text: *Calcium carbonate (limestone or chalk) decomposes into calcium oxide and carbon dioxide when heated. The chemical reaction is as follows:
  ::CaCO → CaO + CO
  :The reaction is used to make quick lime, which is an industrially important product.
  :Another example of thermal decomposition is 2Pb(NO) → 2PbO + O + 4NO.
  *Some oxides, especially of weakly electropositive metals decompose when heated to high enough temperature. A classical example is the decomposition of mercuric oxide to give oxygen and mercury metal. The reaction was used by Joseph Priestley to prepare samples of gaseous oxygen for the first time.
  *When water is heated to well over , a small percentage of it will decompose into OH, monatomic oxygen, monatomic hydrogen, O, and H.
  *The compound with the highest known decomposition temperature is carbon monoxide at ≈3870 °C (≈7000 °F).