If the reaction producing nickel is as follows: ni(co)4(g) + heat ni(s) + 4co(g) - heat the reaction from left to right is and, therefore, the addition of heat will the production of nickel.

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.