What is the difference between an incendiary fire and an accidental fire

An incendiary fire is when a fire is intentionally started knowing it shouldn't be. And an accidental fire is when a fire is started accidentally or without purposeful intent.

h let me think

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.