Which chemical is associated with a high risk of explosive reaction in contact with water?

Sodium is a highly reactive alkali metal that poses significant risks when it comes into contact with water. When sodium interacts with water, it undergoes a vigorous exothermic reaction, producing hydrogen gas and sodium hydroxide. The heat generated from this reaction can ignite the hydrogen gas, leading to an explosive situation. This characteristic makes sodium especially hazardous in environments where moisture is present.

Potassium, while also reactive with water, is even more reactive than sodium and can lead to similar explosive outcomes. Calcium and magnesium also react with water, but their reactions are less dramatic and do not typically result in explosions under standard conditions. Understanding the reactivity of these materials is essential for hazardous material handling and firefighters' safety protocols.