How can H2O be formed from hydrogen and oxygen?

Answer 1

Two atoms of hydrogen combine with one atom of oxygen to form water. Both hydrogen and oxygen are gases at room temperature, and they need to be activated in order to form H2O when combined. The activation, through a spark or flame, produces the water when these atoms are combined.

Answer 2

H2O is formed when gaseous hydrogen (H2) and oxygen (O2) combine in the presence of heat or a spark, initiating a chemical reaction that creates water vapor. The hydrogen and oxygen atoms rearrange their bonds to form water molecules (H2O), releasing energy in the process.