When water is added to quicklime, a fierce exothermic reaction takes place as calcium hydroxide, slaked lime, is formed.
To prepare this demo Dr Peter Wothers ordered Calcium Carbonate blocks from a quarry in Portland which were cut up to fit in our furnace by a mason. Each block then took 48 hours to make by heating to 1000 C in the furnace in the labs in the Chemistry Department in Cambridge. During the baking, carbon dioxide is driven out and calcium oxide, quicklime, is formed. This process has been carried out for hundreds of years in the production of cements.
Peter Wothers explains more:
"I chose this reaction to illustrate our third Christmas Lecture (Earth). I love it reaction because of all the steam produced and the popping sound as bits of slaked lime ping off in all directions. It really makes us think about the nature of different minerals and exactly what 'stone' is.
"To protect the precious grass at the St Catharine’s College sports field, we put wooden boards down, covered them with plastic, and then turf. Seeing the messy aftermath, we were glad we took these precautions!"
Devised to promote the 2012 Christmas Lectures, this is one of three large-scale, chemistry demos that were too big (or too dangerous!) to perform in the Ri Lecture Theatre in front of 400 young people.
This experiment was undertaken under the supervision of professionals and should not be replicated.
More about the 2012 Christmas Lectures: richannel.org/christmas-lectures/2012/peter-wothers