Water as solvent for salts and gases
Water is an excellent solvent of ionic and polar substances because it is a polar liquid.
Information and ideas:
Normally a substance is more soluble in polar solvents such as water, the more polar groups that substance has. Near-critical water however has similar solubility properties as non-polar organic solvents. The temperature dependency of solubility is a good example for looking at the difference between speed and equilibrium.