Interpret the following equations in terms of 1- Numbers of representative particles(atoms and molecules).
2- Moles.
3- Masses of reactants and produces.
4- Volumes

1) Al2S3 2Al + 3S

2) C4H12 + 7O2 6H2O + 4CO2

3) Cl2 + 2KBr 2KCl + Br2

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.