Any process in which reactants are changed into products by the breaking or creation of chemical bonds(noun)
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Use "chemical change" in a sentence
"In the early 1960s, Eric J. Simon, at the New York University Medical Center, had been impressed by the fact that pharmaceutical companies can manufacture a substance that acts like morphine but, through a slight chemical change in the compound, can be converted into an “opiate antagonist,” a substance that blocks the action of morphine."