Why is liquid water considered a requirement for life? I`ve heard about different extremofiles living on earth. Is water a requirement for life because we have not seen life survive on earth without it, is it a chemical  reason which makes life without water seem impossible? Could life exist with water, but in gas form? What makes the liquid part so important? Can life be based on other  liquids on potential exoplanets?
The reason for which water is needed for Life as we know it (and we have not been able to successfuly imagine a different model from that of DNA that has ability to self-replicate, react to the ambient, and evolve), is that water is the "universal solvent".

That means that most chemical reactions needed for life happen on a liquid environment, more specifically a water-based environment for most of them.