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

What is the state of lithium in the reaction with water?

1. Gas

2. Liquid

3. Solid

4. Aqueous

The correct answer is: Solid

In the reaction with water, lithium is in the solid state prior to the reaction occurring. When lithium comes into contact with water, it reacts to form lithium hydroxide and hydrogen gas. The reaction is exothermic and can cause the hydrogen gas to ignite, producing bubbles. Lithium, as an alkali metal, has a relatively low density and melting point compared to other metals, allowing it to float on water. While it is solid at room temperature and retains its solid state during the initial reaction phase, the resulting products may change the state of the overall system. Therefore, the correct response reflects that lithium, before any reaction takes place, is in a solid state.