This would work good to explain the verb "boil" in some sort of language learning program I guess. The original source of this image was a water propaganda pamphlet produced by the America EPA youth outreach program (thus clearly public domain) and although the original was black and white, I painstakingly added colour to just make it a little more cliparty.
This is a completely free image Boil Water that you can download, post, and use for any purpose.
Image License: CC0 No Rights Reserved
You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission, and at no cost. This image is completely free.