7. Volume-Mass Problem: Ammonia and gaseous hydrogen chloride combine to form ammonium chloride:
NH3(g) + HCI (g)—->
NH4Cl (s)
What mass of Ammonium Chloride at 25.0 degrees Celcius and 760. Torr will form if you combine 4.21 L
of Ammonia with hydrogen chloride?
enibson

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.