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Teacher professional development and classroom resources across the curriculum

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Unit 12: Kinetics and Nuclear Chemistry—Rates of Reaction


Activated complex
A chemical species midway between reactant molecules and product molecules.
Activation energy
The amount of energy that the reactants need to reach the activated complex.
A substance made of antiparticles, such as positrons and antiprotons, which have the same mass but opposite charge as their matter counterparts. When a particle and its antiparticle collide, both are annihilated and energy is released.
Beta particles
A high-energy electron produced in the process of nuclear decay (β-).
Binding energy
The energy released when a nucleus is broken into individual protons and neutrons.
A substance that speeds up a chemical reaction, yet remains unchanged by the chemical reaction.
Chain reaction
A reaction in which the products cause further reactions to take place.
Chemical kinetics
The study of the rates of chemical reactions.
Critical mass
The minimum amount of a substance needed to sustain a fission chain reaction.
Electron capture
A type of nuclear decay in which a nucleus captures an electron from a low energy level.
Elementary steps
A sequence of simple chemical reactions that make up the mechanism of an overall reaction.
A biological catalyst.
The splitting of an atomic nucleus into smaller particles.
The combining of smaller atomic nuclei to make a larger nucleus.
Gamma emission
A type of nuclear decay in which a rearrangement of nuclear particles releases a gamma ray.
Gamma radiation
High-energy electromagnetic radiation.
Half-life (radioactive)
The time needed for half of a radioactive substance to decay.
Half-life (kinetic)
The time required for a reaction to proceed halfway to the products.
A chemical species produced by an elementary step of a chemical reaction, and then consumed by another. Intermediates do not appear in the overall chemical equation.
Mass defect
The mass lost by nuclear particles when they come together to form a nucleus.
Net equation
A chemical equation for a reaction that lists only the reactants and products participating in the reaction.
An antimatter particle equal in mass to the electron but with a positive charge.
Positron emission
A type of nuclear decay that releases a positron.
Potential energy diagram
A graph that shows the potential energies of reactants, the activated complex, and the products as the reaction progresses. It is also called a reaction coordinate diagram.
Radiocarbon dating
A method of determining the age of ancient artifacts by measuring the amounts of different carbon isotopes in the artifact.
Rate constant
A multiplicative factor in a reaction's rate law that is related to the approximate rate of the reaction.
Rate law
An equation that shows how the rate of a reaction depends on the concentration of the reactants.
Rate-determining step
The slowest elementary step in a reaction mechanism.
Reaction order
The exponent of a reactant's concentration in a rate law.
Strong force
The nuclear force between protons and neutrons that holds a nucleus together.
Subcritical mass
An amount of a fissile material below the critical mass.
Supercritical mass
An amount of a fissile material above the critical mass.
The second-highest energy form of electromagnetic radiation, exceeded by gamma rays.

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