Chalk lights under heating

Scientific name: Calcium carbonate decomposes under heating and the formed calcium oxide emits white light



The Chemistry of Light 10 - Chalk & Lime


by Theodore Gray

Calcium Carbonate Decomposition Reaction (Thermal)

by Jay Kumar Ahir


Wear eye protection and lab gloves.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

CaCO3 -[T]→ CaO + CO2


  1. Chalk

Step-by-step instruction

  1. Secure a piece of chalk in a jaw clamp of a laboratory stand.
  2. Heat the piece of chalk with a burner. A few minutes later the piece glows brilliant white light.

Scientific background

Chalk consists of calcium carbonate. It decomposes under heating to form calcium oxide and carbon dioxide. Calcium oxide (or quicklime) luminesces at a high temperature - heated quicklime emits photons of white light, and the energy of heat converts to the energy of light.


Published on 24 June 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst