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activation energy

noun, Chemistry
the least amount of energy required to activate atoms or molecules to a state in which they can undergo a chemical reaction.
Origin of activation energy
1920-25 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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activation-energy in Science
activation energy
The least amount of energy needed for a chemical reaction to take place. Some elements and compounds react together naturally just by being close to each other, and their activation energy is zero. Others will react together only after a certain amount of energy is added to them. Striking a match on the side of a matchbox, for example, provides the activation energy (in the form of heat produced by friction) necessary for the chemicals in the match to ignite. Activation energy is usually expressed in terms of joules per mole of reactants.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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