In order to form water, oxygen must react with hydrogen.

When hydrogen and oxygen do react to form water, a great deal of energy is released.

The hydrogen is combusted with oxygen to form water and heat.

The example of hydrogen and oxygen, forming water is perhaps a benchmark for your question.

Much heat is released when hydrogen and oxygen recombine to form water.

This means molecular hydrogen, H, is combined with oxygen to form water.

To make the features, ice melted to form liquid water, then refroze.

These two gasses can be combined to form water.

Then the hydrogen and oxygen undergo combustion due to the excessive heat to form water again.

These will react to form sodium chloride and water.