ok I’ll start off by telling you what I know. When things heat up the molecules beging to move faster and faster taking up more space and making the object take up more space. When they get colder the molecules slow down and take up less space. So when when water freezes why does it expand? I know you people at this site are a lot smarter than me so I hope you can help me. Just so you don’t think I am some retarded adult I’m only 17 and typed this not paying attention to grammer or spelling.
Welcome to the SDMB, Jason.
I think your question is answered in this thread, especially in beatles’s response.
Because of the weak anthropic principle 
Seriously, this contradication is the reason life on earth exists.
If solid water (or ice) compressed it would sink to the bottom of the ocean thus freezing the ocean and life would not have survived thus evovling out of the ocean and onto land.
Sorry no idea why ice does this though