Final answer:
Energy is released when monomers are joined to form a polymer through dehydration synthesis, where water is also produced as a byproduct of this reaction.
Step-by-step explanation:
When individual monomer units are joined together to form a polymer, energy is released. This process, known as dehydration synthesis, involves monomers combining and releasing water molecules as byproducts, where one monomer contributes a hydrogen atom (H) and the other a hydroxyl group (OH). The reaction results in the formation of covalent bonds between the monomers, creating a larger molecule or polymer.