If a piece of metal were to cut in half would the density change

No, the density is the same even if it's cut in half or how ever many pieces.

so the metal would be the same.

Thanks,

Deku ❤

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.