Which change will decrease the number of effective collisions during a chemical reaction? [a] adding a catalyst[b] increasing the surface area[c] decreasing the temperature[d] increasing the reactant concentrations[e] increasing the volume of the reactants

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.