The substances that interact during a chemical reaction are called reactants. They are the starting materials of the reaction.

Here's a simple example:

* Reactants: Hydrogen gas (H₂) and Oxygen gas (O₂)

* Reaction: Burning (combustion)

* Product: Water (H₂O)

Here's a more detailed breakdown:

* Reactants: These are the substances that are present at the beginning of the reaction. They are the ingredients that will be transformed into something new.

* Chemical Reaction: This is the process where the reactants undergo a chemical change, rearranging their atoms and forming new bonds.

* Products: These are the substances that are formed as a result of the chemical reaction. They are the new compounds that are created from the rearrangement of the reactants.

It's important to remember that during a chemical reaction, the atoms are not created or destroyed, they are simply rearranged. This is the fundamental principle of the Law of Conservation of Mass.