Base your answer(s) to the following question(s) on the
information below.
A student was studying the pH differences in samples from
two Adirondack streams. The student measured a pH of 4
in stream A and a pH of 6 in stream B.
Compare the hydronium ion concentration in stream A to the
hydronium ion concentration in stream B.

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.