Final answer:
A model is a representation used to visualize and analyze phenomena that cannot be directly observed, whereas a theory is a scientifically supported explanation for patterns in nature.
Step-by-step explanation:
When something cannot be directly observed, it can be represented by a model. A model is a conceptual or computational representation used to visualize and analyze phenomena that are difficult or impossible to observe directly. For example, the planetary model of the atom helps us understand atomic spectra, even though we can't observe electron orbits with our senses. Conversely, a theory is an explanation for patterns in nature that is supported by strong scientific evidence and repeatedly verified by various researchers. In contrast, a hypothesis is a tentative explanation for a set of observations that can be tested through experiments or further observations.