Calcium reacts with water to form calcium hydroxide and hydrogen gas alongwith heat. The reaction occurs as follows:
Ca (s)+2H2O (l)→Ca(OH)2(aq)+H2(g)+Heat
Potassium reacts with water to form potassium hydroxide and hydrogen gas alongwith heat. The reaction occurs as follows:
2K (s)+2H2O (l)→2KOH (aq)+H2(g)+Heat