To demonstrate, consider the following two molecules. To answer the question, you have to rotate one or both of the images in your head. Both images do represent the same molecule, only the viewing angle is different. A model makes this kind of question much easier to answer. You just spin the model around in your hand until it matches the illustration, or until you convince yourself that it cannot match the illustration.
Computer models are an alternative to physical models.
For certain tasks, they may not be as satisfying as a model that you can hold in your hand. But a computer model that you can manipulate on-screen is definitely better than a static illustration. Here are two more molecules. Once again, try to determine if they represent different molecular species or if they are just the same molecule viewed from different angles. Back to the main molecular models page.