Is water the only thing that has surface tension?

No, many liquids have surface tension such as mercury.

Water has a high surface tension because the water molecules on the surface are pulled together by strong hydrogen bonds. That means a drop of water will "want" to have the smallest possible surface area.

Explanation:

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.