International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What happens to sodium when it reacts with water?

1. Sodium catches fire

2. Sodium dissolves completely

3. Sodium produces a loud noise

4. Sodium moves around and melts

The correct answer is: Sodium moves around and melts

When sodium reacts with water, it undergoes a vigorous exothermic reaction, producing sodium hydroxide and hydrogen gas. During this process, sodium does indeed move around on the surface of the water, which is often quite exciting to observe. The heat produced in the reaction leads to the melting of sodium, as it has a relatively low melting point of about 98 degrees Celsius. While sodium does produce some noise due to the rapid evolution of hydrogen gas and the movement as it interacts with the water, these effects are secondary to the noticeable movement and melting of sodium itself. The strong reactivity of sodium with water is evident as it fizzes and moves across the water's surface, which is characteristic of this type of reaction.