Question

What causes light to be emitted when mixing alkali metals and water?

1) The release of energy as the alkali metals react with water
2) The formation of a chemical compound between the alkali metals and water
3) The production of hydrogen gas
4) The generation of heat

Answer 1

When alkali metals react with water, they release energy, produce hydrogen gas, and generate heat.

Step-by-step explanation:

When alkali metals react with water, they release energy, produce hydrogen gas, and generate heat. This is due to the fact that alkali metals are more easily oxidized than hydrogen. For example, when lithium reacts with water, it forms lithium hydroxide and releases hydrogen gas:

2Li + 2H2O → 2LiOH + H2

The release of energy, the formation of a chemical compound (metal hydroxide), and the production of hydrogen gas are the main reasons for the emission of light when alkali metals are mixed with water.