Explain Displacement reaction?
Explain Neutralisation?

Displacement reaction or replacement reaction is a type of chemical reaction in which an element is replaced by another in a compound.

Neutralisation is a process when acid and base mix and react together to form salt and water.

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.

answer: they produce more slow than unicellular organisms.