What is common to both hydrochloric acid and trioxonitrateVacid? A. Both are monobasic
B. Both attack rubber
C. Both are used to prepare hydrogen from zinc granules
D. Both are used for fountain experiment

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.