When metal hydroxides decompose when heated, they yield oxides and water.

Here's the general reaction:

Metal Hydroxide → Metal Oxide + Water

For example:

* Cu(OH)₂ → CuO + H₂O (Copper(II) hydroxide decomposes into copper(II) oxide and water)

* 2Fe(OH)₃ → Fe₂O₃ + 3H₂O (Iron(III) hydroxide decomposes into iron(III) oxide and water)

This decomposition is often driven by the release of energy (exothermic reaction) as the hydroxide bonds break and new, more stable oxide bonds form.