What is the reaction of sodium when it is placed in water?

When sodium is placed in water, it reacts in a vigorous manner. The correct observation of this reaction involves the production of hydrogen gas as the sodium dissolves. This process generates bubbles of hydrogen, which can create a fizzing effect. The reaction also produces sodium hydroxide, which is alkaline. As sodium is less dense than water, it will float and move around on the surface during the reaction, confirming that the movement is associated with the rapid fizzing and hydrogen gas formation rather than simply fizzing before disappearing.

The intense reactivity of sodium with water is a distinctive characteristic of alkali metals, and the fizzing phenomenon is part of the overall energetic reaction that can be observed. While other observations like creating a purple flame can occur in certain conditions, the fizzing and subsequent movement on the surface are the most direct and observable outcomes of sodium's reaction with water.