Detailed Instructions: Given a scientific question, generate a correct answer to it.
See one example below:
Problem: Who proposed the theory of evolution by natural selection?
Solution: darwin
Explanation: This is a direct fact that Charles Darwin proposed the theory of evolution.

Problem: Potential energy is not only associated with the location of matter, but also with the structure of matter. even a spring on the ground has potential energy if it is what?
Solution:
compressed