.
.
Limestone
can be found at many places around us: White scale in a teakettle,
in a washbasin or in a shower. Not only men use limestone as building
materials. Shells of snails, mussels and coral
reefs are made of the same material which is calcium carbonate.
Chalk
is a white porous limestone. (Nowadays blackboard
chalk is mainly made from gypsum). Calcite,
marble and marble alabaster are very clean and dense forms
of limestone. For
the experiment you need a piece of marble (Photo
1).
Material
Experiment
1.
Weigh 0.5 g of marble (Photo 1). g
2.
Place it on a tile and heat by a butan gas micro burner for 15 minutes
(Photo 2).
3.
After cooling weigh it again. If its mass is more than half of the first
one:
4. Repeat heating, cooling
and weighing. Photo
3 and 4: Limestone
("Branntkalk") after burning and after grinding
Observations
The
stone has lost it crystalline shine. Its mass is reduced from 0.5 g to
0.3 g.
Explanation
A
chemical reaction ("burning")
took place, a new substance (quick lime = Calcium oxide) was formed:
CaCO3 --------consumption of heat----------->
CaO + CO2