Which one of these is a gas nano3 kl kcl nh3

nano3 is a solid so its not that one it has to be NH3

Explanation:

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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.