1. matter is
2. atoms are
an example of an atom is
3. molecules are
an example of a molecule is

Matter is anything that mass and can occupy space.

Atoms are the smallest particles that takes part in a chemical reaction.

A molecule is a that can exist on its own

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.