1. Para calcular la densidad de un trozo de oro, se midió su masa y se encontró un valor igual que 50 g; al medir su volumen este fue de 2.587 cm3. Calcular su densidad.

b i think it’s a water wheel turning in a stream

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.