Which term best describes a substance or molecule that participates in a chemical reaction?

• A. Reactant
• B. Solvent
• C. Catalyst
• D. Product

Answer: (A)

Verified step by step guidance

1. Understand the context of the question: it asks for the term that describes a substance or molecule that participates in a chemical reaction.
2. Recall the definitions of the terms given: a Reactant is a substance that undergoes change during a chemical reaction; a Solvent is a medium in which reactions may occur but does not necessarily participate chemically; a Catalyst speeds up a reaction without being consumed; a Product is the substance formed as a result of the reaction.
3. Identify that the term describing a substance that actively participates and changes during the reaction is 'Reactant'.
4. Recognize that Solvent, Catalyst, and Product do not fit the description of a substance that participates by undergoing change in the reaction.
5. Conclude that the best term to describe a substance or molecule that participates in a chemical reaction is 'Reactant'.