Question: What represents the control group in the following
experiment? A scientist tests
whether flies live longer in hot
temperatures. She places 100 flies
in an unheated room, 100 flies in a
heated room, and 100 files in a
super-heated room.

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.