Meaning & use
reactant
Last updated
Meaning
nouncountablechemistry
A substance that is consumed or changed when a chemical reaction happens.
Grammar: Has a plural reactants; appears on the left side of a chemical equation before the arrow.
Patterns
- reactants and products
- limiting reactant
- reactant concentration
- a reactant in a reaction
In the equation, hydrogen and oxygen are the reactants.
The limiting reactant runs out first and stops the reaction.
Students measured how reactant concentration changed the reaction rate.
Word forms
| plural | reactants |
|---|
Common combinations
- limiting reactant
- Find the limiting reactant before predicting the product mass.
- reactant concentration
- Higher reactant concentration often speeds up the reaction.
- reactants and products
- Label the reactants and products in the chemical equation.
Synonyms and how they differ
- reagent
- A substance used to test for or trigger a reaction; it may not be consumed.
- starting material
- Plain wording for what enters a reaction, common in labs and industry.
- substrate
- In enzyme reactions, the specific molecule an enzyme acts on; narrower than reactant.
Opposites
Word family
Commonly confused: reactant or catalyst? reactant or product?
reactant vs catalyst
A catalyst speeds a reaction but is not consumed; a reactant is used up.
reactant vs product
Products are made by the reaction; reactants are present before it.
Practice
In a chemical equation, reactants are usually written where?
Choose one answer.
Reactants are the starting substances, placed left of the arrow; products appear on the right. A catalyst may be written nearby but is not a reactant.
Make it your own
Write a sentence using “reactant”, then check it and compare it with the examples above.