Microscale Chemistry Experimentation for Teachers
Thermal decomposition of marble by a butane gas micro torch:
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Thermal decomposition of marble by a butane gas micro torch:
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Left
and photo 2: A fingertip-sized piece of marble is weighed on a two
pan balance.
Photo
3: It is placed on a heat resistant tile and heated by a butane gas
torch for about 10 minutes.
During
this time the marble is transformed into a white substance which has lost
half of its mass.
Right:
After cooling drops of water are added. In an exothermic reaction the volume
of the stone increases.
Adding
more water a milky suspension is obtained which shows a pink colour after
adding a drop of phenolphthalein.
Explanations:
During thermal decomposition ("burning") of marble CaCO3 is
transformed into CaO.
Calcium
oxide reacts with water in an exothermic reaction leaving calcium hydroxide
= Ca(OH)2.
Ca(OH)2
and water form an alkaline solution which is indicated by the colour of
phenolphthalein.