A sample is found to contain 66.5 % N a H C O 3 by mass. What is the mass of N a H C O 3 in 4.25 g of the sample

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.