Reactivity of alkaline earth metals towards water
Do not forget solubility effects involving the hydroxide product.  Magnesium is plenty electropositive enough to decompose water, only to passivate with a hydroxide that has limited solubility (you can detect the presence of some reaction by decanting the liquid and then adding phenolphthalein, or by carefully looking for a few hydrogen bubbles during the reaction).  Put magnesium in methanol, which is less protic than water; the methoxide is less passivating and you can actually bring the alcohol to a boil!  See https://www.google.com/url?sa=t&amp;source=web&amp;rct=j&amp;url=https://m.youtube.com/watch%3Fv%3DNMfs3e9OdZQ&amp;ved=0ahUKEwjlnLOxpPDWAhVDKiYKHVFwB5wQwqsBCCgwAA&amp;usg=AOvVaw2TaAZjVq0m8EHL-JluhxGn.