Detailed Instructions: In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 
Q: Water seeps into rocks. The water freezes and thaws. Cracks form in the rocks. Cracks also form when rocks heat up. The rocks slowly break down. 
A:
water ,rocks ,cracks 