Question

Is hydrogen and oxygen gas combining to form `H_2O` a chemical or physical change?

Answer 1

This is manifestly a chemical change............

Explanation:

Chemical change is characterized by the making and breaking of strong chemical bonds, and the formation of new substances.......

`H_2 + 1/2O_2 rarr H_2O`

And this representation certainly depicts the breaking STRONG `H-H` and `O=O` bonds, and the making of stronger `H-O` bonds in the water molecule.

And so, this clearly is an example of chemical change.