"Fuel". We have avoided the words "fuel" and "waste" although they are often used to describe the substrate and product of coupled reactions (e.g., MeI and MeOH), leading to expressions such as "chemically fueled self-assembly" and "chemical fuel driven motor". However, "fuel" is extremely evocative, recalling macroscopic engines, and thus leads ineluctably to related images of a "fuel" molecule providing a "kick" that, in the case of motors, drives mechanical motion. This analogy is mechanistically incorrect; if one molecule undergoes a spontaneous reaction with another, they remain at thermal equilibrium with their environment -bonds are not "excited", and molecules are not "pushed". Indeed, because molecules exist in a low Reynold's number regime, momentum is a meaningless concept in the discussion of molecular motors. Related to this is a tendency to suggest that some fraction of the free energy associated with a "high energy fuel" can be used to do work against an opposing force in molecular motors. However, Hill demonstrated that it is not possible or meaningful to attempt to identify in which step of the reaction cycle chemical potential is transduced into mechanical energy in the operation of a molecular motor. Similarly, in the context of supramolecular materials, it is often suggested that the reaction between the "fuel" and a non-self-assembling monomer unit (e.g., 14, Figure ) produces an "activated" monomer ( ) that then self-assembles. This process is sometimes drawn as energetically uphill to signify "activation", despite spontaneous chemical reactions being exergonic. This is connected to the idea of some proportion of the energy associated with a "high energy fuel" being stored in the self-assembled structure. These misunderstandings perhaps stem from the language that biochemists and biologists use when discussing and thinking about bond breaking and making energetics; 45 it is sometimes said that "high-energy phosphate" is produced during ATP hydrolysis or that the breaking of a "high energy phosphate bond" in ATP is used to "fuel" biological processes. Chemists should recognize the fallacy of such claims.