What is the mole ratio of silicon tetrachloride to carbon dioxide when carbon tetrachloride combusts in the
presence of oxygen gas and hydrogen gas to form
carbon dioxide and hydrogen chloride?

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.

let that person have a turn to speak : )