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College Chem


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Nuclear Fission
the splitting of a large nucleus such as U-235 into smaller ones with the release of energy
Chain reaction
a reaction that becomes self-sustaining. For example nuclear fission become a chain reaction under certain conditions
Critical mass
the amount of fissionable fuel required to sustain a chain reaction
Primary coolant
a liquid that come in direct contact with a nuclear reactor to carry away heat
a material that slows the speed of the neutrons in nuclear reactor making them more effective in causing fission
Secondary coolant
the water in steam generator that does not come in contact with the reactor
Enriched uranium
uranium that has a higher percent of U-235 than .7% the natural abundance
Gaseous diffusion
a process in which a gas is forced through a series of permeable membranes to separate molecule of different masses
Depleted uranium (DU)
uranium (U-238) that has been depleted of the small amount of U-235 that it once naturally contained
for a particular radioisotope the time required for the level of radioactivity to fall to one-half of its value
High-level radioactive waste (HLW)
nuclear waste with high levels of radioactivity. HLW requires essentially permanent isolation form the biosphere because of the long half-lives of the radioisotopes involved. It consists of the radioactive materials that result from the reprocessing of spent nuclear fuel
Low-level radioactive waste (LLW)
waste such as clothing, shoes, filters, or medical equipment that is contaminated with smaller quantities of radioactive material than HLW contains. This category specifically excludes spent nuclear fuel
Spent nuclear Fuel (SNF)
the radioactive material remaining in fuel rods after they have been used to generate power in a nuclear reactor
Breeder reactor
a type of nuclear reactor that created new fissionable fuels (e.g., Pu-239) while the current fissionable fuel of the reactor (U-235) undergoes fission
the spontaneous emission of radiation by certain radioisotopes, such as C-14 or I-131
Alpha particle
(α) a positively charged (+2) particle that consist of the nucleus of helium atom-two protons and two neutrons
Beta particle
(β) a high speed electron emitted from a nucleus
Gamma ray
(γ) high energy, short wavelength photons that may be emitted form the nucleus during the process during the process of nuclear decay
a radioactive isotope of an element
Radioactive decay series
a characteristic pathway of radioactive decay that begins with a heavier isotope such as U-238 and ends with a stable isotope such as Pb-206
Background radiation
the average daily amount of radiation to which we each are exposed. The amount of background radiation depends on location
Curie (Ci)
a measure of radioactivity equivalent to the number of decays per second from one gram of radium
Rad(radiation absorbed dose)
a unit of radiation that indicated the absorption of 0.01 J of radiant energy per kilogram of tissue
Rem (roentgen equivalent man)
a unit of equivalent dose that indicated the damage done by a particular dose of radiation. A rem is the number of rads multiplied by the quality factor Q
Sievert (Sv)
a unit of equivalent dose equal to 100 rem
Greenhouse Gases
gases that are capable of absorbing and reemitting infrared radiation to the atmosphere
Greenhouse effect
the process by which atmospheric gases trap and return a major portion of the heat (infrared radiation) radiated by the earth
Enhanced greenhouse effect
often used to refer to an energy return of greater than 81%
only certain energy levels are permitted; a noncontinuous energy distribution that consist of many individual, or discrete, steps
Atomic mass (atomic weight)
the mass of an atom expressed relative to a value of exactly 12 for an atom of C-12
Avogadro’s number
the number of atoms in exactly 12g of C-12 (6.02 X 10^23); also the number of particle per mole of substance such as covalently bonded molecule
Avogadro’s number of particles being specified
Molar mass (molecular weight)
the mass of one mole, or Avogadro’s number, of whatever particles are being specified
Anaerobic bacteria
bacteria that thrive without the use of molecular oxygen
Global warming potential(GWP)
a number that represents the relative contribution of a molecule of the indicated substance to global warming
the form of energy describing movement against a restraining force; equal to the force multiplied by the distance over which the motion occurs
Capacity to do work
the energy that flows for m hotter to a colder object
the property that determined the direction of heat flow
Calorie (kcal) calorie (cal)
the unity used in nutrition 1 cal = 1 kcal = 4.184 kJ
First law of thermodynamics
the principle that energy is neither created nor destroyed in a chemical reaction; also called the law of conservation of energy
Potential energy
the form of energy related to the position of atoms and molecular structure and stored in chemical bonds
Kinetic energy
the energy of motion
Thermal energy
the random motion of molecules
Second law of thermodynamics
the principle that states that it is impossible to completely convert heat into work without making some other changes in the universe
randomness or disorder in position or energy
rapid combination of oxygen with a substance (e. g. fuel) to form products
describes any chemical or physical change that releases heat
describes any chemical or physical change that absorbs heat
Heat of combustion
the quantity of heat energy given off when a specified amount of substance burns in oxygen
Bond energy
amount of energy that must be absorbed to break a specific chemical bond
Activation energy
the energy necessary to initiate a reaction
compound of hydrogen and carbon
a hydrocarbon with only single bonds between carbons
a purification or separation process in which a solution is heated to it’s boiling point and the vapors are condensed and collected
chemical process by which large molecules are broken into smaller ones suitable to be used in gasoline.
Catalytic cracking
a process by which catalysts are used to promote molecular breakdown at lower temperatures than those used in thermal cracking
Thermal cracking
the heating of starting material to a high temperature
molecules with the same chemical formula ( same number and kinds of atoms) but different molecular structures and properties
Oxygenated gasoline
blends of petroleum-derived hydrocarbon with oxygen-containing compounds such as MTBE, ethanol, or methanol
Reformulated gasoline (RGFs)
an oxygenated gasoline that contains a lower percentage of certain more volatile hydrocarbons such as benzene found in conventional gasoline
material produced by biological processes
A physical combination of two or more substances that may be present in variable amounts,substances retain their identity,may be separated by ordinary physical means
Pure substance
matter consisting of only one identifiable substance,cannot be separated by ordinary physical means – you have to change the identity of the substance to break it down further (chemical means)
pure substance that cannot be broken down into simpler ones by any chemical means (carbon, gold, copper, oxygen, nitrogen, silicon)
pure substance made up of two or more elements in a fixed, characteristic chemical combination (water, carbon dioxide, calcium carbonate)
Pure substances
are distinguished from one another by their properties
Physical properties
can be determined without changing the identity of the substance (color, phase at 25oC, density)
Chemical properties
have to be determined by changing the identity of the substance (i. e. by chemical means: e. g. how elements combine to form compounds or whether a substance burns in air or not)
smallest unit of an element that can exist as a stable, independent entity
two or more elements in fixed chemical combination
Chemical Formulas
Symbolic way to represent the elementary composition of a pure substance
Diatomic Elements
is a molecule composed of two atoms is the elementary particle,H2, N2, O2, F2, Cl2, Br2, I2
readily vaporized (passes into the vapor phase)
chemical substance that influences the speed of a chemical reaction without being changed itself
Risk assessment
Evaluation of scientific data and making predictions in an organized manner about the probabilities of occurrence
two or more forms of the same element that differ in their properties due to differences in molecular structure or crystal structure

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