What is the volume of the rock?

To find the volume of the rock, subtract the initial volume of the water from the final volume of the water: 50 mL - 30 mL = 20 mL. Therefore, the volume of the rock would be equal to 20 mL or 20 cc.

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.