbers in the form n x 10n where n is equal to or greater than 1 and less than 10 and n is an integer

scientific figure

all the digits that can be known precisely in a measurement, plus a last estimated digit

specific gravity

the ratio of the density of a substance to that of a standard substance (water)

temperature

a measurement of the average kinetic energy of particles in matter

volume

the space occupied by a sample of matter

weight

force that measures the pull of gravity on a given mass

conversion factor

a ratio of equivalent measurements used to convert a quantity from one unit to another

dimensional analysis

a technique of problem-solving that uses the units that are part of a measurement to help solve the problem

alkali metals

group 1A soft, silvery, colored metals; very reactive

alkaline earth metal

any metal in Group 2A of the periodic table

atom

the smallest particle of an element that retains the properties of that element

atomic mass

the weighted average of the masses of the isotopes of an element

atomic mass unit

a unit of mass equal to one-twelfth the mass of a carbon-12 atom

atomic number

the number of protons in the nucleus of an of an element

cathode ray

a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure

dalton’s atomic theory

the first theory to relate chemical changes to events at the atomic level

group

a vertical column of elements in the periodic table

halogen

any member of the nonmetallic elements in group 7A of the periodic law

inner transition metal

an element in the lanthanide and actinide series

isotope

atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons

mass number

the total number of protons and neutrons in the nucleus of an atom

metal

one of a class of elements that includes a large majority of the known elements which are characteristically lustrous, malleable, ductile, and good conductors of heat and electricity

metalloid

one class of elements having properties intermediate to metal nonmetals

nonmetal

one of a class of elements that are not lustrous and generally poor conductors of heat and electricity

proton

a positively charged subatomic particle found in the nucleus of an atom

nuetron

a subatomic particle with no charge and a mass of 1amu found in the nucleus of the atom

electron

a negatively charged subatomic particle

noble gas

any member of a group of gaseous elements in Group O of the periodic table

period

a horizontal row of elements in the periodic table

periodic law

an arrangement of elements into rows and columns according to similarities in their properties

representative elements

group A elements on the periodic table which have only partially filled outermost “s” and “p” sublevels

transitions metals

group B elements characterized by addition of electrons to “d” suborbitals

alpha particle

a positively charged particle emitted from certain radioactive nuclei; it consists of two protons two neutron and is identical to the nucleus of helium atom

alpha radiation

alpha particles emitted from a radioactive source

band of stability

the location of stable nuclei on a neutron-vs-proton plot

beta particle

a fast-moving electron emitted from certain radioactive nuclei

beta radiation

fast-moving electrons (beta particles) emitted from a radioactive source

film badge

a small radiation detector worn by persons who work near radiation sources

fission

the splitting of a nucleus into smaller fragments; accompanied by the release of neutrons and a large amount of energy

fusion

a reaction in which two light nuclei combine to produce a nucleus of heavier mass, accompanied by the release of a large amount of energy

gamma radiation

high energy electromagnetic radiation emitted by certain radioactive nuclei which have no mass or electrical charge

geiger counter

a gas-filled metal tube used to detect the presence of beta radiation

half-life

the time required for one-half of the atoms of radioisotope to emit radiation and decay to products

ionizing radiation

radiation with enough energy to produce ions by knocking electrons off some atoms of a bombarded substance

neutron absorption

a process used in a nuclear reactor to slow the chain reaction by decreasing the number of moving neutrons

neutron moderation

a process used in a nuclear reactor to slow the neutrons so they can be captured by the reactor fuel to continue the chain reaction

positron

a particle that has the same mass as an electron but that has a positive charge